Singh Vandana, Sharma Ajit Kumar, Sanghi Rashmi
Department of Chemistry, University of Allahabad, Allahabad 211002, India.
J Hazard Mater. 2009 Jul 15;166(1):327-35. doi: 10.1016/j.jhazmat.2008.11.026. Epub 2008 Nov 18.
In the present communication we report on the optimization of persulfate/ascorbic acid initiated synthesis of chitosan-graft-poly(acrylamide) (Ch-g-PAM) and its application in the removal of azo dyes. The optimum yield of the copolymer was obtained using 16 x 10(-2)M acrylamide, 3.0 x 10(-2)M ascorbic acid, 2.4 x 10(-3)M K(2)S(2)O(8) and 0.1g chitosan in 25 mL of 5% aqueous formic acid at 45+/-0.2 degrees C. Ch-g-PAM remained water insoluble even under highly acidic conditions and could efficiently remove Remazol violet and Procion yellow dyes from the aqueous solutions over a pH range of 3-8 in contrast to chitosan (Ch) which showed pH dependent adsorption. The adsorption data of the Ch-g-PAM and Ch for both the dyes were modeled by Langmuir and Freundlich isotherms where the data fitted better to Langmuir isotherms. To understand the adsorption behavior of Ch-g-PAM, adsorption of Remazol violet on to the copolymer was optimized and the kinetic and thermodynamic studies were carried out taking Ch as reference. Both Ch-g-PAM and Ch followed pseudo-second-order adsorption kinetics. The thermodynamic study revealed a positive heat of adsorption (Delta H degrees), a positive DeltaS degrees and a negative Delta G degrees, indicating spontaneous and endothermic nature of the adsorption of RV dye on to the Ch-g-PAM. The Ch-g-PAM was found to be very efficient in removing color from real industrial wastewater as well, though the interfering ions present in the wastewater slightly hindered its adsorption capacity. The data from regeneration efficiencies for ten cycles evidenced the high reusability of the copolymer in the treatment of waste water laden with even high concentrations of dye.
在本通讯中，我们报道了过硫酸盐/抗坏血酸引发的壳聚糖接枝聚丙烯酰胺（Ch-g-PAM）合成的优化及其在偶氮染料去除中的应用。使用16×10⁻²M丙烯酰胺、3.0×10⁻²M抗坏血酸、2.4×10⁻³M K₂S₂O₈和0.1g壳聚糖，在25mL 5%的甲酸水溶液中，于45±0.2℃下获得了共聚物的最佳产率。即使在高酸性条件下，Ch-g-PAM仍不溶于水，并且与壳聚糖（Ch）相比，壳聚糖的吸附表现出pH依赖性，而Ch-g-PAM能在3 - 8的pH范围内有效地从水溶液中去除雷马素紫和普施安黄染料。Ch-g-PAM和Ch对两种染料的吸附数据均用朗缪尔和弗伦德利希等温线进行建模，其中数据更符合朗缪尔等温线。为了解Ch-g-PAM的吸附行为，以Ch为参考，对雷马素紫在该共聚物上的吸附进行了优化，并进行了动力学和热力学研究。Ch-g-PAM和Ch均遵循准二级吸附动力学。热力学研究表明吸附热（ΔH°）为正、ΔS°为正且ΔG°为负，表明RV染料在Ch-g-PAM上的吸附是自发的且吸热的。尽管废水中存在的干扰离子略微阻碍了其吸附能力，但发现Ch-g-PAM在去除实际工业废水中的颜色方面也非常有效。十个循环的再生效率数据证明了该共聚物在处理含有高浓度染料的废水时具有高可重复使用性。
