两种离子液体对Cd2+在四种土壤上吸附的影响

研究了2,3-吡啶二羧酸和咪唑-4,5-二羧酸两种离子液体阳离子部分对Cd~(2+)在四种不同性质土壤上吸附的影响。结果表明,离子液体的存在显著影响了Cd~(2+)在土壤中的吸附,与对照相比,添加1 mmol·L-12,3-吡啶二羧酸使得Cd~(2+)在武进漂洗型水稻土、吴县潴育型水稻土、南京黄褐土和宜兴棕红壤四种土壤上的最大吸附量分别降低209、834、667、509 mg·kg~(-1),而添加1 mmol·L~(-1)咪唑-4,5-二羧酸使Cd~(2+)最大吸附量分别降低226、54、124、81 mg·kg~(-1),2,3-吡啶二羧酸对Cd~(2+)在供试土壤上吸附量的影响显著大于咪唑-4,5-二羧酸。基于离子选择电极分析了平衡液中自由态Cd~(2+)含量,发现两种离子液体都能与Cd~(2+)络合,从而降低平衡液中Cd~(2+)含量,其中2,3-吡啶二羧酸与Cd~(2+)的络合能力大于咪唑-4,5-二羧酸。两种离子液体进入环境,会使Cd~(2+)在土壤上的吸附量减少,从而增加Cd~(2+)的移动性和环境风险。

Effects of two ionic liquids on Cd2+ adsorption on four soils

The effects of 2,3-Pyridinedicarboxylic acid and 4,5-Imidazoledicarboxylic acid on Cd²⁺ adsorption on four soils with different characteristics(Wujin, Wuxian, Nanjing and Yixing soils) were investigated. Results showed that the adsorption of Cd²⁺ on soils depended on the characteristics of soils. The presence of ionic liquids significantly affected the adsorption of Cd²⁺ on soils. Compared with the control, the presence of 1 mmol·L^-1 2,3-Pyridinedicarboxylic acid reduced the maximum adsorption of Cd²⁺ on Wujin, Wuxian, Nanjing and Yixing soils by 209, 834, 667 and 509 mg·kg^-1, respectively, whereas adding 1 mmol·L^-1 4,5-Imidazoledicarboxylic acid decreased the maximum Cd²⁺ adsorption by 226, 54, 124 and 81 mg·kg^-1 on Wujin, Wuxian, Nanjing, and Yixing soils, respectively. Therefore, 2,3-Pyridinedicarboxylic acid showed greater effects on Cd²⁺ adsorption on tested soils than 4,5-Imidazoledicarboxylic acid did. The free Cd²⁺ ions in the equilibrium solution measured by Cd ion selective electrode showed that both ionic liquids were able to complex with Cd²⁺, leading to decreased Cd²⁺ ion concentrations in soil solution, and consequently reduced Cd²⁺ adsorption on soils. The complexing capability of 2,3-Pyridinedicarboxylic was stronger than that of 4,5-Imidazoledicarboxylic acid, which resulted in greater inhibition of Cd²⁺ sorption on soils. Our results indicate that ionic liquids could decrease the adsorption of Cd²⁺ on soils, but increase the mobilization and environmental risk of soil Cd²⁺.