稻壳生物炭吸附无机汞和甲基汞的特征研究

为了探究稻壳生物炭吸附溶液无机汞(Hg²⁺)和甲基汞(MeHg⁺)的特征,研究了不同稻壳生物炭用量和溶液pH对汞吸附的影响,及其吸附动力学和热力学特征。结果表明:当溶液中无机汞浓度为50 mg/L且pH为7.0时,施用50 mg生物炭后,生物炭对无机汞的吸附在18 h后达到平衡且最大吸附量为23.52 mg/g;当溶液中甲基汞浓度为30 ng/L且pH为4.0时,施用20 mg生物炭后,生物炭对甲基汞的吸附量在3 h后达到吸附平衡且最大吸附量为58.54 ng/g。生物炭对无机汞和甲基汞的吸附研究过程均符合准一级、准二级模型,其中准二级模型的拟合效果更好,说明该吸附作用过程更倾向于化学吸附。Freundlich和Langmuir等温吸附模型都能很好的拟合稻壳生物炭对无机汞的等温吸附,而稻壳生物炭对甲基汞的吸附符合Langmuir等温吸附模型。稻壳生物炭对总汞和甲基汞的吸附机制主要为离子交换、静电吸附、沉淀以及络合作用。研究结果可为稻壳生物炭修复汞污染环境提供理论依据。

The Characteristic of Adsorption of Inorganic Mercury and Methylmercury by Rice Husk Biochar

In order to investigate the adsorption characteristics of inorganic mercury (Hg²⁺) and methylmercury (MeHg⁺) by rice husk biochar, the effects of different amount of rice husk biochar and solution pH on the adsorption of mercury, as well as the adsorption kinetics and thermodynamics characteristics were studied. The results showed that when the concentration of inorganic mercury in the solution was 50 mg/L and the pH was 7.0, the adsorption of inorganic mercury by biochar reached equilibrium after 18 h and the maximum adsorption capacity was 23.52 mg/g. When the concentration of methylmercury in the solution was 30 ng/L and the pH was 4.0 and 20 mg biochar was applied, the adsorption capacity of biochar on methylmercury reached equilibrium after 3 h and the maximum adsorption capacity was 58.54 ng/g. The adsorption processes of inorganic mercury and methylmercury by biochar were well described by the quasi-first-order model and the quasi-second-order model, in which the first model is more reliable, indicating that the adsorption process is dominated by chemical adsorption. Both Freundlich and Langmuir isothermal adsorption models can depict the isothermal adsorption of rice husk biochar to inorganic mercury, while the adsorption of methyl mercury by rice husk biochar is fitted by Langmuir isothermal adsorption model. The mechanisms of adsorption of total mercury and MeHg by rice-hull biochar include ion exchange, electrostatic adherence, precipitation and complexation. The results from this study provide a theoretical basis for remediation of mercury polluted environment by rice husk biochar.