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研究论文

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

摘要：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100 mg·L^-1,吸附剂用量11.75 g·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79.34 mg·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~ -24.84 kJ·mol^-1、13.29 kJ·mol^-1、125.60 J·mol^-1·K^-1和11.74~12.37 kJ·mol^-1,结合对荞麦皮pH_pzc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.

Abstract：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 pH_pzc, BET and FTIR analyses. This study implied that buckwheat hull is a promising sorbent for removing Rhodamine-B from water.

Key words：buckwheat hull adsorption Rhodamine-B response surface methodology thermodynanamics