油菜秸杆外壳对水溶液中六价铬的吸附作用

为探讨油菜秸秆外壳去除水溶液中重金属铬的可能性及其影响因素,并研究其吸附性能和吸附机制.采用Box-Behnken Design实验设计研究了水溶液中六价铬Cr(VI)]初始浓度、pH值范围、油菜秸秆外壳添加量和吸附温度4个因素对油菜秸秆外壳去除溶液中Cr(VI)的影响作用;用吸附等温方程、吸附动力学方程与热力学方程分别探讨了油菜秸秆外壳去除水溶液中Cr(VI)的行为;采用红外光谱技术对油菜秸秆外壳吸附水溶液Cr(VI)前后进行表征,探讨其吸附机制.油菜秸秆外壳去除溶液中Cr(VI)的最佳条件组合为:在吸附时间为1440min时,Cr(VI)初始浓度为99.15mg/L、pH值为1.01、油菜秸秆外壳添加量为2.90g/L和吸附温度35.70℃,Cr(VI)去除率为91.97%;吸附等温线拟合,吸附Cr(VI)行为符合Freundlich方程,为优惠吸附;热力学研究表明:溶液中Cr(VI)吸附属吸热反应,且为自发吸附行为;吸附动力学显示:油菜秸秆外壳去除溶液Cr(VI)符合准二阶动力学方程,吸附过程中存在离子交换;红外光谱提示:吸附过程中,O—H、C—H、NH3+、N—H和C—O基团与Cr(VI) 络合吸附发挥了重要作用.油菜秸秆外壳能够有效吸附水溶液中的Cr(VI),pH值是最为重要的影响因素.

Adsorption of Cr(VI) in the aqueous solution by rape straw shell powder.

Adsorption of Cr(VI) in aqueous solution by rape straw shell powder had been studied. The effects of initial Cr(VI) concentration, pH, absorbent dosage, and adsorption temperature on the adsorption of Cr(VI) ion by rape straw shell powder was investigated and optimized with the method of Box-Behnken Design. The models of isotherm, kinetics and thermodynamics were employed to assess the efficiency and study mechanism of action on the removal Cr(VI) in the aqueous solution by rape straw shell powder. The changes in the functional groups of rape straw shell powder formulations were identified by Fourier transform infrared spectra. The optimal conditions for the removal of Cr(VI) were found to be initial Cr(VI) concentration of 99.15mg/L, pH 1.01, adsorbent dosage of 2.90g/L and adsorption temperature of 35.70℃ during 1440min of adsorption. Under these conditions, the percentage of removal of Cr(VI) reached 91.97%. The equilibrium data were optimally illustrated by the Freundlich isotherm model, which represents an optimal and heterogeneous adsorption; The results from thermodynamic study indicated that the adsorption process was spontaneous and endothermic in nature under experimental conditions. It was found that a pseudo-second order kinetic model was the proper approach for determining the adsorption kinetics and ion exchange. The functional groups of rape straw shell powder, O—H, C—H, NH3+, N—H and C—O played a major role in adsorption of Cr(VI). The results revealed that rape straw shell powder is an effective adsorbent for removing Cr(VI) in water due to its high adsorption capacity, and pH is the key factor for affecting the efficiency for the removal of Cr(VI).