超声辅助EDDS/EGTA淋洗对土壤重金属形态、环境风险的影响及响应面优化

采用响应面法实验设计研究了超声辅助EDDS/EGTA淋洗对Cu、Zn、Pb和Cd等不同重金属的洗脱效果和对残留重金属化学形态分布的影响,以超声功率、初始pH、EDDS投加量、EGTA投加量作为考察对象,以各重金属去除率及其环境风险削减率为响应值进行了模拟和优化.结果表明,EDDS对Pb的洗脱效率最高,Cu、Zn次之,Cd最低;EGTA对Cd的洗脱效率最高,Pb、Zn次之,Cu最低;超声功率对Cu、Pb去除强化效果明显,对Cd影响小,对Zn无显著影响;初始pH值为酸性时,Cu和Zn去除率高,碱性时Pb去除率较高,Cd去除率有所下降.EDDS与EGTA投加量及EGTA投加量与初始pH值对环境风险总削减率存在交互作用.超声辅助EDDS/EGTA对可还原态重金属洗脱效果较好,但容易导致弱酸提取态Cu和Pb残留率有所升高.响应面优化结果表明,当EDDS和EGTA投加量分别为重金属总摩尔数的1.92和2.56倍、超声功率为600 W、淋洗液初始pH值为5.27时,环境风险总削减率达到77.58%,与模拟值相近,模型具有较好的模拟和预测能力.

Effects of ultrasound-assisted EDDS/EGTA washing on specification and environmental of heavy metals in soil and optimization by response surface method

The response surface method was used to design an experiment and investigate the effect of ultrasound-assisted EDDS/EGTA washing on the removal efficiency of heavy metals including Cu, Zn, Pb and Cd in soil and the specification of residual heavy metals. Taking the ultrasonic power, initial pH, EDDS dose and EGTA dose as the factors, and the removal rate of heavy metals and environmental risk as the response values, the relationship between response values and factors was fitted and optimized. The results showed that the removal efficiency of Pb by EDDS was the highest, following by Cu and Zn, and Cd was the lowest. The EGTA showed the highest removal rate of Cd, following by Pb, Zn and Cu. The ultrasonic power showed significant removal effect on Cu and Pb, little effect on Cd, and no significant effect on Zn. The removal rates of Cu and Zn were high under acid condition. Under alkaline condition, the removal rate of Pb was high while the removal rate of Cd decreased. The ultrasound-assisted EDDS/EGTA showed high washing efficiency of heavy metals in reducible state, but may lead to the increase of copper and lead in weak acid extractable state. EDDS and EGTA, EGTA and initial pH both showed interaction effect on reduction rate of the total environmental risk. The response surface optimization results showed that the optimal washing condition was as following:the EDDS dose was 1.92, the EGTA dose was 2.56, the ultrasonic power was 600 W and the initial pH was 5.27, the reduction rate of total environmental risk was 77.58%, which was similar to the simulated value. Therefore, the model has good fitting and predicting ability.