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Efficient cadmium(II) removal from aqueous solution using microwave synthesized guar gum-graft-poly(ethylacrylate) / Vandana Singh in Industrial & engineering chemistry research, Vol. 48 N° 10 (Mai 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 10 (Mai 2009) . - pp. 4688–4696 Titre : Efficient cadmium(II) removal from aqueous solution using microwave synthesized guar gum-graft-poly(ethylacrylate) Type de document : texte imprimé Auteurs : Vandana Singh, Auteur ; Ajit Kumar Sharma, Auteur ; Sadhana Maurya, Auteur Année de publication : 2009 Article en page(s) : pp. 4688–4696 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Ethylacrylate  Guar  gum  Cadmium  concentration Résumé : Microwave induced emulsion copolymerization of ethylacrylate and guar gum resulted in copolymer samples of different % grafting (%G) by changing ethylacrylate and guar gum concentrations at fixed microwave power (100%) and exposure time (15 s). The synthesis was done in the absence of any redox initiator/catalyst, and the adsorption behavior of the copolymer (295%G) was investigated by performing both the kinetics and equilibrium studies in batch conditions. Several experimental parameters such as contact time, initial cadmium concentration, temperature, adsorbent dose, electrolyte amount, and pH of the solution were varied to optimize the adsorption conditions. The most favorable pH for the adsorption was pH 9, and at this pH the adsorption data were modeled using Langmuir and Freundlich isotherms. The data fitted satisfactorily to both the isotherms, indicating that the real heterogeneous nature of the surface sites involved in the metal uptake and overall sorption of Cd(II) on the adsorbent was complex and involved more than one mechanism. On the basis of the Langmuir model, Q0 was calculated to be 714.28 mg/g for microwave synthesized copolymer (mwGG-g-PEA) in comparison to 270.27 for conventionally synthesized copolymer (cvGG-g-PEA), revealing the advantage of using microwaves in the adsorbent synthesis. The sorption by mwGG-g-PEA followed pseudo-second-order kinetics where a linear plot of t/(qt) versus t was obtained, the correlation coefficient (R2) and rate constant at 100 mg/L Cd(II) being 0.9978 and 4.6 × 10−4 g/mg/min, respectively. The adsorbent exhibited high reusability and could be successfully recycled for nine cycles where in the ninth cycle 38% adsorption was feasible. To understand the role of PEA grafts (in the copolymer) in the adsorption process, different %G samples were evaluated as adsorbent under optimized conditions. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801416z [article] Efficient cadmium(II) removal from aqueous solution using microwave synthesized guar gum-graft-poly(ethylacrylate) [texte imprimé] / Vandana Singh, Auteur ; Ajit Kumar Sharma, Auteur ; Sadhana Maurya, Auteur . - 2009 . - pp. 4688–4696. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 10 (Mai 2009) . - pp. 4688–4696 Mots-clés : Ethylacrylate  Guar  gum  Cadmium  concentration Résumé : Microwave induced emulsion copolymerization of ethylacrylate and guar gum resulted in copolymer samples of different % grafting (%G) by changing ethylacrylate and guar gum concentrations at fixed microwave power (100%) and exposure time (15 s). The synthesis was done in the absence of any redox initiator/catalyst, and the adsorption behavior of the copolymer (295%G) was investigated by performing both the kinetics and equilibrium studies in batch conditions. Several experimental parameters such as contact time, initial cadmium concentration, temperature, adsorbent dose, electrolyte amount, and pH of the solution were varied to optimize the adsorption conditions. The most favorable pH for the adsorption was pH 9, and at this pH the adsorption data were modeled using Langmuir and Freundlich isotherms. The data fitted satisfactorily to both the isotherms, indicating that the real heterogeneous nature of the surface sites involved in the metal uptake and overall sorption of Cd(II) on the adsorbent was complex and involved more than one mechanism. On the basis of the Langmuir model, Q0 was calculated to be 714.28 mg/g for microwave synthesized copolymer (mwGG-g-PEA) in comparison to 270.27 for conventionally synthesized copolymer (cvGG-g-PEA), revealing the advantage of using microwaves in the adsorbent synthesis. The sorption by mwGG-g-PEA followed pseudo-second-order kinetics where a linear plot of t/(qt) versus t was obtained, the correlation coefficient (R2) and rate constant at 100 mg/L Cd(II) being 0.9978 and 4.6 × 10−4 g/mg/min, respectively. The adsorbent exhibited high reusability and could be successfully recycled for nine cycles where in the ninth cycle 38% adsorption was feasible. To understand the role of PEA grafts (in the copolymer) in the adsorption process, different %G samples were evaluated as adsorbent under optimized conditions. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801416z

Efficient chromium(VI) adsorption by cassia marginata seed gum functionalized with poly(methylmethacrylate) using microwave irradiation / Vandana Singh in Industrial & engineering chemistry research, Vol. 47 n°15 (Août 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 n°15 (Août 2008) . - p. 5267–5276 Titre : Efficient chromium(VI) adsorption by cassia marginata seed gum functionalized with poly(methylmethacrylate) using microwave irradiation Type de document : texte imprimé Auteurs : Vandana Singh, Auteur ; Ajit Kumar Sharma, Auteur ; Premlata Kumari, Auteur Année de publication : 2008 Article en page(s) : p. 5267–5276 Note générale : Bibliogr. p. 5275-5276 Langues : Anglais (eng) Mots-clés : Chromium(VI)  treatment  methods  --  toxic  sludge;  Cassia  marginata  seed  gum  --  biosorbent  derived;  Aqueous  solution Résumé : Increasing cost of the chemicals and production of toxic sludge in the Cr(VI) treatment methods have attracted attention toward the use of biosorbents for Cr(VI) removal. The present study evaluates a novel biosorbent derived from Cassia marginata seed gum in the removal of Cr(VI) from the aqueous solution and wastewater. The adsorbent was synthesized using microwave irradiation in the absence of any radical initiator or catalyst in good yield. Adsorbents of different performances could be obtained by varying the amount of the methylmethacrylate, microwave power, and exposure time. A representative sample of microwave synthesized adsorbent was characterized using FTIR, XRD, TGA, and SEM analysis. Cr(VI) sorption was optimized using the copolymer sample of highest grafting ratio and efficiency (270% G and 59.65% E) where the removal was found to be pH and concentration dependent, pH 1.0 being the optimum value at which from 20 mL of 100 ppm Cr(VI) solution, 16.94 mg/g Cr(VI), could be removed using 5 g/L adsorbent dose at 30 °C. The adsorption data followed both Langmuir (R2 = 0.9703) and Freundlich isotherms (R2 = 0.8957) probably due to the real heterogeneous nature of the surface sites involved in the metal uptake, and overall sorption of Cr(VI) on the biosorbent is complex and involves more than one mechanisms. The adsorption followed second order kinetics, the rate constant being 0.10 × 10−5 g/(mg min) at 100 mg/L Cr(VI) concentration. The adsorbent was also found efficient in Cr(VI) removal from real industrial wastewater. Used copolymer was recycled after stripping off the adsorbed chromium with 2 M NaOH where after each cycle a successive decrease in the binding capacity was observed. To understand the advantage of using microwaves in the adsorbent synthesis, the copolymer synthesized using a K2S2O8/ascorbic acid redox pair at identical monomer concentrations (220% G and 48.6% E) was also evaluated as Cr(VI) sorbent, and the results obtained were compared with that of microwave synthesized copolymer. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie070467j [article] Efficient chromium(VI) adsorption by cassia marginata seed gum functionalized with poly(methylmethacrylate) using microwave irradiation [texte imprimé] / Vandana Singh, Auteur ; Ajit Kumar Sharma, Auteur ; Premlata Kumari, Auteur . - 2008 . - p. 5267–5276. Bibliogr. p. 5275-5276 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°15 (Août 2008) . - p. 5267–5276 Mots-clés : Chromium(VI)  treatment  methods  --  toxic  sludge;  Cassia  marginata  seed  gum  --  biosorbent  derived;  Aqueous  solution Résumé : Increasing cost of the chemicals and production of toxic sludge in the Cr(VI) treatment methods have attracted attention toward the use of biosorbents for Cr(VI) removal. The present study evaluates a novel biosorbent derived from Cassia marginata seed gum in the removal of Cr(VI) from the aqueous solution and wastewater. The adsorbent was synthesized using microwave irradiation in the absence of any radical initiator or catalyst in good yield. Adsorbents of different performances could be obtained by varying the amount of the methylmethacrylate, microwave power, and exposure time. A representative sample of microwave synthesized adsorbent was characterized using FTIR, XRD, TGA, and SEM analysis. Cr(VI) sorption was optimized using the copolymer sample of highest grafting ratio and efficiency (270% G and 59.65% E) where the removal was found to be pH and concentration dependent, pH 1.0 being the optimum value at which from 20 mL of 100 ppm Cr(VI) solution, 16.94 mg/g Cr(VI), could be removed using 5 g/L adsorbent dose at 30 °C. The adsorption data followed both Langmuir (R2 = 0.9703) and Freundlich isotherms (R2 = 0.8957) probably due to the real heterogeneous nature of the surface sites involved in the metal uptake, and overall sorption of Cr(VI) on the biosorbent is complex and involves more than one mechanisms. The adsorption followed second order kinetics, the rate constant being 0.10 × 10−5 g/(mg min) at 100 mg/L Cr(VI) concentration. The adsorbent was also found efficient in Cr(VI) removal from real industrial wastewater. Used copolymer was recycled after stripping off the adsorbed chromium with 2 M NaOH where after each cycle a successive decrease in the binding capacity was observed. To understand the advantage of using microwaves in the adsorbent synthesis, the copolymer synthesized using a K2S2O8/ascorbic acid redox pair at identical monomer concentrations (220% G and 48.6% E) was also evaluated as Cr(VI) sorbent, and the results obtained were compared with that of microwave synthesized copolymer. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie070467j