响应面法优化胡敏素对Cu^(2+)的吸附及机理研究

The study of adsorption mechanism of Cu(Ⅱ) from aqueous solutions by humin with response surface methodology

采用Box-Behnken响应面优化实验设计对胡敏素吸附去除水中Cu^(2+)的过程进行了优化,设定吸附时间、吸附剂用量、pH、温度和Cu^(2+)初始浓度为5个影响因素,Cu^(2+)吸附率为响应值,建立了吸附率与上述因素之间的二次多项式模型,确定最佳吸附条件,对吸附过程的等温模型及吸附机理进行了研究.响应面分析表明,吸附剂用量、pH和Cu^(2+)初始浓度是显著因素.胡敏素对Cu^(2+)吸附的最佳条件为:吸附时间110 min、吸附剂用量2.4 g·L^(-1)、pH=5.4、温度25.0℃、Cu^(2+)初始浓度208 mg·L^(-1).在该条件下,测得胡敏素对Cu^(2+)的吸附率可达到80.78%,吸附符合Langmuir等温线方程.胡敏素表面疏松多孔,有利于其通过物理吸附方式吸附Cu^(2+),同时,胡敏素表面的羟基、羧基和羰基等活性基团可以与Cu^(2+)发生配位络合作用,Na+、Ca^(2+)、Mg^(2+)等与Cu^(2+)发生离子交换作用,从而发生化学吸附.研究结果表明,胡敏素作为一种绿色、高效、廉价的吸附剂,可应用于Cu^(2+)污染废水的治理.

The Box-Behnken design methodology including five factors： adsorption time,adsorbent dosage,pH,temperature and initial concentration of Cu^2＋was employed to study the adsorption rate of Cu^2＋from aqueous solution by humin. A quadratic model about the adsorption rate associated with the above factors was derived,through which the optimum adsorption conditions was gained. The adsorption isotherms and mechanism were also studied.Results of the response surface analysis indicate adsorbent dosage,pH and initial concentration of Cu^2＋as significant factors. The adsorption rate reached80.78% at the optimized conditions of adsorption time 110 min,adsorbent dosage 2.4 g·L^-1,pH= 5.4,temperature 25.0 ℃ and initial concentration of Cu^2＋208 mg·L^-1.The adsorption performance was well fitted with the Langmuir isotherm model. Physical adsorption occurred readily on the loose and porous surface of humin,on which active groups such as hydroxyl,carboxyl,and carbonyl group participated absorption by complexation with Cu^2＋,accompanied by ion exchange of Na^＋,Ca^2＋,Mg^2＋ ions with Cu^2＋simultaneously. It is revealed that humin is a green,effective and low-cost absorbent for the treatment of Cu^2＋contaminated water.