焦磷酸钾对铜污染土壤的淋洗修复

Removal of copper from contaminated soil with potassium pyrophosphate as chelating ligand

焦磷酸钾是一种对农田土壤环境友好的物质。通过批处理振荡淋洗实验研究了所配制的焦磷酸钾淋洗液对模拟污染土壤中重金属铜的淋洗特性,探讨了淋洗时间、淋洗液pH和焦磷酸钾浓度对淋洗效果的影响,并讨论了土壤中铜在焦磷酸钾淋洗液作用下的解吸动力学和淋洗前后重金属形态变化特性。结果表明,淋洗时间越长、淋洗液浓度越大,淋洗效果越好。优化实验条件,淋洗浸提24 h、淋洗液pH为7.0、n(焦磷酸钾)∶n(铜)为7∶1,淋洗效果较好,铜淋洗率为40.51%。焦磷酸钾淋洗的铜主要以酸提取态和可还原态为主。焦磷酸钾淋洗液对土壤铜的浸提过程符合双常数方程,说明土壤中铜在焦磷酸钾淋洗液作用下的解吸是非均相扩散过程。

Potassium pyrophosphate is considered to be environmentally friendly. In this work,the extraction of copper from simulated contaminated soil by pyrophosphate was investigated. The effect of extraction time,pH,and pyrophosphate concentration as well as the desorption kinetics and the change in the species distributions were examined. The results showed that the removal efficiency increased with the extraction time and chelating agent concentration. Under the optimized conditions,the extraction efficiency was highest at a pH of 7. 0,extraction time of 24 h,and complexant-to-metal ratio of 7 ∶ 1. Sequential fractionation of the treated and untreated soil samples indicated that the copper in the acid-extractable fraction and reducible fraction was removed effectively by pyrophosphate. A two-constant equation was the best model for describing the desorption kinetics of copper by pyrophosphate,revealing that the desorption process was heterogeneous diffusion.