探究油菜秸秆髓芯、 外壳、 籽荚对水溶液中Pb(Ⅱ)的吸附能力及其吸附机理。 以水溶液中Pb(Ⅱ)最大去除率为评价指标, 采用响应面法Box-Behnken Design实验来分析溶液pH、 Pb(Ⅱ)初始浓度、 粒径大小、 油菜秸秆各部位投加量和时间因素对油菜秸秆吸附Pb(Ⅱ)的影响程度并建立多元回归模型, 优化出最佳吸附条件参数组合; 应用吸附动力学、 等温吸附线模型来拟合油菜秸秆各部位对Pb(Ⅱ)吸附过程, 评价其吸附行为; 用红外光谱对吸附水溶液中Pb(Ⅱ)前后的油菜秸秆髓芯、 外壳、 籽荚进行表征, 探讨其基团变化情况。 结果表明: 水溶液pH与油菜秸秆髓芯、 外壳、 籽荚的投加量两个因素是影响油菜秸秆对水溶液中Pb(Ⅱ)去除的关键因素。 模型回归决定系数分别是R2髓芯=0.9664, R2外壳=0.970 1, R2籽荚=0.964 9, 方程拟合较好, 模型可用。 油菜秸秆髓芯、 外壳、 籽荚对Pb(Ⅱ)的吸附行为符合二阶动力学方程与Langmuir等温线模型, 对水溶液中Pb(Ⅱ)最大吸附量分别为135.14, 78.74和90.09 mg·g-1。 通过比较油菜秸秆髓芯、 外壳、 籽荚吸附水溶液中Pb(Ⅱ)前后红外光谱图发现, 油菜秸秆各部位基团(羟基、 羧基、 酰胺等基团)发生了峰波数位移、 强度降低的变化, 提示这些基团在吸附水溶液Pb(Ⅱ)过程中发挥重要作用。

In this study, the adsorption of lead(Ⅱ) from aqueous solution by rape straw powders was investigated. Box-Behnken Design(BBD) accompanied by response surface methodology (RSM) were employed to optimize various environmental conditions for biosorption of pH, concentration of lead ions, particle size, biosorbents loading and contact time using rape straw powders as absorbent. The models of kinetics and isotherms were used to evaluate the behaviors of biosorbent for uptaking lead(Ⅱ) from aqueous solution by rape straw powders. The functional groups of rape straw powders which played roles were recognized by Fourier transform infrared spectra. The results revealed that the parameters of pH and biosorbents loading were the key factors affecting the efficiency for the removal of lead(Ⅱ) from aqueous solution. R2 were 0.966 4, 0.970 1 and 0.964 9 for uptaking lead(Ⅱ) from aqueous solution by rape straw pith core, shell and seed pods, respectively, indicated the validity of the model. The experimental data was better described by a pseudo-second-order model compared with the intraparticle diffusion model. In comparing the analysis of Langmuir and Freundlich isotherms, the adsorption of lead ions showed a better fit with the Langmuir isotherm model. According to the Langmuir equation, the maximum adsorption capacities of rape straw pith core, shell and seed pods for uptaking lead(Ⅱ) from aqueous solution were 135.14, 78.74, 90.09 mg·g-1, respectively. Comparing the graphs of infrared spectroscopy of straw pith core, shell and seed pods before and after the Pb(Ⅱ) removal, we discovered that the spectra changed, particularly active groups, such as hydroxy, carboxyl and amide groups of the protein, which played major roles in the biosorption process. The study of results provided evidences that rape straw powders can be used for removing Pb(Ⅱ) from sewage water.