6种低分子有机酸对针铁矿、蒙脱石和生物炭中结合态Cd活化效果的对比

选择3种常用的土壤重金属稳定介质针铁矿、蒙脱石和生物炭，首先通过吸附实验使其对Cd达到吸附平衡（8、16和4 h），并通过氯化镁洗脱获得稳定结合的Cd（2.52、0.93和1.04 mg·g-1）。随后分别用柠檬酸、苹果酸、马来酸、酒石酸、草酸、琥珀酸6种常见的植物根际低分子有机酸进行结合态Cd活化实验，测定活化率和活化量，对比活化效果。结果表明，6种低分子有机酸对针铁矿、蒙脱石、生物炭中结合态Cd的活化效果随浓度的增加而增加，其中柠檬酸的活化作用最大，其次为草酸，其余4种酸的活化效果差异不显著。柠檬酸随浓度增加，其对Cd活化率的线性增长率最高，在针铁矿、蒙脱石、生物炭中分别为1.74%、4.71%、2.12%。在250 μmol·L-1时，柠檬酸对针铁矿、蒙脱石、生物炭3种材料中Cd的活化率分别达到4.2%、11.0%、5.6%。对比研究表明，针铁矿吸附Cd效率高且稳定，蒙脱石吸附Cd效率低且易于被低分子有机酸活化。

Comparison of activation effects of six kinds of low molecular weight organic acids on Cd bound to goethite,montmorillonite and biochar

Three commonly used stable mediums for remediation of soil heavy metals including goethite, montmorillonite and biochar were selected to investigate the activation effects of cadmium (Cd) stably bound to them by six low molecular weight organic acids (citric acid, malic acid, maleic acid, tartaric acid, oxalic acid and succinic acid respectively) which were often released by root of plants. The adsorption equilibrium (8, 16 and 4 h) of Cd on the three mediums was obtained by adsorption experiment. The Cd stably bound to mediums (2.52, 0.93 and 1.04 mg·g-1) was obtained by MgCl2 elution. Subsequently, the quantity of Cd activated by six low molecular weight organic acids was measured. The results showed that the activation of Cd bound to goethite, montmorillonite and biochar by six acids increased significantly with elevated acid concentrations. Citric acid had the highest activation effect, followed by oxalic acid, while the rest had no significant effects. The linear increase rate of citric acid with increasing concentrations was the highest, with the time of 1.74%, 4.71% and 2.12% in goethite, montmorillonite and biochar, respectively. The activation rates of Cd bound to goethite, montmorillonite and biochar were 4.2%, 11.0% and 5.6%, respectively at 250 μmol·L-1of citric acid. In general, goethite adsorbed Cd with higher efficiency and stability, while the Cd adsorption by montmorillonite was relatively low and easily activated by low molecular weight organic acids.