荞麦皮生物吸附去除水中罗丹明B的吸附条件响应面法及热力学研究

Biosorption of Rhodamine-B by buckwheat hull:Response surface methodology and thermodynamics study

采用Box-Behnken响应面优化实验设计对荞麦皮生物吸附去除水中染料罗丹明B的影响因素(如温度、pH值、染料初始浓度、吸附剂用量)进行研究,建立了去除率与上述因素之间的二次多项式模型,得到荞麦皮去除罗丹明B的最佳条件为:温度50℃、pH=2、罗丹明B初始浓度100mg·L-1、吸附剂用量11.75g·L-1,最优条件下罗丹明B的最大去除率可达到92.30%.用Langmuir、Freundlich和Dubinin-Radushkevich方程对吸附等温线进行拟合,其中,Langmuir方程拟合结果最好,其最大吸附量为79.34mg·g-1.另外,计算得到了荞麦皮生物吸附水中罗丹明B的热力学状态函数ΔG0、ΔH0、ΔS0及平均吸附能E分别为-27.29～-24.84kJ·mol-1、13.29kJ·mol-1、125.60J·mol-1·K-1和11.74～12.37kJ·mol-1,结合对荞麦皮pHpzc的测定、BET分析和吸附染料前后的红外光谱变化情况,对罗丹明B在荞麦皮上的吸附机理进行了探讨.本研究结果表明,荞麦皮是一种极具潜力的绿色吸附剂,能够有效用于水中罗丹明B等染料的去除.

The effect of several important parameters on the removal of Rhodamine-B by buckwheat hull were evaluated using an optimal experimental design based on Box-Behnken Response Surface method.The factors included temperature,pH,initial dye concentration and adsorbent dosage.A quadratic model for predicting the optimum removal conditions was derived,and the obtained optimal parameters were temperature 50 ℃,pH=2.0,initial dye concentration 100 mg · L^-1,and adsorbent 11.75 g · L^-1.At the optimal conditions,the maximal removal rate of Rhodamine-B reached 92.30%.Langmuir,Freundlich and Dubinin-Radushkevich isothermal equations were applied to fit the adsorption equilibrium data.The Langmuir isotherm adsorption model was found to fit the data best,and adsorption capacity of the biosorbent was 79.34 mg · g^-1.Thermodynamic parameters were calculated for the reactions,including ΔG0（-27.29^-24.84 kJ · mol-1）,ΔH0（13.29 kJ · mol-1）,ΔS0（125.60 J · mol^-1 · K^-1 and E（11.74~12.37 kJ · mol^-1）.Finally,the removal mechanism was discussed with pHpzc,BET and FTIR analyses.This study implied that buckwheat hull is a promising sorbent for removing Rhodamine-B from water.