壳聚糖吸附酸性大红及Cu^2＋对吸附的增强作用

Adsorption of Acid Red 3R on Chitosan and Its Enhancement by Cu^(2+) Co-sorption

采用壳聚糖去除水中酸性大红,对壳聚糖吸附酸性大红的动力学、热力学以及溶液pH、盐浓度、外来Cu2+对吸附的影响进行了研究.准二级吸附动力模型、Langmuir、Freundlich及Dubinin-Radushkevich (D-R)方程分别用来对吸附动力学和等温线进行分析.结果表明,酸性大红在壳聚糖上的吸附是一个化学吸附控制的准二级动力学过程.Langmuir、Freundlich和D-R方程都能较好地描述吸附等温线.溶液pH和温度对吸附有较大影响,而氯化钠浓度对吸附的影响较小.对吸附热力函数的计算结果显示ΔH0<0,表明吸附是一个放热过程.由D-R方程计算的吸附自由能E为9.5~10.7 kJ.mol-1,表明吸附过程为离子交换化学吸附.Cu2+对吸附的影响结果显示Cu2+能显著提高壳聚糖对酸性大红的吸附容量,另外建立了Cu2+浓度与吸附量增加之间的数学模型.

Chitosan was used for the removal of Acid Red 3R from aqueous solutions.Batch adsorption studies were carried out to investigate adsorption kinetics and thermodynamics and the effect of coexisting pH,NaCl,and Cu^2＋ on adsorption.Experimental data were exploited for kinetic and thermodynamic evaluations related to the adsorption processes.The kinetic data correlated well with the pseudo-second-order kinetic model,indicating the chemical sorption via complex formation/ion exchange.The equilibrium data were well fitted by three isotherm models,namely,Langmuir,Freundlich and Dubinin-Radushkevich（D-R） equations.Moreover,adsorption of Acid Red 3R onto the chitosan was found to be strongly depending on solution temperature and pH.However,the addition of sodium chloride was found to have little effect on the adsorption process.Thermodynamic studies revealed the adsorption process was exothermic in natural.The adsorption free energies derived from D-R equation were in range of 9.5-10.7kJ·mol^-1, implying that the sorption process is a chemical ion-exchange mechanism.In addition,adsorption capacity of chitosan to Acid Red 3R was found to be greatly enhanced in the presence of Cu^2＋.A model correlating the concentration of Cu^2＋ with the enhanced amount of dye adsorbed was established.