Removal of dyes from Wastewater by Cationic Bentonite Polymer Nagapan S

Removal of dyes from Wastewater by Cationic Bentonite Polymer
Nagapan S; Gengan R M; Krishnan A
Department of Chemistry, Faculty of Applied Science, Durban University of Technology
Abstract
A novel cationic polymer; Epichlorohydrin-Sarcosine (SCP) was synthesized from epichlorohydrin, ethylenediamine and sarcosine. The SCP was characterized by FT-IR, TGA and Zeta potential. The SCP was modified with bentonite to form a cationic bentonite polymer (CBP); which was characterized by FT-IR. The adsorption kinetics of three bi-functional reactive dyes, viz., Reactive Blue 222 (RB), Reactive Red 195 (RR) and Reactive Yellow 145 (RY) were studied under different conditions, in order to identify the CBP’s ability to remove the coloured dyes from wastewater. The results indicated that the dyes adsorb at different rates; RB adsorbs the fastest and RR adsorbs the slowest. The results obtained were applied to pseudo first-order and pseudo second-order kinetic rate equations and it was found that the adsorption process follows a two-step kinetic model. As the adsorption process proceeds, it is controlled by the intraparticle diffusion model. The results were also applied into the Freundlich and Langmuir isotherms, and fitted both but the Langmuir showed better monolayer coverage. The Arrhenius equation showed that the activation energy for RR was higher than that for RY. Thermodynamic parameters such as entropy, enthalpy and Gibb’s free energy were determined. For RR the adsorption process is spontaneous at low temperatures but RY it is spontaneous at high temperatures. Thermodynamic properties could not be determined for RB because of its high adsorption rate. Industrial effluent was tested using CBP and the adsorption process was successful when the effluent was acidified. The CBP is a cheap and effective adsorbent but is ineffective in alkaline conditions.

Introduction
Dyes
Textile wastewater is one of the important effluents that needs to be recycled. In the industry, textile materials were dyed with natural colouring compounds of plant and animal origin. These natural dyes were biodegradable and were never a threat to the environment. PEVuZE5vdGU+PENpdGU+PEF1dGhvcj5QYWw8L0F1dGhvcj48WWVhcj4yMDA5PC9ZZWFyPjxSZWNO
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ADDIN EN.CITE.DATA (Pal, Ghosh et al. 2009)
However, procurement of these natural dyes in large quantities was always a problem; hence these dyes eventually gave way to synthetic dyes, which can be prepared from coal/petroleum-based chemicals. PEVuZE5vdGU+PENpdGU+PEF1dGhvcj5QYWw8L0F1dGhvcj48WWVhcj4yMDA5PC9ZZWFyPjxSZWNO
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ADDIN EN.CITE.DATA (Pal, Ghosh et al. 2009)
Synthetic dyes are among the most commonly used pollutants which appear in various industries, such as dyestuff, textiles, leather, and paper. These dyes exhibit a wide range of different chemical structures, primarily based on substituted aromatic and heterocyclic groups. ADDIN EN.CITE <EndNote><Cite><Author>Nesic</Author><Year>2012</Year><RecNum>14</RecNum><DisplayText>(Nesic, Velickovic et al. 2012)</DisplayText><record><rec-number>14</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427815″>14</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Nesic, A. R.</author><author>Velickovic, S. J.</author><author>Antonovic, D. G.</author></authors></contributors><auth-address>Vinca Institute of Nuclear Sciences, University of Belgrade, PO Box 522, RS – 11001 Belgrade, Serbia. [email protected]</auth-address><titles><title>Characterization of chitosan/montmorillonite membranes as adsorbents for Bezactiv Orange V-3R dye</title><secondary-title>J Hazard Mater</secondary-title><alt-title>Journal of hazardous materials</alt-title></titles><periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></periodical><alt-periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></alt-periodical><pages>256-63</pages><volume>209-210</volume><keywords><keyword>Adsorption</keyword><keyword>Bentonite/*chemistry</keyword><keyword>Chitosan/*chemistry</keyword><keyword>Coloring Agents/*chemistry</keyword><keyword>Diffusion</keyword><keyword>Kinetics</keyword><keyword>*Membranes, Artificial</keyword><keyword>Microscopy, Electron, Scanning</keyword><keyword>Spectroscopy, Fourier Transform Infrared</keyword><keyword>Temperature</keyword><keyword>Thermogravimetry</keyword></keywords><dates><year>2012</year><pub-dates><date>Mar 30</date></pub-dates></dates><isbn>1873-3336 (Electronic) 0304-3894 (Linking)</isbn><accession-num>22305598</accession-num><urls><related-urls><url>http://www.ncbi.nlm.nih.gov/pubmed/22305598</url></related-urls></urls><electronic-resource-num>10.1016/j.jhazmat.2012.01.020</electronic-resource-num></record></Cite></EndNote>(Nesic, Velickovic et al. 2012)
There are many different types of dyes and their structural diversity come from the use of different chromophoric groups and different application technologies (techniques used for dyeing fibres). ADDIN EN.CITE <EndNote><Cite><Author>Cuoto</Author><Year>2009</Year><RecNum>74</RecNum><DisplayText>(Cuoto 2009)</DisplayText><record><rec-number>74</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1402866935″>74</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Susanna Rodriguez Cuoto</author></authors></contributors><titles><title>Dye removed by immobilized fungi</title><secondary-title>Biotechnology advances</secondary-title></titles><periodical><full-title>Biotechnology advances</full-title></periodical><pages>227-235</pages><volume>27</volume><dates><year>2009</year></dates><urls></urls><electronic-resource-num>10.1016/j.biotechadv.2008.12.001</electronic-resource-num></record></Cite></EndNote>(Cuoto 2009)
Reactive Dyes
Reactive dyes are commonly used in textile industries to dye cellulose fibres and are the most important single group of dyes used in textile industry, with a trend of increasing usage. ADDIN EN.CITE <EndNote><Cite><Author>Valderrama</Author><Year>2008</Year><RecNum>27</RecNum><DisplayText>(Valderrama, Cortina et al. 2008)</DisplayText><record><rec-number>27</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427886″>27</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Valderrama, C.</author><author>Cortina, J. L.</author><author>Farran, A.</author><author>Gamisans, X.</author><author>de las Heras, F. X.</author></authors></contributors><titles><title>Evaluation of hyper-cross-linked polymeric sorbents (Macronet MN200 and MN300) on dye (Acid red 14) removal process</title><secondary-title>Reactive and Functional Polymers</secondary-title></titles><periodical><full-title>Reactive and Functional Polymers</full-title></periodical><pages>679-691</pages><volume>68</volume><number>3</number><dates><year>2008</year></dates><isbn>13815148</isbn><urls></urls><electronic-resource-num>10.1016/j.reactfunctpolym.2007.11.005</electronic-resource-num></record></Cite></EndNote>(Valderrama, Cortina et al. 2008) These dyes are characterized by nitrogen to nitrogen double bonds (N=N azo bonds), and the colour of the dyes are due to the azo bond present and are also associated with the chromophores present. ADDIN EN.CITE <EndNote><Cite><Author>Janaki</Author><Year>2012</Year><RecNum>7</RecNum><DisplayText>(Janaki, Oh et al. 2012)</DisplayText><record><rec-number>7</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427782″>7</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Janaki, V.</author><author>Oh, Byung-Taek</author><author>Vijayaraghavan, K.</author><author>Kim, Jin-Won</author><author>Kim, Seol Ah</author><author>Ramasamy, A. K.</author><author>Kamala-Kannan, Seralathan</author></authors></contributors><titles><title>Application of bacterial extracellular polysaccharides/polyaniline composite for the treatment of Remazol effluent</title><secondary-title>Carbohydrate Polymers</secondary-title></titles><periodical><full-title>Carbohydrate Polymers</full-title></periodical><pages>1002-1008</pages><volume>88</volume><number>3</number><dates><year>2012</year></dates><isbn>01448617</isbn><urls></urls><electronic-resource-num>10.1016/j.carbpol.2012.01.045</electronic-resource-num></record></Cite></EndNote>(Janaki, Oh et al. 2012) The chromophore and functional group (auxochrome), anchors the dye into or within the fibres to intensify the colour. ADDIN EN.CITE <EndNote><Cite><Author>Zahrim</Author><Year>2011</Year><RecNum>17</RecNum><DisplayText>(Zahrim, Tizaoui et al. 2011)</DisplayText><record><rec-number>17</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427828″>17</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Zahrim, A. Y.</author><author>Tizaoui, C.</author><author>Hilal, N.</author></authors></contributors><titles><title>Coagulation with polymers for nanofiltration pre-treatment of highly concentrated dyes: A review</title><secondary-title>Desalination</secondary-title></titles><periodical><full-title>Desalination</full-title></periodical><pages>1-16</pages><volume>266</volume><number>1-3</number><dates><year>2011</year></dates><isbn>00119164</isbn><urls></urls><electronic-resource-num>10.1016/j.desal.2010.08.012</electronic-resource-num></record></Cite></EndNote>(Zahrim, Tizaoui et al. 2011)
The reaction occurs by the formation of covalent bond, which is much more resistant to unusual conditions of use than the physicochemical bond between other classes of dyes and cellulose fibre. The reactive systems of these dyes react with ionized hydroxyl groups on the cellulose fibre. However, hydroxyl ions present in the dye bath can compete with the cellulose substrate, resulting in a percentage of hydrolysed dyes which can no longer react with the cellulose fibre. ADDIN EN.CITE <EndNote><Cite><Author>Zahrim</Author><Year>2011</Year><RecNum>17</RecNum><DisplayText>(Zahrim, Tizaoui et al. 2011)</DisplayText><record><rec-number>17</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427828″>17</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Zahrim, A. Y.</author><author>Tizaoui, C.</author><author>Hilal, N.</author></authors></contributors><titles><title>Coagulation with polymers for nanofiltration pre-treatment of highly concentrated dyes: A review</title><secondary-title>Desalination</secondary-title></titles><periodical><full-title>Desalination</full-title></periodical><pages>1-16</pages><volume>266</volume><number>1-3</number><dates><year>2011</year></dates><isbn>00119164</isbn><urls></urls><electronic-resource-num>10.1016/j.desal.2010.08.012</electronic-resource-num></record></Cite></EndNote>(Zahrim, Tizaoui et al. 2011) Thus, 10–50% of the initial dye load will be present in the dye bath, giving rise to a highly coloured effluent. ADDIN EN.CITE <EndNote><Cite><Author>Janaki</Author><Year>2012</Year><RecNum>7</RecNum><DisplayText>(Janaki, Oh et al. 2012)</DisplayText><record><rec-number>7</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427782″>7</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Janaki, V.</author><author>Oh, Byung-Taek</author><author>Vijayaraghavan, K.</author><author>Kim, Jin-Won</author><author>Kim, Seol Ah</author><author>Ramasamy, A. K.</author><author>Kamala-Kannan, Seralathan</author></authors></contributors><titles><title>Application of bacterial extracellular polysaccharides/polyaniline composite for the treatment of Remazol effluent</title><secondary-title>Carbohydrate Polymers</secondary-title></titles><periodical><full-title>Carbohydrate Polymers</full-title></periodical><pages>1002-1008</pages><volume>88</volume><number>3</number><dates><year>2012</year></dates><isbn>01448617</isbn><urls></urls><electronic-resource-num>10.1016/j.carbpol.2012.01.045</electronic-resource-num></record></Cite></EndNote>(Janaki, Oh et al. 2012)

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Figure 1: (a) Chemical structure of BR. (b) Chemical structure of RR. Chemical Structure of RY
Effluent
The effluent is generally alkaline, high in BOD and suspended solids, and is large in volume due to the large amounts of water needed for dying and washing. The annual discharge of dye effluent is estimated at around 50,000 tons per year. ADDIN EN.CITE <EndNote><Cite><Author>Trang Si Trung</Author><Year>2003</Year><RecNum>15</RecNum><DisplayText>(Trang Si Trung 2003)</DisplayText><record><rec-number>15</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427817″>15</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Trang Si Trung, Chuen-How Ng &amp;Willem F. Stevens</author></authors></contributors><titles><title>characterization of decrystallized chitosan and its appication in biosorption of textile dyes</title><secondary-title>Biotechnology Letters</secondary-title></titles><periodical><full-title>Biotechnology Letters</full-title></periodical><pages>1185–1190,</pages><volume>25</volume><dates><year>2003</year></dates><urls></urls></record></Cite></EndNote>(Trang Si Trung 2003)
Furthermore, some dyes and their reaction products, such as aromatic amines, possess high carcinogenicity. ADDIN EN.CITE <EndNote><Cite><Author>Li</Author><Year>2009</Year><RecNum>1</RecNum><DisplayText>(Li, Yue et al. 2009)</DisplayText><record><rec-number>1</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427754″>1</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Li, Q.</author><author>Yue, Q. Y.</author><author>Su, Y.</author><author>Gao, B. Y.</author><author>Li, J.</author></authors></contributors><auth-address>School of Environmental Science and Engineering, Shandong University, Jinan, Shandong, PR China. [email protected]</auth-address><titles><title>Two-step kinetic study on the adsorption and desorption of reactive dyes at cationic polymer/bentonite</title><secondary-title>J Hazard Mater</secondary-title><alt-title>Journal of hazardous materials</alt-title></titles><periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></periodical><alt-periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></alt-periodical><pages>1170-8</pages><volume>165</volume><number>1-3</number><keywords><keyword>Adsorption</keyword><keyword>Azo Compounds/isolation &amp; purification</keyword><keyword>Bentonite/*chemistry</keyword><keyword>Cations</keyword><keyword>Coloring Agents/*isolation &amp; purification</keyword><keyword>Diffusion</keyword><keyword>Kinetics</keyword><keyword>Polymers/*chemistry</keyword><keyword>Sulfonamides/isolation &amp; purification</keyword><keyword>Thermodynamics</keyword></keywords><dates><year>2009</year><pub-dates><date>Jun 15</date></pub-dates></dates><isbn>1873-3336 (Electronic) 0304-3894 (Linking)</isbn><accession-num>19081187</accession-num><urls><related-urls><url>http://www.ncbi.nlm.nih.gov/pubmed/19081187</url></related-urls></urls><electronic-resource-num>10.1016/j.jhazmat.2008.10.110</electronic-resource-num></record></Cite></EndNote>(Li, Yue et al. 2009) The presence of residual dyes in surface water is aesthetically undesirable and causes annoyance to the aquatic biosphere due to the reduction of sunlight penetration and depletion of the dissolved oxygen. ADDIN EN.CITE <EndNote><Cite><Author>Zahrim</Author><Year>2011</Year><RecNum>17</RecNum><DisplayText>(Zahrim, Tizaoui et al. 2011)</DisplayText><record><rec-number>17</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427828″>17</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Zahrim, A. Y.</author><author>Tizaoui, C.</author><author>Hilal, N.</author></authors></contributors><titles><title>Coagulation with polymers for nanofiltration pre-treatment of highly concentrated dyes: A review</title><secondary-title>Desalination</secondary-title></titles><periodical><full-title>Desalination</full-title></periodical><pages>1-16</pages><volume>266</volume><number>1-3</number><dates><year>2011</year></dates><isbn>00119164</isbn><urls></urls><electronic-resource-num>10.1016/j.desal.2010.08.012</electronic-resource-num></record></Cite></EndNote>(Zahrim, Tizaoui et al. 2011) Dyes absorb and reflect sunlight that enters the water, which interferes with the growth of bacteria, limiting it to levels insufficient to biologically degrade impurities in the water. ADDIN EN.CITE <EndNote><Cite><Author>Crini</Author><Year>2008</Year><RecNum>32</RecNum><DisplayText>(Crini 2008)</DisplayText><record><rec-number>32</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427910″>32</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Crini, Grégorio</author></authors></contributors><titles><title>Kinetic and equilibrium studies on the removal of cationic dyes from aqueous solution by adsorption onto a cyclodextrin polymer</title><secondary-title>Dyes and Pigments</secondary-title></titles><periodical><full-title>Dyes and Pigments</full-title></periodical><pages>415-426</pages><volume>77</volume><number>2</number><dates><year>2008</year></dates><isbn>01437208</isbn><urls></urls><electronic-resource-num>10.1016/j.dyepig.2007.07.001</electronic-resource-num></record></Cite></EndNote>(Crini 2008) Some of the reactive dyes are toxic and pose a serious threat to aquatic biota and human beings. Therefore, there is a considerable need to treat reactive dye effluents before their discharge into receiving waters. ADDIN EN.CITE <EndNote><Cite><Author>Janaki</Author><Year>2012</Year><RecNum>7</RecNum><DisplayText>(Janaki, Oh et al. 2012)</DisplayText><record><rec-number>7</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427782″>7</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Janaki, V.</author><author>Oh, Byung-Taek</author><author>Vijayaraghavan, K.</author><author>Kim, Jin-Won</author><author>Kim, Seol Ah</author><author>Ramasamy, A. K.</author><author>Kamala-Kannan, Seralathan</author></authors></contributors><titles><title>Application of bacterial extracellular polysaccharides/polyaniline composite for the treatment of Remazol effluent</title><secondary-title>Carbohydrate Polymers</secondary-title></titles><periodical><full-title>Carbohydrate Polymers</full-title></periodical><pages>1002-1008</pages><volume>88</volume><number>3</number><dates><year>2012</year></dates><isbn>01448617</isbn><urls></urls><electronic-resource-num>10.1016/j.carbpol.2012.01.045</electronic-resource-num></record></Cite></EndNote>(Janaki, Oh et al. 2012) The release of these effluents causes coloration of surface waters and the coloured effluent blocks the photosynthetic bacteria and aquatic plants from sunlight, interfering with the ecology of the receiving water. ADDIN EN.CITE <EndNote><Cite><Author>Dotto</Author><Year>2011</Year><RecNum>6</RecNum><DisplayText>(Dotto and Pinto 2011)</DisplayText><record><rec-number>6</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427780″>6</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Dotto, G. L.</author><author>Pinto, L. A.</author></authors></contributors><auth-address>Unit Operation Laboratory, School of Chemistry and Food, Federal University of Rio Grande – FURG, 475 Engenheiro Alfredo Huch Street, 96201-900 Rio Grande, RS, Brazil.</auth-address><titles><title>Adsorption of food dyes acid blue 9 and food yellow 3 onto chitosan: stirring rate effect in kinetics and mechanism</title><secondary-title>J Hazard Mater</secondary-title><alt-title>Journal of hazardous materials</alt-title></titles><periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></periodical><alt-periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></alt-periodical><pages>164-70</pages><volume>187</volume><number>1-3</number><keywords><keyword>Adsorption</keyword><keyword>Chitosan/*chemistry</keyword><keyword>Coloring Agents/*chemistry</keyword><keyword>*Food</keyword><keyword>Kinetics</keyword></keywords><dates><year>2011</year><pub-dates><date>Mar 15</date></pub-dates></dates><isbn>1873-3336 (Electronic) 0304-3894 (Linking)</isbn><accession-num>21255919</accession-num><urls><related-urls><url>http://www.ncbi.nlm.nih.gov/pubmed/21255919</url></related-urls></urls><electronic-resource-num>10.1016/j.jhazmat.2011.01.016</electronic-resource-num></record></Cite></EndNote>(Dotto and Pinto 2011) Most of dyes released during textiles, clothing, printing, and dyeing processes are considered as hazardous and toxic to some organisms and may cause allergic dermatitis, skin irritation and are mutagenic to human and aquatic organisms.PEVuZE5vdGU+PENpdGU+PEF1dGhvcj5aaG91PC9BdXRob3I+PFllYXI+MjAxMTwvWWVhcj48UmVj
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Tm90ZT4A
ADDIN EN.CITE.DATA (Zhou, Jin et al. 2011)
In addition, due to its high water-solubility, it is estimated that 10–20% of reactive dye remains in wastewater during production and nearly 50% of reactive dyes may be lost to the effluents during dyeing processes, and their removal from effluent is difficult by conventional physicochemical and biological treatment methods. ADDIN EN.CITE <EndNote><Cite><Author>Li</Author><Year>2009</Year><RecNum>1</RecNum><DisplayText>(Li, Yue et al. 2009)</DisplayText><record><rec-number>1</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427754″>1</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Li, Q.</author><author>Yue, Q. Y.</author><author>Su, Y.</author><author>Gao, B. Y.</author><author>Li, J.</author></authors></contributors><auth-address>School of Environmental Science and Engineering, Shandong University, Jinan, Shandong, PR China. [email protected]</auth-address><titles><title>Two-step kinetic study on the adsorption and desorption of reactive dyes at cationic polymer/bentonite</title><secondary-title>J Hazard Mater</secondary-title><alt-title>Journal of hazardous materials</alt-title></titles><periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></periodical><alt-periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></alt-periodical><pages>1170-8</pages><volume>165</volume><number>1-3</number><keywords><keyword>Adsorption</keyword><keyword>Azo Compounds/isolation &amp; purification</keyword><keyword>Bentonite/*chemistry</keyword><keyword>Cations</keyword><keyword>Coloring Agents/*isolation &amp; purification</keyword><keyword>Diffusion</keyword><keyword>Kinetics</keyword><keyword>Polymers/*chemistry</keyword><keyword>Sulfonamides/isolation &amp; purification</keyword><keyword>Thermodynamics</keyword></keywords><dates><year>2009</year><pub-dates><date>Jun 15</date></pub-dates></dates><isbn>1873-3336 (Electronic) 0304-3894 (Linking)</isbn><accession-num>19081187</accession-num><urls><related-urls><url>http://www.ncbi.nlm.nih.gov/pubmed/19081187</url></related-urls></urls><electronic-resource-num>10.1016/j.jhazmat.2008.10.110</electronic-resource-num></record></Cite></EndNote>(Li, Yue et al. 2009) The resulting anaerobic condition eventually ruins these water bodies.PEVuZE5vdGU+PENpdGU+PEF1dGhvcj5QYWw8L0F1dGhvcj48WWVhcj4yMDA5PC9ZZWFyPjxSZWNO
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ADDIN EN.CITE.DATA (Zhou, Jin et al. 2011) A wide range of structurally diverse dyes have been used in textile industries and therefore the effluents from these textile companies vary in composition. Dye house effluent is generally very stable to light and air oxidation. ADDIN EN.CITE <EndNote><Cite><Author>Baburaj</Author><Year>2012</Year><RecNum>65</RecNum><DisplayText>(Baburaj, Aravindakumar et al. 2012)</DisplayText><record><rec-number>65</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400428068″>65</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Baburaj, M. S.</author><author>Aravindakumar, C. T.</author><author>Sreedhanya, S.</author><author>Thomas, A. P.</author><author>Aravind, Usha K.</author></authors></contributors><titles><title>Treatment of model textile effluents with PAA/CHI and PAA/PEI composite membranes</title><secondary-title>Desalination</secondary-title></titles><periodical><full-title>Desalination</full-title></periodical><pages>72-79</pages><volume>288</volume><dates><year>2012</year></dates><isbn>00119164</isbn><urls></urls><electronic-resource-num>10.1016/j.desal.2011.12.015</electronic-resource-num></record></Cite></EndNote>(Baburaj, Aravindakumar et al. 2012)
Treatment methods
The standard industrial wastewater treatment process using activated sludge and sedimentation efficiently decreases BOD values and suspended solids but is poor in decolourization. The economic and efficient removal of dyes from the wastewater is of major importance, particularly as national and international legislation is becoming increasingly stringent to ensure environmental protection against polluting industrial wastewater. There is therefore a need to develop technology that is both inexpensive and biocompatible. ADDIN EN.CITE <EndNote><Cite><Author>Trang Si Trung</Author><Year>2003</Year><RecNum>15</RecNum><DisplayText>(Trang Si Trung 2003)</DisplayText><record><rec-number>15</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427817″>15</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Trang Si Trung, Chuen-How Ng &amp;Willem F. Stevens</author></authors></contributors><titles><title>characterization of decrystallized chitosan and its appication in biosorption of textile dyes</title><secondary-title>Biotechnology Letters</secondary-title></titles><periodical><full-title>Biotechnology Letters</full-title></periodical><pages>1185–1190,</pages><volume>25</volume><dates><year>2003</year></dates><urls></urls></record></Cite></EndNote>(Trang Si Trung 2003)
Dyes, especially reactive dyes can escape from conventional wastewater treatment because they are generally designed to withstand microbial, chemical and photolytic degradation. Besides dyes, dyeing wastewater also contains chemical auxiliaries like salts, heavy metals, dispersing agents, smoothing agents, surfactants (i.e. to minimise aggregation of dyes) etc. which makes dyeing wastewater more complex to treat and raises the need for more than a single treatment step. ADDIN EN.CITE <EndNote><Cite><Author>Zahrim</Author><Year>2011</Year><RecNum>17</RecNum><DisplayText>(Zahrim, Tizaoui et al. 2011)</DisplayText><record><rec-number>17</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427828″>17</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Zahrim, A. Y.</author><author>Tizaoui, C.</author><author>Hilal, N.</author></authors></contributors><titles><title>Coagulation with polymers for nanofiltration pre-treatment of highly concentrated dyes: A review</title><secondary-title>Desalination</secondary-title></titles><periodical><full-title>Desalination</full-title></periodical><pages>1-16</pages><volume>266</volume><number>1-3</number><dates><year>2011</year></dates><isbn>00119164</isbn><urls></urls><electronic-resource-num>10.1016/j.desal.2010.08.012</electronic-resource-num></record></Cite></EndNote>(Zahrim, Tizaoui et al. 2011) The treatment of wastewater has long been a major concern in the environmental field. The total dye consumption of the textile industry worldwide is in excess of 107 kg per year, and an estimated 90% of this ends up on fabrics. So, approximately one million kilograms per year of dyes is discharged into water streams by the textile industry. Dye producers and users are interested in stability and fastness and, consequently, are producing dyestuffs which are more difficult to degrade after use.PEVuZE5vdGU+PENpdGU+PEF1dGhvcj5DZXN0YXJpPC9BdXRob3I+PFllYXI+MjAwNTwvWWVhcj48
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ADDIN EN.CITE.DATA (Cestari, Vieira et al. 2005)

There are many alternative treatment processes that can be used for the removal of dyes from wastewater. ADDIN EN.CITE <EndNote><Cite><Author>Li</Author><Year>2009</Year><RecNum>1</RecNum><DisplayText>(Li, Yue et al. 2009)</DisplayText><record><rec-number>1</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427754″>1</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Li, Q.</author><author>Yue, Q. Y.</author><author>Su, Y.</author><author>Gao, B. Y.</author><author>Li, J.</author></authors></contributors><auth-address>School of Environmental Science and Engineering, Shandong University, Jinan, Shandong, PR China. [email protected]</auth-address><titles><title>Two-step kinetic study on the adsorption and desorption of reactive dyes at cationic polymer/bentonite</title><secondary-title>J Hazard Mater</secondary-title><alt-title>Journal of hazardous materials</alt-title></titles><periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></periodical><alt-periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></alt-periodical><pages>1170-8</pages><volume>165</volume><number>1-3</number><keywords><keyword>Adsorption</keyword><keyword>Azo Compounds/isolation &amp; purification</keyword><keyword>Bentonite/*chemistry</keyword><keyword>Cations</keyword><keyword>Coloring Agents/*isolation &amp; purification</keyword><keyword>Diffusion</keyword><keyword>Kinetics</keyword><keyword>Polymers/*chemistry</keyword><keyword>Sulfonamides/isolation &amp; purification</keyword><keyword>Thermodynamics</keyword></keywords><dates><year>2009</year><pub-dates><date>Jun 15</date></pub-dates></dates><isbn>1873-3336 (Electronic) 0304-3894 (Linking)</isbn><accession-num>19081187</accession-num><urls><related-urls><url>http://www.ncbi.nlm.nih.gov/pubmed/19081187</url></related-urls></urls><electronic-resource-num>10.1016/j.jhazmat.2008.10.110</electronic-resource-num></record></Cite></EndNote>(Li, Yue et al. 2009) Several techniques are available for the treatment of the dyes such as an electrochemical technique that destroy the colour groups, a bio-degradation process mineralising the colourless organic intermediates, chemical oxidation including homogeneous and heterogeneous photocatalytic oxidation.PEVuZE5vdGU+PENpdGU+PEF1dGhvcj5aaG91PC9BdXRob3I+PFllYXI+MjAxMTwvWWVhcj48UmVj
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Tm90ZT4A
ADDIN EN.CITE.DATA (Zhou, Jin et al. 2011) Physicochemical methods such as coagulation and flocculation, membrane separation and advanced oxidation, may be efficient for the removal of dyes, but those techniques are so expensive that they cannot be widely applied on a large scale, especially in developing countries. The biological treatment of dye effluents may result in the generation of colourless dead-end aromatic amines, which are generally more toxic than the parent compound.PEVuZE5vdGU+PENpdGU+PEF1dGhvcj5HYW88L0F1dGhvcj48WWVhcj4yMDExPC9ZZWFyPjxSZWNO
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ZT4A
ADDIN EN.CITE.DATA (Gao, Zhang et al. 2011) An effective method for removal of dyes from wastewater is adsorption, due to its simplicity and high efficiency, as well as the availability of a wide range of adsorbents. ADDIN EN.CITE <EndNote><Cite><Author>Yesi</Author><Year>2010</Year><RecNum>79</RecNum><DisplayText>(Yesi, Sisnandy et al. 2010)</DisplayText><record><rec-number>79</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1405352806″>79</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Yesi,</author><author>Sisnandy, Fiona Patricia</author><author>Ju, Yi-Hsu</author><author>Soetaredjo, Felycia Edi</author><author>Ismadji, Suryadi</author></authors></contributors><titles><title>Adsorption of Acid Blue 129 from Aqueous Solutions onto Raw and Surfactant-modified Bentonite: Application of Temperature-dependent Forms of Adsorption Isotherms</title><secondary-title>Adsorption Science &amp; Technology</secondary-title></titles><periodical><full-title>Adsorption Science &amp; Technology</full-title></periodical><pages>847-868</pages><volume>28</volume><number>10</number><dates><year>2010</year></dates><publisher>Multi Science Publishing</publisher><isbn>0263-6174</isbn><urls><related-urls><url>http://dut.summon.serialssolutions.com/2.0.0/link/0/eLvHCXMwTV1BCgIxDCziCwTF435goelm2_QsriIeXcRj0iZH_3-0FQ_eJh8YZmBm4txgnph8M9ON6RA8Fz9pny2fiyHTN0DzXPF5z69buPyx-bJzG33v3bqcH6fr-HsGMJbUE-dYovXtuIzUFECdpiSkc0RjVpB2RxIJKDbXOWaQLD4pKXDFkjIYHNy2GWo9uqEGVDbNqA2lYCQQGUpvvTR5g_UD3TsvMA</url><url>http://multi-science.metapress.com/content/425t0406k0808011/?genre=article&amp;id=doi%3a10.1260%2f0263-6174.28.10.847</url></related-urls></urls><electronic-resource-num>10.1260/0263-6174.28.10.847</electronic-resource-num></record></Cite></EndNote>(Yesi, Sisnandy et al. 2010)
Adsorption
Adsorption has been found to be superior to other techniques for water re-use in terms of initial cost, flexibility and simplicity of design, ease of operation and insensitivity include clay materials, zeolites, siliceous materials, agricultural wastes, industrial by-products and biomass. Much attention has recently been focused on polymers and natural molecules. ADDIN EN.CITE <EndNote><Cite><Author>Crini</Author><Year>2008</Year><RecNum>32</RecNum><DisplayText>(Crini 2008)</DisplayText><record><rec-number>32</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427910″>32</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Crini, Grégorio</author></authors></contributors><titles><title>Kinetic and equilibrium studies on the removal of cationic dyes from aqueous solution by adsorption onto a cyclodextrin polymer</title><secondary-title>Dyes and Pigments</secondary-title></titles><periodical><full-title>Dyes and Pigments</full-title></periodical><pages>415-426</pages><volume>77</volume><number>2</number><dates><year>2008</year></dates><isbn>01437208</isbn><urls></urls><electronic-resource-num>10.1016/j.dyepig.2007.07.001</electronic-resource-num></record></Cite></EndNote>(Crini 2008)
As an efficient and economic process, adsorption with alternative adsorbents has been investigated for the treatment of dyes in recent years.PEVuZE5vdGU+PENpdGU+PEF1dGhvcj5MaTwvQXV0aG9yPjxZZWFyPjIwMTA8L1llYXI+PFJlY051
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ADDIN EN.CITE.DATA (Singh, Sharma et al. 2009)
Traditional adsorbents like activated carbon have been investigated and used at industrial scale applications. The major disadvantage of the use of activated carbon is the need of thermal dye destruction and thermal activation of the adsorbent when exhausted. Activated carbon is difficult and expensive to come across, because of third the Environmental Protection Agency (EPA) has limited the use of activated carbon for the removal of dyes from wastewater. One of the possibilities to overcome this problem is the use of improved polymeric sorbents as a new family of polymeric resins. ADDIN EN.CITE <EndNote><Cite><Author>Valderrama</Author><Year>2008</Year><RecNum>27</RecNum><DisplayText>(Valderrama, Cortina et al. 2008)</DisplayText><record><rec-number>27</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427886″>27</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Valderrama, C.</author><author>Cortina, J. L.</author><author>Farran, A.</author><author>Gamisans, X.</author><author>de las Heras, F. X.</author></authors></contributors><titles><title>Evaluation of hyper-cross-linked polymeric sorbents (Macronet MN200 and MN300) on dye (Acid red 14) removal process</title><secondary-title>Reactive and Functional Polymers</secondary-title></titles><periodical><full-title>Reactive and Functional Polymers</full-title></periodical><pages>679-691</pages><volume>68</volume><number>3</number><dates><year>2008</year></dates><isbn>13815148</isbn><urls></urls><electronic-resource-num>10.1016/j.reactfunctpolym.2007.11.005</electronic-resource-num></record></Cite></EndNote>(Valderrama, Cortina et al. 2008)
Cationic Polymer
Cationic polymers (CP), which comprise organic cations containing nonpolar groups, are suitable for rendering clays less polar and hence more hydrophobic. And compared with traditional organobentonites, cationic polymer-loaded bentonites involve much lower cost and can avoid secondary pollution caused by the surfactants desorption, especially when the cationic polymers have been widely applied in wastewater treatment. As it is a novel class of adsorbent, the preparation of cationic polymer/bentonite and the adsorption properties for the removal of anionic and non-ionic organic pollutants from wastewater have been investigated by several researchers. ADDIN EN.CITE <EndNote><Cite><Author>Li</Author><Year>2009</Year><RecNum>1</RecNum><DisplayText>(Li, Yue et al. 2009)</DisplayText><record><rec-number>1</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427754″>1</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Li, Q.</author><author>Yue, Q. Y.</author><author>Su, Y.</author><author>Gao, B. Y.</author><author>Li, J.</author></authors></contributors><auth-address>School of Environmental Science and Engineering, Shandong University, Jinan, Shandong, PR China. [email protected]</auth-address><titles><title>Two-step kinetic study on the adsorption and desorption of reactive dyes at cationic polymer/bentonite</title><secondary-title>J Hazard Mater</secondary-title><alt-title>Journal of hazardous materials</alt-title></titles><periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></periodical><alt-periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></alt-periodical><pages>1170-8</pages><volume>165</volume><number>1-3</number><keywords><keyword>Adsorption</keyword><keyword>Azo Compounds/isolation &amp; purification</keyword><keyword>Bentonite/*chemistry</keyword><keyword>Cations</keyword><keyword>Coloring Agents/*isolation &amp; purification</keyword><keyword>Diffusion</keyword><keyword>Kinetics</keyword><keyword>Polymers/*chemistry</keyword><keyword>Sulfonamides/isolation &amp; purification</keyword><keyword>Thermodynamics</keyword></keywords><dates><year>2009</year><pub-dates><date>Jun 15</date></pub-dates></dates><isbn>1873-3336 (Electronic) 0304-3894 (Linking)</isbn><accession-num>19081187</accession-num><urls><related-urls><url>http://www.ncbi.nlm.nih.gov/pubmed/19081187</url></related-urls></urls><electronic-resource-num>10.1016/j.jhazmat.2008.10.110</electronic-resource-num></record></Cite></EndNote>(Li, Yue et al. 2009) For this application a novel cationic polymer will be synthesized from epichlorohydrin, ethylendiamine and sarcosine.
Epichlorohydrin is an organochlorine epoxide compound, is very reactive and hazardous. It is highly toxic, can be ignited under most ambient temperature conditions, Undergoes violent chemical change at elevated temperatures and pressures and is a primary skin irritant. With prolonged exposure to skin, the epichlorohydrin can be absorbed by the body and causes poisoning. Ethylendiamine is an organic compound that is a strongly basic amine and is very hazardous. Ethylenediamine readily reacts with moisture in humid air to produce a corrosive, toxic and irritating mist, to which even short exposures can cause serious damage to health. Epichlorohydrin and ethylene diamine are made non-toxic by sarcosine. Sarcosine is a produced as a by-product in glycine synthesis, is used in many clinical drugs and has no known toxicity.
Bentonite
Bentonite, which is a 2:1 type aluminosilicate, has been accepted as one of the appropriate low cost adsorbents to have the potential for removal of dyes from wastewater. Replacing the exchangeable inorganic cations (e.g. Na+, Ca2+, H+) on the internal and external surfaces of bentonite with organic cations such as quaternary ammonium salts, enhances the adsorption capacity as the bentonite surfaces change from hydrophilic to hydrophobic organophilic bentonite becomes an excellent adsorbent for organic pollutants and has been investigated for a wide variety of environmental applications. ADDIN EN.CITE <EndNote><Cite><Author>Li</Author><Year>2010</Year><RecNum>26</RecNum><DisplayText>(Li, Yue et al. 2010)</DisplayText><record><rec-number>26</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427879″>26</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Li, Qian</author><author>Yue, Qin-Yan</author><author>Su, Yuan</author><author>Gao, Bao-Yu</author><author>Sun, Hong-Jian</author></authors></contributors><titles><title>Equilibrium, thermodynamics and process design to minimize adsorbent amount for the adsorption of acid dyes onto cationic polymer-loaded bentonite</title><secondary-title>Chemical Engineering Journal</secondary-title></titles><periodical><full-title>Chemical Engineering Journal</full-title></periodical><pages>489-497</pages><volume>158</volume><number>3</number><dates><year>2010</year></dates><isbn>13858947</isbn><urls></urls><electronic-resource-num>10.1016/j.cej.2010.01.033</electronic-resource-num></record></Cite></EndNote>(Li, Yue et al. 2010)
Quaternary ammonium salts have been used most often to render bentonites hydrophobic. However, the main requirement for compounds to effect this change is that they comprise organic cations containing non-polar groups. Hence, it is worthwhile to broaden the range of compounds suitable for this purpose to enable alternative materials to be used for economic or other reasons. ADDIN EN.CITE <EndNote><Cite><Author>Li</Author><Year>2009</Year><RecNum>1</RecNum><DisplayText>(Li, Yue et al. 2009)</DisplayText><record><rec-number>1</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427754″>1</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Li, Q.</author><author>Yue, Q. Y.</author><author>Su, Y.</author><author>Gao, B. Y.</author><author>Li, J.</author></authors></contributors><auth-address>School of Environmental Science and Engineering, Shandong University, Jinan, Shandong, PR China. [email protected]</auth-address><titles><title>Two-step kinetic study on the adsorption and desorption of reactive dyes at cationic polymer/bentonite</title><secondary-title>J Hazard Mater</secondary-title><alt-title>Journal of hazardous materials</alt-title></titles><periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></periodical><alt-periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></alt-periodical><pages>1170-8</pages><volume>165</volume><number>1-3</number><keywords><keyword>Adsorption</keyword><keyword>Azo Compounds/isolation &amp; purification</keyword><keyword>Bentonite/*chemistry</keyword><keyword>Cations</keyword><keyword>Coloring Agents/*isolation &amp; purification</keyword><keyword>Diffusion</keyword><keyword>Kinetics</keyword><keyword>Polymers/*chemistry</keyword><keyword>Sulfonamides/isolation &amp; purification</keyword><keyword>Thermodynamics</keyword></keywords><dates><year>2009</year><pub-dates><date>Jun 15</date></pub-dates></dates><isbn>1873-3336 (Electronic) 0304-3894 (Linking)</isbn><accession-num>19081187</accession-num><urls><related-urls><url>http://www.ncbi.nlm.nih.gov/pubmed/19081187</url></related-urls></urls><electronic-resource-num>10.1016/j.jhazmat.2008.10.110</electronic-resource-num></record></Cite></EndNote>(Li, Yue et al. 2009)
Cationic Bentonite Polymer
Cationic polyelectrolytes fulfil the main requirements of materials that are suitable for rendering clays less polar and hence more hydrophobic. Some of them, in particular polyepicholorohydrin-sarcosine (SCP), will be used, as an adsorbent, in wastewater treatment. ADDIN EN.CITE <EndNote><Cite><Author>Yue</Author><Year>2007</Year><RecNum>33</RecNum><DisplayText>(Yue, Li et al. 2007)</DisplayText><record><rec-number>33</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427915″>33</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Yue, Q.</author><author>Li, Q.</author><author>Gao, B.</author><author>Wang, Y.</author></authors></contributors><titles><title>Kinetics of adsorption of disperse dyes by polyepicholorohydrin-dimethylamine cationic polymer/bentonite</title><secondary-title>Separation and Purification Technology</secondary-title></titles><periodical><full-title>Separation and Purification Technology</full-title></periodical><pages>279-290</pages><volume>54</volume><number>3</number><dates><year>2007</year></dates><isbn>13835866</isbn><urls></urls><electronic-resource-num>10.1016/j.seppur.2006.10.024</electronic-resource-num></record></Cite></EndNote>(Yue, Li et al. 2007) Recently, with the in-depth study of polymer/bentonite as adsorbent, several researchers begin to investigate the application of novel polymer/bentonite complexes for dye removal. Polyepicholorohydrin-Sarcosine (SCP), which is a new effective water-soluble cationic polyelectrolyte with amidocyanogen and ammonium ion, has the potential to render bentonite suitable for organic contaminants removal. The SCP was proved to be water soluble and was used to modify the bentonite. It has been indicated that –NH2 groups (which are also present in the SCP) are the main sites for the adsorption of dyes containing D-SO3? groups through ionic interactions of the coloured dye ions with the protonated amino groups on cationic bentonite polymer (CBP). The CBP used in order to remove dyes from effluents in adsorption systems, due to its high adsorption capacities and low-cost materials obtained from natural resources. ADDIN EN.CITE <EndNote><Cite><Author>Li</Author><Year>2009</Year><RecNum>1</RecNum><DisplayText>(Li, Yue et al. 2009)</DisplayText><record><rec-number>1</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427754″>1</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Li, Q.</author><author>Yue, Q. Y.</author><author>Su, Y.</author><author>Gao, B. Y.</author><author>Li, J.</author></authors></contributors><auth-address>School of Environmental Science and Engineering, Shandong University, Jinan, Shandong, PR China. [email protected]</auth-address><titles><title>Two-step kinetic study on the adsorption and desorption of reactive dyes at cationic polymer/bentonite</title><secondary-title>J Hazard Mater</secondary-title><alt-title>Journal of hazardous materials</alt-title></titles><periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></periodical><alt-periodical><full-title>J Hazard Mater</full-title><abbr-1>Journal of hazardous materials</abbr-1></alt-periodical><pages>1170-8</pages><volume>165</volume><number>1-3</number><keywords><keyword>Adsorption</keyword><keyword>Azo Compounds/isolation &amp; purification</keyword><keyword>Bentonite/*chemistry</keyword><keyword>Cations</keyword><keyword>Coloring Agents/*isolation &amp; purification</keyword><keyword>Diffusion</keyword><keyword>Kinetics</keyword><keyword>Polymers/*chemistry</keyword><keyword>Sulfonamides/isolation &amp; purification</keyword><keyword>Thermodynamics</keyword></keywords><dates><year>2009</year><pub-dates><date>Jun 15</date></pub-dates></dates><isbn>1873-3336 (Electronic) 0304-3894 (Linking)</isbn><accession-num>19081187</accession-num><urls><related-urls><url>http://www.ncbi.nlm.nih.gov/pubmed/19081187</url></related-urls></urls><electronic-resource-num>10.1016/j.jhazmat.2008.10.110</electronic-resource-num></record></Cite></EndNote>(Li, Yue et al. 2009)
Objectives
The objective of this study was to synthesize a novel non-toxic cationic polymer and characterize the cationic polymer using various techniques. The synthesized CP will then be modified with bentonite which will be tested as an adsorbent for the removal of dyes under different conditions, such as temperature, RPM, concentration of dyes and the amount of adsorbent used.

Experimental
Instrumentation
UV-vis (UV) spectra were recorded on a Varian Cary-50 UV spectrophotometer linked to a heating vessel temperature controlled cell holder (TCC -240A Shimadzu) in the range of 300 to 700nm. Deionized water was used as the reference/blank and quartz cuvettes were used for the analysis. It was used to show the adsorption of dye onto the bentonite polymer by measuring the absorption of the dye solutions at different times.

The 1H & 13C NMR spectra were recorded on Bruker (400 MHz) spectrophotometer in D2O, an internal reference. The chemical shifts were quoted in parts per million (ppm).

Fourier Transform Infra-Red Spectroscopy (FT-IR) experiments were conducted on a Varian 800 FT-IR spectrophotometer, the bond vibrations were measured at different wavelengths.
A Differential Light Scattering Malvern Zetasizer Nano ZS (Malvern Instruments Ltd, UK) Merck 2423 instrument was used to measure zeta potential, the charge that develops at the interface between a solid surface and its liquid medium is analysed by conducting zeta potential experiments. This was done using a U-tube quartz cuvette.
Chemicals
Epichlorohydrin, 1-Chloro-2,3-Epoxypropane, has a chemical formula of C3H5ClO with a molar mass 92.52 g/mol and a density of 1.18 g/mL. It is a colour liquid with an odour that resembles garlic and is soluble in water.
Sarcosine, N-methylglycine, has a chemical formula of C3H7NO2 with a molar mass of 83.09 g/mol and a density of 1.09 g/mL. It is in the form of a white powder that has no obvious odour.
Ethylenediamine, Ethane-1,2-diamine, has a chemical formula of C2H8N2 with a molar mass of 60.10 g/mol and a density of 0.90 g/mL. it is a colourless liquid with an ammonia like odour.
Sulphuric Acid, H2SO4, is a colourless and odourless liquid that is highly corrosive. It can cause severe burn with skin contact, at high concentrations.
Bentonite, is a clay mineral, which is mainly composed of montmorillonite (is a very soft phyllosilicate group of minerals that typically form in microscopic crystals, forming a clay).
The Three bi-functional reactive dyes used for the experimental procedure are reactive blue 222 (RB), reactive red 195 (RR) and reactive yellow 145 (RY) with molar masses of 1357.49 g/mol, 1136.32 g/mol and 1026.25 g/mol; respectively. The dyes are highly coloured and stains the skin, they are also carcinogenic. A combination of these three dyes, are commonly used in many dyeing process, in this instance they were used for a navy blue dyeing. RB has a chemical formula of C37H23ClN10Na6O22S7 and is navy blue powder. RR has a chemical formula of C31H19ClN7Na5O19S6 and occurs as blue powder. RY occurs as a red powder and has a chemical formula of C28H20ClN9Na4O16S5.
Synthesis of Cationic Polymer
22.5 g of epichlorohydrin was added to a three necked round bottom flask and it was left to stir at 30º C in an oil bath that was placed on a hot plate. 3.5 g of sarcosine was dissolved in 40.0 g of deionized water and to the stirring epichlorohydrin. This was left to stir at 30º C for 3 hours. After 3 hours, 15.5 g of ethylenediamine was added carefully using a separating funnel. The temperature was then set to 70º C and the reagents were left to stir for 1 hour. 7.5 g of epichlorohydrin was added using a separating funnel. The reaction was left to proceed for 19 hours. Approximately ±1 mL of H2SO4 was added drop-wise over 3hours. The reaction was taken off the heat and left to cool for 30 minutes. The epichlorohydrin-sarcosine was precipitated with acetone. The acetone and polymer was stirred with a stirring rod until still and the acetone was then decanted. The polymer was the solidified with DMF and was stirred vigorously. The DMF was then decanted. The polymer was then placed in the oven at ±100º C for 48 hours.

Modification with Bentonite
Bentonite was placed in the oven at approximately ±100º C for 18 hours. 12 g of bentonite was weighed into a 500 mL beaker and 100 g of deionized water was added. This was left to stir on a hot plate at 70º C for 30 minutes. 3 g of SCP was weighed and dissolved in 100mL of deionized water, to make 3% of CP solution. The 3% SCP solution was slowly added to the bentonite. This was left to stir for 24 hours. The mixture was removed from the heat and left to cool for 30 minutes. The modified bentonite was then filtered and placed in the oven for 24 hours. Once dry, the precipitate was left to cool, then ground into fine particles with a mortar and pestle.

UV Calibration
100 mL of 50 ppm RB standard, RR standard, RY standard and a mixed dye standard were prepared and analysed on UV spectroscopy to obtain the ?max of each dye. 100mL of 10 ppm, 30 ppm, 50 ppm, 70 ppm and 90 ppm mixed dye standards were prepared with deionized water and were analysed by UV spectroscopy. The absorbances were recorded at the ?max obtained and linear regression graphs were plotted.
Adsorption
Kinetic studies on the adsorption of the bi-functional reactive dyes onto the CBP were carried out on the mixed dye solution, except for experiments where each dye solution was analysed.
The dye concentration was 30 mg/L, except for and leading up to the experiment involving the analysis of different dye concentrations. The pH of the mixed dye solution remained unchanged for all the experiments except for those concerning pH. The pH was changed with 0.1 mol/L HCl or 0.1mol/L NaOH, using a pH meter. A definite amount of 0.15 g of CBP was added to 250 mL conical flasks with 100mL of dye solution. The time was measured with a timer while shaking in the horizontal shaker. The temperature was kept constant at 30º C and the speed was set at 150 RPM. 5 mL of sample was taken every 10 minutes for 120 minutes and was centrifuged at 3500 RPM for 2 minutes, to separate the supernatant and the adsorbents. The absorbance measurements were recorded at the maximum wavelengths corresponding to each dye. The reproducibility was ensured by conducting the analysis in triplicate.

Equations
The percentage of dye adsorbed on to the CBP was recorded as follows:
%DR = A0-AA0 x 100 (1)
A0 = Initial absorbance of the dye
A= Absorbance of dye at time (t)
The amount of dye adsorbed, Qt (mg/g) was also recorded at different times (t), was calculated as follows:
Qt = V(C0-Ct)W (2)
C0 = Initial concentrations (mg/L) of dye
Ct = Concentrations (mg/L) of dye in the solution at time t
V = Volume (L) of the dye solution
W = Weight (g) of the CBP adsorbent
Pseudo first-order rate equation:
lnA = -k1t + lnAo (3)
A = Concentration (mg/L) of dye at time (t)
Ao = Initial concentration (mg/L) of dye/ Constant
k1 = Rate constant
t = Time (min)
Pseudo second-order rate equation:
1A = k2t + 1A0 (4)
A = Concentration (mg/L) of dye at time (t)
Ao = Initial concentration (mg/L) of dye/ constant
k2 = Rate constant
t = Time (min)
The data was then fitted into the Intraparticle Diffusion Model (using the Weber-Morris model):
Qt = kintt1/2 + C (5)
Qt = Amount of dye adsorbed (mg/g)
Kint = intraparticle diffusion rate constant (mg/g?min1/2)
C = Constant.
Langmuir isotherm model:
PV = PV? + 1kLV? (6)
P = concentration (mg/L)
V = Volume (L) of dye solution
kL = Constant
V? = Constant
Freundlich isotherm model:
ln V = ln C1 + 1C2 lnP (7)

V = volume (L) of the adsorbate adsorbed over Volume (L) of adsorbate corresponding to complete monolayer coverage.
C1 = Constant
C2 = Constant
To find the effect of temperature on reaction velocity, the Arrhenius equation was applied:
lnk2 = lnA – Ea/RT (8)
A = pre-exponential factor
Ea = Activation Energy of the reaction
To find the Enthalpy and Entropy of the reaction, the following equation was applied:
lnkL = ?SRT – ?HR (9)
k = rate constant
?S = Entropy
R = constant (8.314)
T = Temperature
?H = Enthalpy
To find the Gibbs Free Energy, the following (Van Hofft) equation was applied:
?G = -RT lnk (10)
?G = Gibbs Free EnergyR = constant
T = Temperature
k = Langmuir constant
**The constants in eq. 3-8 were obtained from the linear regression line equations.
Results and Discussion
Synthesis of SCP
SCP is a water soluble novel cationic polymer, it is brown toffee in colour and is very viscous. Solidifies at 105ºC, if spread across a surface but melts once more at room temperature. The SCP also dissolves in more polar organic solvents such as methanol and DMSO. SCP solidifies with THF, acetone and DMF, which means that either solvent can be used to either precipitate or solidify the SCP. A grey greasy like substance is formed when the acetonitrile or ethyl acetate is added to the SCP. When added to chloroform, the SCP is insoluble and forms a layer on the top of the chloroform solvent.

Figure 2: Synthesis of SCP
Modification with Bentonite
Visually, the characteristics of CBP do not appear to differ from bentonite. When filtered and dried, the CBP was set in layers.

Figure 3: Modification of CP with Bentonite to produce CBP
Characterization
NMR
At 4 – 4.25 ppm, the proton from O-H is shown, at ±3.5 ppm the protons present in CH2 are shown and the peaks present at 2.3 – 3.5 ppm show CH and CH3 aliphatic protons.

Figure 4: 1H NMR spectrum for SCP
Zeta-Potential
Zeta potential on the SCP, showed a positive value of 3.54 mV, which means that the SCP particles have no force that prevents the particles coming together and flocculating.

Figure 5: Zeta Potential for SCP
FT-IR
For CP – At 3345.02 cm-1, the N-H stretch of the SCP is represented as a long peak. H-C is a peak coming out of the shoulder of the N-H stretch, and occurs at 2840.47 cm-1 as small peaks. The C=O bands appear at 1622.99 cm-1 as a sharp narrow peak. At 1455.53 cm-1, C-N bend is shown as a sharp peak and the last band is at 1062.88 cm-1 which is the C-O stretch.

For bentonite and CBP, the FT-IR spectrums are the same. The FT-IR spectrum show a broad band at 3391.83 cm-1 which shows the O-H groups present in the water molecules in the bentonite as well as the CBP. The water molecules are also shown at 1738.87 cm-1, as a small sharp peak. The Si-O stretch is shown at 1365.88 cm-1 and 1027.06 cm-1 as small and long narrow peaks; respectively. At 999.66 cm-1, the Al-Al-OH peak is shown as a small sharp peak and the Al-O-Si and Si-O-Si in plane vibrations are shown at 694.23 cm-1, the peak show is very small.

Figure 6: FT-IR Spectrum of SCP, Bentonite and CBP
?max Determination
Single standards were analysed on the UV to obtain ?max for each dye, it was found that RB, RR and RY had a ?max of 614.5nm, 539.5nm and 413.0nm; respectively. A mixed standard, containing RB, RR and RY was also analysed, the ?max found were 612.5nm, 547.0nm and 402.0nm; respectively. The ?max shifts are shown in fig. 16. The auxochromes in the mixed standard interact and mix, this is seen by purple colour of the mixed dye standard. RB undergoes a blue shift in which the ?max decreases by 2nm, RR undergoes a bathochromic (red) shift in which its ?max increases by 7.5nm and RY undergoes a blue shift where the ?max decreases by 11nm.

Figure 7: (a) UV spectrum of the mixed dye standard, RB, RR and RY.

UV Calibration
Mixed standards ranging from 10 ppm to 90 ppm were analysed by UV spectroscopy. Three absorbance values were recorded at the obtained ?max for RB, RR and RY; respectively. The linear regression line equations were obtained and shown in fig. 16. The linear regression equation for each dye was used to calculate the concentrations (Ct), by substituting the absorption values obtained, as y.

Figure 8: Calibration curves of RB, RR and RY
Adsorption
One of the biggest challenges in adsorption studies is the interpretation of the adsorption mechanism. The adsorption mechanism is dependent on the chemical composition of the adsorbent, the environment in which the solution is in, the nature of the adsorbent, the nature of the adsorbate and the type of interactions occurring between the adsorbent and adsorbate. ADDIN EN.CITE <EndNote><Cite><Author>A</Author><Year>2011</Year><RecNum>167</RecNum><DisplayText>(A 2011)</DisplayText><record><rec-number>167</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1415530523″>167</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Salem M A</author></authors></contributors><titles><title>the role of polyaniline salts in the reomval of direct blue 78 from aqeous solution: A Kinectic study</title><secondary-title>Reactive and Functional Polymers</secondary-title></titles><periodical><full-title>Reactive and Functional Polymers</full-title></periodical><pages>707-714</pages><volume>70</volume><dates><year>2011</year></dates><urls></urls></record></Cite></EndNote>(A 2011) The adsorption of the dye should occur in the following proposed steps:
In aqueous solutions, the dye molecule rapidly dissolves and the sulphonate group (present in the dye) is dissociated and is converted into dye anions:-
(Dye)-SO3Na + H2O(aq) (Dye)-SO3- + Na+
In the presence of the Hydrogen ions H+, the amino groups present of the SCP were protonated as (NH3+).

The anions present in the reactive dyes migrate from the solution to the surface of the CBP particles.

The dye anions are electrostatically attracted by the nitrogen moiety present in the SCP.

(CBP)-NH3+ + (Dye)-SO3- (CBP)-NH3+-O3-S-(Dye)
Therefore, adsorption of the dye molecules onto the surface of CBP occurs by chemisorption. ADDIN EN.CITE <EndNote><Cite><Author>Janaki</Author><Year>2012</Year><RecNum>7</RecNum><DisplayText>(Janaki, Oh et al. 2012)</DisplayText><record><rec-number>7</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427782″>7</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Janaki, V.</author><author>Oh, Byung-Taek</author><author>Vijayaraghavan, K.</author><author>Kim, Jin-Won</author><author>Kim, Seol Ah</author><author>Ramasamy, A. K.</author><author>Kamala-Kannan, Seralathan</author></authors></contributors><titles><title>Application of bacterial extracellular polysaccharides/polyaniline composite for the treatment of Remazol effluent</title><secondary-title>Carbohydrate Polymers</secondary-title></titles><periodical><full-title>Carbohydrate Polymers</full-title></periodical><pages>1002-1008</pages><volume>88</volume><number>3</number><dates><year>2012</year></dates><isbn>01448617</isbn><urls></urls><electronic-resource-num>10.1016/j.carbpol.2012.01.045</electronic-resource-num></record></Cite></EndNote>(Janaki, Oh et al. 2012)
The experiments were conducted in triplicate and a place was used for each experimental parameter. UV analysis was conducted with a wavelength range from 700 nm to 300 nm, on 5 mL samples extracted every 10 minutes for 2 hours. The samples were centrifuged for 2 minutes at a stirring rate of 3500 RPM.

Adsorption characteristics
Different adsorbents
The SCP, Bentonite and the CBP were tested for their adsorption capacities on 50 ppm mixed dye solution. This was done to analyse the efficiency of the CBP against its reactants and to test if adsorption would occur using the reactants, alone. As shown in fig.9 the dye was quickly adsorbed onto the CBP, while the SCP dissolved in the mixed dye solution and results obtained for the bentonite was erratic but adsorption did not occur. The bentonite remained as a suspension in the dye solution, making the solution appear cloudy.

Figure 9: Plots of %DR vs. Time (min) for (a) RB; (b) RR and (c) RY
Different dye solutions
50 ppm single dye standards were analysed and the rate of adsorption was compared to that of a 50 ppm mixed dye standard (MDS). It was found that the single standards adsorb faster than that of the mixed dye standard, this is because the dye particles don’t have to compete with each other, in the single standards for adsorption sites. This experiment was conducted at 30ºC, 150 RPM, pH 5.5 and with 0.15 g of CBP.

Figure 10: % DR vs. Time (min) for RB, RR, RY and a mixed dye standard
Change in initial dye concentrations
It was observed that Qt and %DR, for each dye increases with an increase in time until it reaches the end of the adsorption process. Qt and %DR are observed to increase rapidly at the start of the adsorption process and to thereafter increase slowly until the end of the adsorption process. This is due the lower number of adsorption sites available as time increases. Since the 10 ppm dye adsorbs at a very fast rate and the 50 ppm dye solution adsorbs very slowly, the 30 ppm dye solution was selected as the optimum parameter.

Figure 11:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of RB onto CBP at different initial concentrations, T=30ºC, pH 5.5

Figure 12:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of RR onto CBP at different initial concentrations, T=30ºC, pH 5.5

Figure 13:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of RY onto CBP at different initial concentrations, T=30ºC, pH 5.5

Change in mass of CBP (adsorbent)
The effect of adsorbent amount (dosage) on the adsorption was investigated for the adsorption of a mixed dye solution (100 mL) with an initial concentration 30 ppm at pH of 5.5. The percentage removal of dye increased with increasing the adsorbent amount, as evident. This is due to increase in adsorbent sites for the adsorption of dye with increased adsorbent dosage. Even though the percentage of dye removal increased with adsorbent dosage, the adsorption capacity (mg of dye adsorbed/g of adsorbent) increased with decrease in adsorbent dosage. This is because the amount of dye in contact with unit weight of adsorbent increases with decrease in adsorbent dosage.

However, with increasing adsorbent load, the quantity of dye adsorbed onto the unit weight of the adsorbent cuts down as can be seen from the declining curve of Qt. This may be attributed to the overlapping or aggregation of adsorption sites, which leads to a decrease in total available adsorbent surface area and an increase in diffusion path length. From this experimental procedure, it was determined that 0.20 g CBP was the optimum parameter but 0.15 g was selected, since full adsorption had occurred in the time frame and it is more cost effective.

Figure 14:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of 30ppm RB onto different masses of adsorbent, CBP, T=30ºC, pH 5.5

Figure 15:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of 30ppm RR onto different masses of adsorbent, CBP, T=30ºC, pH 5.5

Figure 16:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of 30ppm RY onto different masses of adsorbent, CBP, T=30ºC, pH 5.5
Change in pH of the dye solutions
The increased adsorption and initial adsorption rate decreased with decreasing pH. At pH=2, the Amino groups of the dye are protonated, so that positive (NH2+) and negative (OSO3?) groups were present which interacted with negative surface charges of the acidic clay mineral and cationic groups of CBP. At low pH values, the dye bears strong negative charge due to the increases of the protonation of ?SO3? groups, thereby a significantly high electrostatic attraction existing between the positively charged adsorption sites and the negatively charged dyes and result in the significantly enhanced reactive dye anions adsorption.

At pH=7, the dye molecules were only negatively charged, and only CBP played a major role in adsorption, which reduced the amount of dye adsorbed. At higher pH, OH? competed with the anionic dye molecules and reduced the adsorption on CBP.
As the pH of the system increases, besides the decreases of negative charge of reactive dye, the positive charge of adsorbent surface also decrease due to the abundance of OH? and consequently becomes negatively charged in higher pHs, which can weaken the reaction of dye and CBP and as a result both the adsorption amount and adsorption rate decrease. And at strong alkaline pH (pH 11), due to the ionic repulsion exit between the negatively charged surface and the anionic dye molecules and no exchangeable anions exit on the outer surface of the adsorbent, the adsorption capacities for reactive dyes of CBP decrease significantly. ADDIN EN.CITE ;EndNote;;Cite;;Author;Li;/Author;;Year;2009;/Year;;RecNum;1;/RecNum;;DisplayText;(Li, Yue et al. 2009);/DisplayText;;record;;rec-number;1;/rec-number;;foreign-keys;;key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427754″;1;/key;;key app=”ENWeb” db-id=””;0;/key;;/foreign-keys;;ref-type name=”Journal Article”;17;/ref-type;;contributors;;authors;;author;Li, Q.;/author;;author;Yue, Q. Y.;/author;;author;Su, Y.;/author;;author;Gao, B. Y.;/author;;author;Li, J.;/author;;/authors;;/contributors;;auth-address;School of Environmental Science and Engineering, Shandong University, Jinan, Shandong, PR China. [email protected];/auth-address;;titles;;title;Two-step kinetic study on the adsorption and desorption of reactive dyes at cationic polymer/bentonite;/title;;secondary-title;J Hazard Mater;/secondary-title;;alt-title;Journal of hazardous materials;/alt-title;;/titles;;periodical;;full-title;J Hazard Mater;/full-title;;abbr-1;Journal of hazardous materials;/abbr-1;;/periodical;;alt-periodical;;full-title;J Hazard Mater;/full-title;;abbr-1;Journal of hazardous materials;/abbr-1;;/alt-periodical;;pages;1170-8;/pages;;volume;165;/volume;;number;1-3;/number;;keywords;;keyword;Adsorption;/keyword;;keyword;Azo Compounds/isolation ;amp; purification;/keyword;;keyword;Bentonite/*chemistry</keyword><keyword>Cations</keyword><keyword>Coloring Agents/*isolation &amp; purification</keyword><keyword>Diffusion</keyword><keyword>Kinetics</keyword><keyword>Polymers/*chemistry</keyword><keyword>Sulfonamides/isolation &amp; purification</keyword><keyword>Thermodynamics</keyword></keywords><dates><year>2009</year><pub-dates><date>Jun 15</date></pub-dates></dates><isbn>1873-3336 (Electronic) 0304-3894 (Linking)</isbn><accession-num>19081187</accession-num><urls><related-urls><url>http://www.ncbi.nlm.nih.gov/pubmed/19081187</url></related-urls></urls><electronic-resource-num>10.1016/j.jhazmat.2008.10.110</electronic-resource-num></record></Cite></EndNote>(Li, Yue et al. 2009) ADDIN EN.CITE <EndNote><Cite><Author>Yue</Author><Year>2007</Year><RecNum>33</RecNum><DisplayText>(Yue, Li et al. 2007)</DisplayText><record><rec-number>33</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1400427915″>33</key><key app=”ENWeb” db-id=””>0</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Yue, Q.</author><author>Li, Q.</author><author>Gao, B.</author><author>Wang, Y.</author></authors></contributors><titles><title>Kinetics of adsorption of disperse dyes by polyepicholorohydrin-dimethylamine cationic polymer/bentonite</title><secondary-title>Separation and Purification Technology</secondary-title></titles><periodical><full-title>Separation and Purification Technology</full-title></periodical><pages>279-290</pages><volume>54</volume><number>3</number><dates><year>2007</year></dates><isbn>13835866</isbn><urls></urls><electronic-resource-num>10.1016/j.seppur.2006.10.024</electronic-resource-num></record></Cite></EndNote>(Yue, Li et al. 2007) ADDIN EN.CITE <EndNote><Cite><Author>Zohra</Author><Year>2008</Year><RecNum>91</RecNum><DisplayText>(Zohra, Aicha et al. 2008)</DisplayText><record><rec-number>91</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1405352806″>91</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Zohra, Bouberka</author><author>Aicha, Khenifi</author><author>Fatima, Sekrane</author><author>Nourredine, Bettahar</author><author>Zoubir, Derriche</author></authors></contributors><titles><title>Adsorption of Direct Red 2 on bentonite modified by cetyltrimethylammonium bromide</title><secondary-title>Chemical Engineering Journal</secondary-title></titles><periodical><full-title>Chemical Engineering Journal</full-title></periodical><pages>295-305</pages><volume>136</volume><number>2</number><keywords><keyword>Benzopurpurin 4B</keyword><keyword>Isotherm</keyword><keyword>Organophilic clay</keyword><keyword>Kinetics</keyword><keyword>Thermodynamic</keyword><keyword>Pseudo-second order sorption kinetics</keyword></keywords><dates><year>2008</year></dates><publisher>Elsevier B.V</publisher><isbn>1385-8947</isbn><urls><related-urls><url>http://dut.summon.serialssolutions.com/2.0.0/link/0/eLvHCXMwTV1LCgIxDC3iCQTF5Vyg0HSmNVmLo4hLh8Fl2qRL7780FRceILzd-0B4z7mhBWQMFqaN6SYIXMOovbY81TYxfh9o1mVaH_S6x-sfm887t9H33i3z5Xm–d8YgK9mgdGfSBRaBjP4FCGrKauMhtIlCqT05WQQ7GUohUJLlDQrqEYpMbFShoPbWqDWoxty5rHvJoL0KyZsDNgsJcYixhv1A3KQLS4</url><url>http://www.sciencedirect.com/science/article/pii/S1385894707002458</url></related-urls></urls><electronic-resource-num>10.1016/j.cej.2007.03.086</electronic-resource-num></record></Cite></EndNote>(Zohra, Aicha et al. 2008)
The optimum pH was a pH of but a pH of 5.5 could also be used, this would save chemical cost in the neutralisation step of the effluent treatment process. A pH of 7 and up cannot be used, as it is ineffective.

Figure 17:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of 30ppm RB onto 0.15 g of CBP, T=30ºC, at different pH

Figure 18:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of 30ppm RR onto 0.15 g of CBP, T=30ºC, at different pH

Figure 19:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of 30ppm RY onto 0.15 g of CBP, T=30ºC, at different pH
Change in RPM
As shown in the Qt vs. Time (min) and the %DR vs. Time (min) graphs, the rate of adsorption increases significantly with an increase in stirring rate. An example of this trend shows that complete adsorption occurs in the first 20 minutes for a stirring rate of 200 RPM, as compared to a stirring rate of 100 RPM which complete adsorption of RB only occurs after 80 minutes. From these results, it was determined that the optimum stirring rate was 200 RPM.

Figure 20:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of 30ppm RB onto 0.15 g of CBP, T=30ºC, pH5.5, at different RPM

Figure 21:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of 30ppm RR onto 0.15 g of CBP, T=30ºC, pH5.5, at different RPM

Figure 22:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of 30ppm RY onto 0.15 g of CBP, T=30ºC, pH5.5, at different RPM
Change in Temperature
The Qt vs. Time (min) and %DR vs. Time (min) graphs vary for each dye varies with the changes in temperature. The results show that RB adsorbs faster on CBP as the temperature was increased. The Qt vs. Time (min) and %DR vs. Time (min) graphs for RR show that temperate is not a big factor in the adsorption of the RR dye particles onto CBP. These results also reflect that at the start of the adsorption process is temperature is not a factor for RY but toward the end of the adsorption process RY adsorbs faster at 30ºC.

Figure 23:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of 30ppm RB onto 0.15 g of CBP, RPM = 150, pH5.5, at different temperatures

Figure 24:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of 30ppm RR onto 0.15 g of CBP, RPM = 150, pH5.5, at different temperatures

Figure 25:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of 30ppm RY onto 0.15 g of CBP, RPM = 150, pH5.5, at different temperatures
Effluent
As expected RB adsorbs faster than RR and RY. The effluent was at a pH of 10.9 but the adsorption process was not successful without acidifying the effluent first. An experiment was conducted on the effluent after neutralization but was also unsuccessful. The effluent had to be acidified to a pH of 5.5 to allow adsorption to occur. The acidification occurred after a test was done on the original 10% effluent and a neutralised 10% effluent, showed that no adsorption occurred.

Figure 26:(a) relationship of %DR vs. time(min)and (b) relationship of Qt vs. time (min) for the adsorption of 10% dye effluent onto 0.15 g of CBP, RPM = 150, pH5.5, at T = 30ºC
Adsorption Kinetics
To evaluate the kinetic mechanism that controls the adsorption process , the pseudo first-order and pseudo second-order were used to interpret the experimental data. The r2 values for both orders were calculated and compared. It is clear by the correlation co-efficients , that the reaction follows pseudo second-order chemical reaction and that this is noteworthy in the rate-controlling step. The adsorption kinetics of surfactants at solid-liquid interfaces, which are generally found to possess two-steps with two-rate constants k1 and k2.

Change in Initial Dye Concentrations
The adsorption kinetics of RB, RR and RY from solution onto CBP at different concentrations were simulated by the pseudo first-order and pseudo second order models. The rate constants k1 and k2 were obtained and compared to each other. The correlation co-efficients obtained were better (closer to 1) for the pseudo second order graphs than the pseudo first order graphs.
The values for k1 increase for RB with an increase in initial dye concentration, but this trend is not followed by RR and RY. The values for k2 decreased with the increase of initial dye concentration for all three dyes. It is proposed that the adsorption rate at any instant would be proportional to the difference between the initial amount of the adsorbed dye and the dye concentration in the solution, at any time t. Due to the solute transfer from the bulk to the surface-bound phase, the local concentration of dye significantly increases. Dye initial concentration increasing is favourable to dye molecule transference so that values of k1 increase with A0.
It is noted that magnitude of k2 in most cases is smaller than k1. For the kinetics of Bi-functional reactive dyes adsorption at solid–liquid interfaces, the process was found to possess two steps with two rate constants k1 and k2.

Theoretically, in the case of adsorption of reactive dyes on CBP interfaces, after some initial progress of adsorption with time, the crowded dye molecules on the surface of bentonite tend to adsorb onto available activation sites to form adsorbed patches of surface, which may result in the creation of more vacant spaces for further adsorption of reactive dye from the bulk to the surface. And as a result, the second adsorption step with adsorption rate k2 takes place, but compared with the first process, the second one is relatively slow. ADDIN EN.CITE <EndNote><Cite><Author>Khenifi</Author><Year>2007</Year><RecNum>90</RecNum><DisplayText>(Khenifi, Bouberka et al. 2007)</DisplayText><record><rec-number>90</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1405352806″>90</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Khenifi, A.</author><author>Bouberka, Z.</author><author>Sekrane, F.</author><author>Kameche, M.</author><author>Derriche, Z.</author></authors></contributors><titles><title>Adsorption study of an industrial dye by an organic clay</title><secondary-title>Adsorption</secondary-title></titles><periodical><full-title>Adsorption</full-title></periodical><pages>149-158</pages><volume>13</volume><number>2</number><keywords><keyword>CTAB</keyword><keyword>Chemistry</keyword><keyword>Industrial Chemistry/Chemical Engineering</keyword><keyword>Langmuir</keyword><keyword>Surfaces and Interfaces, Thin Films</keyword><keyword>Adsorption</keyword><keyword>Engineering Thermodynamics, Transport Phenomena</keyword><keyword>Bentonite</keyword><keyword>Supranol Yellow 4GL</keyword></keywords><dates><year>2007</year></dates><pub-location>Boston</pub-location><publisher>Springer US</publisher><isbn>0929-5607</isbn><urls><related-urls><url>http://dut.summon.serialssolutions.com/2.0.0/link/0/eLvHCXMwTZ0xDsIwDEUjxAmQQIy9QCSncdNkRhSEGKkqRsexx95_xEUMnMBe_P2-ZH071ylkymBm2pQOAxBDlC22fGBFyt8DmmXG5Vnej_72p-bTwe1kPbp5ur4ud_97BuDZPMDoMYH2ibIY4RZOJBrSlnU1AtqEUmBqxvocinKNLLYWg1Qcaos278244OT2Zqjl7Lq-RYOeppKVUBplFRCO1boEsAof-sAv5w</url><url>http://link.springer.com/article/10.1007%2Fs10450-007-9016-6</url></related-urls></urls><electronic-resource-num>10.1007/s10450-007-9016-6</electronic-resource-num></record></Cite></EndNote>(Khenifi, Bouberka et al. 2007) PEVuZE5vdGU+PENpdGU+PEF1dGhvcj5MaTwvQXV0aG9yPjxZZWFyPjIwMDk8L1llYXI+PFJlY051
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ADDIN EN.CITE.DATA (Zohra, Aicha et al. 2008, Li, Yue et al. 2009)
Due to the different structures of dyes, which can affect both the reset of adsorbed dyes and the re-adsorption of dyes in solution and consequently has influence on the second adsorption step rate, the value of k2 could present some different trend compared with that of k1, especially in different solution concentrations.
Name of Dye Concentration Rate 1 Rate 2
k1 lnA0 A0 r2 k2 1AoA0 r2
RB 10 mg/L 0.0026 3.8081 45.06 0.9947 0.0082 0.1639 6.101281 1
30 mg/L 0.0048 2.6963 14.82 0.8975 0.0009 0.051 19.60784 0.9533
50 mg/L 0.0044 2.5285 12.53 0.8206 0.00006 0.0264 37.87879 0.9002
RR 10 mg/L 0.0115 1.7069 5.51 0.9795 0.0132 0.1039 9.624639 0.956
30 mg/L 0.0048 2.6672 14.4 0.8822 0.0007 0.0516 19.37984 0.9962
50 mg/L 0.0035 2.5977 13.43 0.8153 0.00005 0.00005 20000 0.808
RY 10 mg/L 0.0252 1.7993 6.04 1 – –  – –
30 mg/L 0.0039 2.7954 16.37 0.8748 0.0009 0.0627 15.94896 0.9935
50 mg/L 0.0035 2.7858 16.21 0.8196 0.00009 0.0286 34.96503 0.7432
Table 1: summary of results from regression line equation from the linear of plot of lnA vs. Time (min), pseudo first-order reaction equation and from the linear of plot of 1A} vs. Time (min), pseudo second-order reaction equation for different initial dye concentrations
Change in mass of CBP (adsorbent)
The pseudo first-order model assumes that adsorption occurs due to a difference in concentration between the surface of the adsorbate and the dye solution. The pseudo second-order model occurs due to the saturation of adsorption sites on the surface. The good fit of the results in the pseudo second-order model suggests that that the adsorption process is of a chemical nature. The rate constants, k1 and k2 increase with an increase of mass of CBP for all the dyes. The correlation co-efficient are better for the pseudo second-order model, which shows that the results fit better to the pseudo second-order model.
Name of Dye Mass of CBP Rate 1 Rate 2
k1 lnA0 A0 r2 k2 1AoA0 r2
RB 0.10 g 0.0108 2.5955 13.4 0.931 0.0016 0.05 20 0.9836
0.15 g 0.011 0.7494 2.12 0.9684 0.0021 0.0578 17.30104 0.9903
0.20 g 0.011 3.1816 24.16 1 0.0006 0.0333 30.03003 1
RR 0.10 g 0.005 2.7076 14.99 0.8924 0.0015 0.0367 27.24796 0.9564
0.15 g 0.0056 2.8096 16.6 0.9235 0.0029 0.022 45.45455 0.9607
0.20 g 0.0087 3.0096 20.28 0.9252 77.507 2.5981 0.384897 0.9759
RY 0.10 g 0.0038 2.8648 17.55 0.9117 0.0017 0.0313 31.94888 0.9769
0.15 g 0.0066 2.8416 17.14 0.9521 0.002 0.0605 16.52893 0.9976
0.20 g 0.0143 2.0621 7.86 0.9816 0.0073 0.0624 16.02564 1
Table 2: summary of results from regression line equation from the linear of plot of lnA vs. Time (min), pseudo first-order reaction equation and from the linear of plot of 1A} vs. Time (min), pseudo second-order reaction equation for different masses of adsorbent
Change in pH of dye solutions
The pH value of the solution, which affects the surface charge of the adsorbent and the degree of speciation of adsorbate, was an important controlling parameter in the adsorption process. The pH dependence of adsorption was studied with a constant initial dye concentration of 30 mg/L and 1.5 g/L of CBP at various initial pH values. The correlation coefficients, r2, the two-step kinetic rate parameters, k1 and k2 are also shown in Tables 5-6.
The rate constants, k1 and k2 decrease with an increase in pH, showing that adsorption occurs faster at a lower pH than a higher pH. The correlation co-efficient are much better for the pseudo second-order model than the pseudo first-order model. The correlation co-efficient for the alkaline pH was very low and can be attributed to the lack of adsorption.
Name of Dye pH Rate 1 Rate 2
k1 lnA0 A0 r2 k2 1AoA0 r2
RB 2 0.0072 2.8996 18.17 0.8182 0.0065 0.0533 18.76173 0.9494
5.5 0.0048 2.6963 14.82 0.8972 0.0008 0.0584 17.12329 0.9868
7 0.003 2.6478 14.12 0.8015 0.0003 0.0616 16.23377 0.9233
11 – – –  – – – –  –
RR 2 0.006 2.9373 18.86 0.8732 0.006 0.0468 21.36752 0.9329
5.5 0.0048 2.6672 14.4 0.8822 0.0007 0.0523 19.12046 0.9959
7 0.0039 2.5481 12.78 0.8692 0.0003 0.055 18.18182 0.981
11 0.0019 0.6772 1.97 0.1753 0.000005 0.0358 27.93296 0.2077
RY 2 0.0069 2.9412 18.94 0.9519 0.0091 0.0285 35.08772 0.8918
5.5 0.0039 2.7954 16.37 0.8748 0.0009 0.0627 15.94896 0.9935
7 0.0031 2.7289 15.32 0.8514 0.0004 0.0645 15.50388 0.9685
11 0.0011 0.9063 2.48 0.2844 0.000004 0.0363 27.54821 0.4515
Table 3: summary of results from regression line equation from the linear of plot of lnA vs. Time (min), pseudo first-order reaction equation and from the linear of plot of 1A} vs. Time (min), pseudo second-order reaction equation for different pH
Change in RPM
As shown in Table 4 adsorption occurs at a very high rate for RB, occurring in the first 10 minutes of the adsorption process which made it difficult to establish the pseudo second-order kinetics for 200 RPM. The values for k2 were lower than the values for k1. The k1 values for RR decreased from 100 RPM to 150 RPM but then increased from 150 RPM to 200 RPM, which were inconsistent in comparison to k2, which increased consistently with an increase in stirring rate.
Both k1 and k2 increased consistently with an increase in stirring rate for RY. For RB k1 decreased from 100 RPM to 150 RPM but k2 increase from 100 RPM to 150 RPM.

Name of Dye RPM Rate 1 Rate 2
k1 lnA0 A0 r2 k2 1AoA0 r2
RB 100 0.0118 2.3944 10.96 0.9593 0.0008 0.0482 20.74689 0.9753
150 0.011 2.7494 16.63 0.9684 0.0021 0.0578 17.30104 0.9903
200 0.0483 2.4356 11.42 1  – –  –   –
RR 100 0.0076 2.4259 11.31 0.9629 0.0017 0.0092 108.6957 0.9023
150 0.0056 2.8096 16.6 0.935 0.0029 0.0022 454.5455 0.9607
200 0.0062 2.8612 17.48 0.9673 0.0047 0.011 90.90909 0.8674
RY 100 0.0064 2.5866 13.28 0.9868 0.0014 0.0319 31.34796 0.9504
150 0.0066 2.8416 17.14 0.9521 0.0019 0.063 15.87302 0.9943
200 0.0068 2.9151 18.45 0.9648 0.0024 0.0701 14.26534 0.9834
Table 4: summary of results from regression line equation from the linear of plot of lnA vs. Time (min), pseudo first-order reaction equation and from the linear of plot of 1A} vs. Time (min), pseudo second-order reaction equation for different RPM
Change in Temperature
It can be found that the values of k1 increase from 30ºC to 40ºC but there is no change from 40ºC to 50ºC. RB adsorbs very fast onto the CBP at 40ºC and 50ºC, occurring in the first 10 minutes which made it difficult to fit into a kinetic model and therefore k1 and k2 could not be determined. The kinetic rate constant, k2 increase with temperature for RR and RY. This can be attributed to the rise of temperature accelerating the transference of the dye molecules from the bulk solution to the CBP, which resulted in a faster uptake of dye.
Name of Dye Temperature Rate 1 Rate 2
k1 lnA0 A0 r2 k2 1AoAor2
RB 30ºC 0.011 2.751 15.66 0.9796 0.0024 0.0535 0.0535 0.9998
40ºC  – –  –  –        
50ºC 0.0581 2.2391 9.38 1        
RR 30ºC 0.0056 2.8096 16.6 0.9235 0.0026 0.0321 0.0321 0.9745
40ºC 0.0057 2.804 16.51 0.9343 0.0029 0.0199 0.0199 9404
50ºC 0.0057 2.7816 16.14 0.9257 0.0036 0.0117 0.0117 0.8888
RY 30ºC 0.0066 2.8416 17.14 0.9521 0.002 0.0605 0.0605 0.9976
40ºC 0.0047 2.9044 18.25 0.9137 0.0023 0.054 0.054 0.9926
50ºC 0.0056 2.8538 17.35 0.9669 0.0024 0.0452 0.0452 9839
Table 5: summary of results from regression line equation from the linear of plot of lnA vs. Time (min), pseudo first-order reaction equation and from the linear of plot of 1A} vs. Time (min), pseudo second-order reaction equation for different Temperatures
Effluent
The r2 values were not consistent or as high, for effluent as compared the prepared solutions, this may be attributed to the salts used for fixation, in the dyeing process, that are present in the effluent. It must be noted that by changing the pH of the effluent and changing the charges of the ions present in the effluent, also changed the rate of adsorption. The correlation co-efficient for the effluent showed the adsorption process followed the pseudo first-order model than the pseudo second-order model, which is again inconsistent with the results obtained for optimization.

Name of Dye Rate 1 Rate 2
k1 lnA0 A0 r2 k2 1AoA0 r2
RB 0.0019 3.2016 24.57 0.8284 0.0168 0.306 3.2679 0.7507
RR 0.0016 3.2284 25.24 0.8551 0.0211 0.4313 2.3185 0.662
RY 0.0018 3.2054 24.67 0.855 0.0131 0.1734 5.7670 0.6
Table 6: summary of results from regression line equation from the linear of plot of lnA vs. Time (min), pseudo first-order reaction equation and from the linear of plot of 1A} vs. Time (min), pseudo second-order reaction equation for the effluent
Intraparticle Diffusion Model
Prediction of the rate determining step is important for the design purpose . The transfer is determined by either mass transfer, or in this case, intraparticle diffusion. These are shown by three steps:
Transport of the solute from the bulk solution through liquid film to the adsorbent exterior surface.

Solute diffusion into the pore of adsorbent except for a small quantity of sorption on the external surface, parallel to this is the intraparticle transport mechanism of the surface diffusion.

Sorption of the solute on the interior surfaces of the pores and capillary spaces of the adsorbent.

The rate of adsorption is controlled by the slowest step, which could be either film diffusion or pore diffusion. The adsorption of dyes onto CBP may be controlled due to film diffusion at earlier stages and as the adsorption process continues, the adsorption process may be controlled by intraparticle diffusion. ADDIN EN.CITE <EndNote><Cite><Author>Hui QUI</Author><Year>2009</Year><RecNum>168</RecNum><DisplayText>(Hui QUI 2009)</DisplayText><record><rec-number>168</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1415546611″>168</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>Hui QUI, Lu LV, Bing-cai PAN, Qing-jian ZHANG, Wei-ming ZHANG, Quan-xing ZHANG</author></authors></contributors><titles><title>Critical review inadsorption kinetic models</title><secondary-title>Journal of Zhejiang University SCIENCE A</secondary-title></titles><periodical><full-title>Journal of Zhejiang University SCIENCE A</full-title></periodical><pages>716 – 724</pages><volume>10</volume><number>5</number><dates><year>2009</year></dates><urls></urls></record></Cite></EndNote>(Hui QUI 2009)
It can be observed that the plots did not pass through the origin, this indicates some degree of boundary layer control and this then showed that the intraparticle diffusion was not the only rate limiting step, but other processes might control the rate of adsorption. The rate constant used for the intraparticle diffusion models were obtained from the pseudo second-order model which was determined earlier as the slower rate constant.
Different Initial Dye Concentration
The r2 values obtained from the linear regression line of the plot were very good (?1). It was found that the kint constant decreased with an increase in initial concentration of dye. The y-intercepts were close to the origin of the graph and constant C was close to 0.

Name of Dye Concentration KintC r2
RB 10 mg/L -1.0×10-5 0.0302 0.9666
30 mg/L -3.0×10-6 0.0196 0.997
50 mg/L -3.0×10-8 0.025 1
RR 10 mg/L -7.0×10-6 0.0049 0.9914
30 mg/L -5.0 x10-7 0.0197 0.9993
50 mg/L -3.0 x10-8 0.025 1
RY 10 mg/L -4.0 x10-7 0.005 1
30 mg/L -6.0 x10-7 0.0199 0.9998
50 mg/L -4.0 x10-8 0.0246 0.9139
Table 7: Shows the results from the linear regression line obtained intraparticle diffusion model, a plot of Qt vs. t1/2
Change in mass of CBP (adsorbent)
The r2 values increased for each dye with an increase in mass of CBP, this shows that 0.20 g of CBP was the optimum mass of CBP for the adsorption of dyes. Kint decreased with an increase in the mass of adsorbent. Even though the plot did not pass through the origin, the y-intercept was close to zero.

Name of Dye Mass of CBP KintC r2
RB 0.10 g -1.0×10-6 0.0224 0.9459
0.15 g -1.0×10-6 0.02 0.999
0.20 g -2.0×10-6 0.091 1
RR 0.10 g -1.0×10-6 0.0199 0.9971
0.15 g -9.0×10-7 0.0198 0.9988
0.20 g -9.0×10-7 0.0199 0.999
RY 0.10 g -1.0×10-6 0.0199 0.9921
0.15 g -9.0×10-7 0.0199 0.9998
0.20 g -9.0×10-7 0.0197 0.9999
Table 8: Shows the results from the linear regression line obtained intraparticle diffusion model, a plot of Qt vs. t1/2
Change in pH of dye solutions
From the r2 values obtained for each dye, the optimum parameter is a pH of 5.5, since those plots showed a r2 closest to 0. The r2 values for the a pH of 11 were very low, since no adsorption has occurred.
Name of Dye pH KintC r2
RB 2 -5.0×10-6 0.02 0.9721
5.5 -1.0×10-6 0.02 0.999
7 -5.0×10-6 0.0291 0.7684
11 – – –
RR 2 -4.0×10-6 0.0202 0.9997
5.5 -2.0×10-6 0.0198 0.9988
7 -2.0×10-6 0.0188 0.9963
11 -3.0×10-9 0.0189 0.9766
RY 2 -5.0×10-6 0.0197 0.9959
5.5 -1.0×10-6 0.0199 0.9998
7 -2.0×10-6 0.0192 0.9977
11 -3.0×10-9 0.0161 0.3097
Table 9: Shows the results from the linear regression line obtained intraparticle diffusion model, a plot of Qt vs. t1/2
Change in RPM
The Table 10 shows that 200 RPM was the optimum parameter by the increasing correlation co-efficient that is approaching or equivalent to 1 as the stirring rate was increased. The kint value increased with an increasing stirring rate of the adsorption process.
Name of Dye RPM KintC r2
RB 100 -6.0 x10-7 0.022 0.7937
150 -1.0 x10-6 0.02 0.999
200 -3.0 x10-5 0.0202 1
RR 100 -1.0 x10-6 0.0205 0.9977
150 -2.0 x10-6 0.0198 0.9988
200 -3.0 x10-6 0.0199 0.9994
RY 100 -9.0 x10-7 0.0204 0.9995
150 -1.0 x10-6 0.0199 0.9998
200 -2.0 x10-6 0.02 0.9997
Table 10: Shows the results from the linear regression line obtained intraparticle diffusion model, a plot of Qt vs. t1/2
Change in Temperature
The Table 11 shows an optimum temperature of 30ºC for RB, 30ºC for RR and 40ºC for RY. The plots were very good, as shown from the liner regression line.

Name of Dye Temperature KintC r2
RB 30ºC -2. 0x10-6 0.0196 0.9974
40ºC – –  – 
50ºC –  –  –
RR 30ºC -2.0 x10-6 0.0197 0.9993
40ºC -2.0 x10-6 0.0204 0.9915
50ºC -1.0 x10-6 0.0202 0.9956
RY 30ºC -1.0 x10-6 0.0199 0.9998
40ºC -2.0 x10-6 0.02 0.9999
50ºC -2.0 x10-6 0.0203 0.9756
Table 11: Shows the results from the linear regression line obtained intraparticle diffusion model, a plot of Qt vs. t1/2
Effluent
Based on the correlation co-efficient, RY follows the intraparticle diffusion model better than RR and RB. The intraparticle diffusion constant is the lowest for RR and the highest for RY.

Name of Dye KintC r2
RB -1.0X10-6 0.202 0.919
RR -2.0X10-6 0.0206 0.9375
RY -1.0X10-5 0.0207 0.9455
Table 12: Shows the results from the linear regression line obtained intraparticle diffusion model, a plot of Qt vs. t1/2
Adsorption Isotherms
Adsorption isotherms are the fundamental requirements for the design of an adsorption mechanism. Isotherms represent the relationship between the mass of the dye adsorbed onto an adsorbent, CBP under different experimental conditions. The shape and parameters of the isotherm provide the important information about the adsorption mechanisms, the surface properties of CBP and the affinity of the dye molecules for adsorption. PEVuZE5vdGU+PENpdGU+PEF1dGhvcj5Ub29yPC9BdXRob3I+PFllYXI+MjAxMjwvWWVhcj48UmVj
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ADDIN EN.CITE.DATA (Hui QUI 2009, Toor and Jin 2012)
The Langmuir isotherm is the simplest isotherm and is based on three assumptions:
Adsorption cannot proceed beyond a monolayer coverage
All sites are equilavant and the surface is uniform
The ability of a molecule to absorb at a given site is independent of the occupation of neighbouring sites
The Freundlich isotherm is based on the deviations of the Langmuir isotherm which is often due to the failure to follow all of Langmuir’s assumptions. The Freundlich isotherm does follow the assumption that the adsorption sites are independent and equivalent.
The higher correlation co-efficient for the Langmuir isotherm than the Freundlich isotherm represented in Tables 13 – 16 show that the adsorption process follow Langmuir isotherm and not the Freundlich isotherm. This means that the dye adsorbs as a monolayer onto the uniform equivalent sites onto the CBP.

Change in Initial Dye Concentration
Name of Dye Concentration FreundlichLangmuir
1C2 C2 lnC1 C1 r2 1V?V?1kLV?kLr2
RB 10 mg/L 0.055 18.01 4.444 85 0.851 0.009 101 0.002 3.96 1
30 mg/L 0.488 2.046 3.118 22 0.764 0.005 196 0.084 0.06 0.932
50 mg/L 2.532 0.394 4.506 90 0.551 0.012 80 0.874 0.014 0.440
RR 10 mg/L 0.117 8.517 4.357 78 0.898 0.009 105 0.004 2.375 0.990
30 mg/L 0.593 1.685 2.782 16 0.746 0.003 285 0.118 0.029 0.874
50 mg/L 2.703 0.369 5.137 170 0.515 0.022 44 0.184 0.122 0.595
RY 10 mg/L 0.021 47.169 4.539 93 1 0.009 103 0.003 2.852 1
30 mg/L 0.509 1.964 3.090 21 0.739 0.003 256 0.090 0.043 0.802
50 mg/L 0.284 3.511 3.901 49 0.849 0.027 36 1.159 0.0238 0.644
Table 13: Shows the results from linear regression line of the Freundlich Isotherm model, a plot of lnV vs. lnP and of the Langmuir Isotherm model, a plot of PV vs. P
Change in mass of CBP (adsorbent)
Name of Dye Mass of CBP FreundlichLangmuir
1C2C2lnC1 C1 r2 1V?V?1kLV?kLr2
RB 0.10 g 0.254 3.932 3.797 44 0.828 0.009 107 0.025 0.364 0.971
0.15 g 0.278 3.597 3.852 47 0.960 0.010 99 0.010 0.971 0.985
0.20 g 0.019 52.356 4.540 93 1 0.009 101 0.001 6.187 1
RR 0.10 g 0.517 1.932 3.067 21 0.882 0.005 192 0.081 0.064 0.952
0.15 g 0.374 2.671 3.586 36 0.990 0.008 121 0.034 0.240 0.999
0.20 g 0.088 11.286 4.357 78 0.997 0.010 97 0.002 3.551 0.998
RY 0.10 g 0.474 2.108 3.244 25 0.811 0.006 0.05 0.058 0.104 0.876
0.15 g 0.374 2.673 3.631 37 0.971 0.008 0.02 0.029 0.277 0.987
0.20 g 0.125 7.942 4.301 73 1 0.009 0.01 0.008 1.160 1
Table 14: Shows the results from linear regression line of the Freundlich Isotherm model, a plot of lnV vs. lnP and of the Langmuir Isotherm model, a plot of PV vs. P
Change in pH of the dye solutions
Name of Dye pH FreundlichLangmuir
1C2 C2lnC1 C1 r2 1V?V?1kLV?kLr2
RB 2 0.189 5.274 4.095 60 0.998 0.010 99 0.007 1.364 0.996
5.5 0.797 1.253 2.415 11019 0.919 0.004 222 0.092 0.048 0.857
7 1.867 0.535 0.056 1 0.777 0.012 81 0.361 0.034 0.354
11  – –   – – –   – –  – –  –
RR 2 0.163 6.105 4.142 62 0.999 0.010 98 0.007 1.342 0.995
5.5 0.927 1.078 2.007 7 0.875 0.003 277 0.114 0.031 0.825
7 1.588 0.630 0.083 1 0.894 0.008 120 0.315 0.026 0.455
11 10.11 0.099 29.08 4×1012 0.103 0.126 7 3.947 0.032 0.063
RY 2 0.193 0.193 4.133 62 0.988 0.010 0.07 0.007 1.369 0.991
5.5 0.861 0.861 2.341 10 0.919 0.003 0.09 0.090 0.042 0.802
7 1.438 1.438 0.734 2 0.868 0.002 0.14 0.146 0.017 0.395
11 0.473 0.473 2.607 13 0.001 0.025 1 1.124 0.022 0.271
Table 15: Shows the results from linear regression line of the Freundlich Isotherm model, a plot of lnV vs. lnP and of the Langmuir Isotherm model, a plot of PV vs. P
Change in RPM
Name of Dye RPM FreundlichLangmuir
1C2 C2lnC1 C1 r2 1V?V?1kLV?kLr2
RB 100 0.603 1.656 2.886 17 0.996 0.004 238 1.099 0.004 0.918
150 0.274 3.648 3.861 47 0.981 0.008 119 0.0268 0.313 0.997
200  – – –  – –  –  –  – – – 
RR 100 0.544 1.836 2.946 19 0.996 0.007 142 0.0749 0.093 0.964
150 0.395 2.528 3.539 34 0.985 0.008 121 0.0342 0.240 0.999
200 0.273 3.655 3.857 47 0.984 0.009 111 0.0215 0.418 0.991
RY 100 0.611 1.635 2.841 17 0.992 0.005 172 0.0816 0.071 0.982
150 0.419 2.386 3.528 34 0.950 0.007 137 0.039 0.187 0.989
200 0.362 2.760 3.221 25 0.977 0.007 130 0.0291 0.265 0.997
Table 15: Shows the results from linear regression line of the Freundlich Isotherm model, a plot of lnV vs. lnP and of the Langmuir Isotherm model, a plot of PV vs. P
Change in Temperature
Name of Dye Temperature FreundlichLangmuir
1C2 C2lnC1 C1 r2 1V?V?1kLV?kLr2
RB 30ºC 0.274 3.648 3.861 47 0.981 0.008 119 0.027 7×10-5
0.997
40ºC  – – –  – –   – –  – – – 
50ºC  – –  – –  –  – – –  –  –
RR 30ºC 0.395 2.527 3.540 34 0.985 0.008 121 0.034 6×10-5 0.999
40ºC 0.3904 2.562 3.5456 34 0.995 0.008 120 0.033 6×10-5 0.9977
50ºC 0.3597 2.780 3.597 36 0.998 0.008 113 0.029 7×10-5 0.994
RY 30ºC 0.419 2.386 3.529 34 0.950 0.008 121 0.029 6×10-5 0.987
40ºC 0.458 2.182 3.456 31 0.962 0.007 138 0.038 5×10-5 0.993
50ºC 0.441 2.268 3.470 32 0.978 0.007 135 0.038 5×10-5 0.996
Table 16: Shows the results from linear regression line of the Freundlich Isotherm model, a plot of lnV vs. lnP and of the Langmuir Isotherm model, a plot of PV vs. P
Effluent
The effluent shows a much better response to the Langmuir isotherm than the Freundlich isotherm. This shows that despite the other chemicals present in the effluent, it still adsorbs as a monolayer, all sites on the CBP are uniform and the chemicals do not change the adsorption properties of CBP.

Name of Dye
FreundlichLangmuir
1C2 C2lnC1 C1 r2 1V?V?1kLV?kLr2
RB 0.125 8.000 4.180 65 0.836 0.011 93 0.005 1.877 0.965
RR 0.122 8.157 4.201 66 0.799 0.011 91 0.005 2.180 0.947
RY 0.141 7.087 4.162 64 0.837 0.011 91 0.005 1.912 0.944
Table 16: Shows the results from linear regression line of the Freundlich Isotherm model, a plot of lnV vs. lnP and of the Langmuir Isotherm model, a plot of PV vs. P
Characterization of dye on CBP
The FT-IR spectrums (fig. 22) show that the dye does not chemically change the CBP but forms a layer around it, as interpreted by the Langmuir isotherm.

Figure 22: FT-IR of CBP and (a) RB, (b) RR and (c) RY
Activation Energy
The activation energies were obtained from the linear slopes from eq. 8. The positive values, shown in Table 22, show that an increase in temperature favour the adsorption of the reactive dyes onto CBP.
lnAA -Ea/R EaRR -0.7358 0.479 -1586.3 190.7987 kJ.mol-1
RY -3.2397 0.039 -896.94 107.8831 kJ.mol-1
Table 17: Shows the results from linear regression line of the Arrhenius equation, a plot of lnk2 vs. 1/T
Thermodynamics
Gibbs Free Energy
The positive Gibbs free energy values shown in Table 32 show that the adsorption process is spontaneous in the reverse reaction (desorption). These values were calculated using eq. 10.
Dye Temperature ?Gº
RB 303 K 24080.60 kJ?mol-1?K-1
RR 303 K 24020.01 kJ?mol-1?K-1
313 K 24937.67 kJ?mol-1?K-1
323 K 25420.22 kJ?mol-1?K-1
RY 303 K 24202.01 kJ?mol-1?K-1
313 K 25677.62 kJ?mol-1?K-1
323 K 26350.84 kJ?mol-1?K-1
Table 18: show the Gibbs Free Energy at each temperature T
Enthalpy and Entropy
For RY, ?S is positive and ?H is positive, a process is spontaneous at high temperatures, where exothermicity plays a small role in the balance. For RR, When ?S is negative and ?H is negative, a process is spontaneous at low temperatures, where exothermicity is important.

?S/R ?S -?H/R ?H
RR -686.06 -82.5186 -7.3587 0.885097
RY 1020.7 122.7688 -13.026 1.566755
Figure 19: Table to show Entropy and Enthalpy obtained from the linear regression line of the plot of lnkL vs. 1/T
Desorption Experiments
The adsorption experiments conducted showed that under acidic conditions, the binding of the reactive dye particles onto the CBP was easily accomplished. It would therefore, it can be assumed that under alkaline conditions the reverse would occur. This is especially true, since no adsorption occurs in alkaline conditions. Under alkaline conditions the negatively charged sites increase on the polymeric surface and acts as driving force for the electrostatic repulsion of the dye anions ADDIN EN.CITE <EndNote><Cite><Author>P</Author><Year>2011</Year><RecNum>166</RecNum><DisplayText>(P 2011)</DisplayText><record><rec-number>166</rec-number><foreign-keys><key app=”EN” db-id=”w9tvazrf5wv9doet0vip5vvre599ptztz922″ timestamp=”1415530397″>166</key></foreign-keys><ref-type name=”Journal Article”>17</ref-type><contributors><authors><author>karthikeyan M; kumar K K K &amp; Elango K P</author></authors></contributors><titles><title>Batch sorption studies on removal of furoride ions from water using eco-friendly conducting/bio-polymer composites</title><secondary-title>Desalination</secondary-title></titles><periodical><full-title>Desalination</full-title></periodical><pages>49-56</pages><volume>267</volume><dates><year>2011</year></dates><urls></urls></record></Cite></EndNote>(P 2011) :
R-NH3+-O3-S-(Dye) + OH- RNH2 + (Dye)-SO3- + H2O
Dye adsorption experiments were conducted using 0.05 mol/L and 0.10 mol/L, it was found that some desorption did occur but the dye particles were not completely removed from the CBP surface. Due to the lack of complete desorption, it can be assumed that a higher concentration of NaOH would successfully remove all of the dye particles from the surface of the CBP.
Conclusion
The adsorption kinetics were fitted to the two-step kinetic rate equation. The effects of various conditions, such as initial dye concentration, the mass of adsorbent, pH, the speed of the shaker and temperature were investigated. The rate of adsorption differed with the initial dye concentration, the lowest concentration was adsorbed the fastest. An acidic pH was favoured and a pH of 2 was found as an optimal condition for the highest rate of adsorption. The rate of adsorption increased with the Mass of adsorbent, temperature and the speed of the shaker used, these conditions could therefore increase the adsorption process. Industrial effluent containing the three dyes used in the experiments were obtained and tested under alkaline (pH 10.9), neutral (pH 7) and acidic (pH 5.5) conditions. The effluent adsorbed only under the acidic conditions.
Therefore, CBP was proven as an efficient adsorbent for removing dye particles from wastewater, as it also cost efficient.
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Nomenclature
CP Cationic Polymer
SCP Sarcosine Cationic Polymer
Cationic bentonite polymer CBP
Reactive blue 222 RB
Reactive red 195 RR
Reactive yellow 145 RY
%DR Percentage dye removed
A0Initial absorbance of the dye
AAbsorbance of dye at time (t)
C0 Initial concentrations (mg/L) of dye
Ct Concentrations (mg/L) of dye in the solution at time t
V Volume (L) of the dye solution
W Weight (g) of the CBP adsorbent
A Concentration (mg/L) of dye at time (t)
Ao Initial concentration (mg/L) of dye/ Constant
k1 Pseudo first-order rate constant
A Concentration (mg/L) of dye at time (t)
k2 Pseudo second-order rate constant
C Constant
QtAmount of dye adsorbed (mg/g)
KintIntraparticle diffusion rate constant (mg/g?min1/2)
P concentration (mg/L)
V Volume (L) of dye solution
k Constant
VVmon volume (L) of the adsorbate adsorbed over Volume (L) of adsorbate corresponding to complete monolayer coverage.

C1 Constant
C2 Constant
A pre-exponential factor
EaActivation Energy of the reaction
?S Entropy
R Constant
T Temperature
?H Enthalpy
?G Gibbs Free Energy
Appendix
Equations
Adsorption kinetics
Pseudo first-order equation
A first order reaction may be of the type:
A Z
At the beginning of the reaction (t = 0) and the concentration of A is a0 and the concentration of Z is 0. If after time t, the concentration of Z is dxdt, and therefore for the first-order reaction:
dxdt = k1A (1.1.a)
Separation of the variables gives:
dxA = k1 dt (1.1.b)
And integration gives:
-lnA = k1 t + I (1.1.c)
Where, I is the constant of integration. This constant may be evaluated using the boundary constant
-ln A0 = I (1.1.d)
And by inserting (1.1.d) into (1.1.c), it leads to:
ln AA0 = k1 t (1.1.e)
The equation can also the written as:
lnA – lnA0 = k1 t (1.1.f)
And
lnA = k1 t + lnA0 (1.1.g)
equation 1.1.g is shown as eq. 3
Pseudo second-order equation
There are now two possibilities. The rate may be proportional to the product of two equal concentrations or to the product of two different ones. The first case must occur when a single reaction is involved, as in the process:
2A Z
It may also be found in reactions between two different substances,
A + B Z
Provided their initial concentrations are the same.

In such situations the rate may be expressed as:
dxdt = k2 A2 (1.2.a)
Where, A is the initial concentration minus the reacted concentration. Separation of the variables leads to:
dxA2 = k2 dt (1.2.b)
This integrates to:
1A = k2 t + I (1.2.c)
Where, 1 is the constant of integration. The boundary condition is that x = 0 when t = 0; therefore:
I = 1A0 (1.2.d)
By inserting (1.2.d) into (1.2.c), it leads to:
1A = k2 t + 1A0 (1.2.e)
Equation 1.2.e is shown as eq. 4
Adsorption Isotherms
FreundlichThe Freundlich isotherm corresponds to the assumption that the adsorption enthalpy changes logarithmically with pressure, as shown in the extent of adsorption below:
? = C1 p1C2 (2.1.a)
Where C1 and C2 are constants. If we express the extent of adsorption:
? = VVmon (2.1.b)
The equation becomes:
VVmon = C1 p1C2 (2.1.c)
Integration:
ln VVmon = ln C1 + 1C2 lnP (2.1.d)
orln V = ln C1 + 1C2 lnP (2.1.e)
Equation (2.1.e) is then shown as eq. 7
Langmuir
The rate of change of surface coverage due to adsorption, that is:
d?dt ? partial pressure P of A
And
d?dt ? number of vacant site N(1-?)Where, N = total number of sites
Therefore:
d?dt = ka PN(1-?) (2.2.a)
Now the rate of change of ? due to desorption (the reverse reaction) is directly proportional of adsorbed species, N ?:
d?dt = – kd N? (2.2.b)
At equilibrium the net rate of adsorption is zero, that is (2.2.a ) – (2.2.b):
Ka PN (1- ?) = kd N ? (2.2.c)
(2.2.c) ÷ N
( kakd ) P (1- ?) = ? (2.2.d)
If kakd = kPkp(1-?) = ? (2.2.e)
Therefore:
KP = ? + kP ? = ? (1 + kP)
?= kP1+kP (2.2.f)
A more useful form of plotting, Langmuir isotherm is given as:
kP ? + ? = kP (2.2.g)
with ? = VVmon, where V? is the volume corresponding to complete coverage.

Then (2.2.g) becomes:PV = PV? + 1KLV? (2.2.h)
Equation (2.2.h) becomes eq. 6
Arrhenius Equation
k = Ae-Ea/RT (3.a)
This becomes:
ln k = ln A – Ea/RT (3.b)
equation (3.b) is shown as eq.8

x

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