两种螯合剂单独和复合浸提土壤重金属效果的研究

为揭示土壤重金属的浸出规律,采用振荡浸提方法,研究了三聚磷酸钠(STPP)和乙二胺四乙酸钠(Na2EDTA)对土壤中Pb、Cd和Cu的浸出效果,重点考察混合液浓度、振荡时间、p H对土壤重金属浸出率的影响,并比较浸提前后重金属的存在形态。结果表明:Na2EDTA和STPP均能将土壤中重金属离子浸出,其中STPP的浸出能力较小;浸提剂浓度为5 mmol·L-1时,混合液对Pb、Cd和Cu的浸出率均高于同浓度的Na2EDTA、STPP单独浸提的浸出率;当浸提剂浓度大于10 mmol·L-1时,混合液对Pb、Cu的浸出率低于同浓度的Na2EDTA、STPP单独浸提的浸出率;混合浸提剂对重金属的浸出率随p H的升高有所降低,浓度为10 mmol·L-1、振动时间为2 h较为适宜;混合浸提剂主要浸出酸可交换态、还原态、氧化态的重金属,能较大程度地降低土壤中重金属的含量。

Extraction of heavy metals from polluted soil by Na2EDTA and STPP

Remediation of heavy metal polluted soils is critical to ensuring food and ecological security. In this study, the performance of sodium phosphate(STPP) and ethylenediamine sodium oxalate(Na₂EDTA) alone and in combination on Pb, Cd and Cu extraction from soil was examined by batch extraction method. The effects of extractant concentration, reaction time and pH on the extraction efficiencies of heavy metals were also investigated. The changes of heavy metal fractions in soil before and after extraction were determined. Results indicated that both Na₂EDTA and STPP had positive effects on extraction of heavy metal ions from polluted soil. The extraction capacity of heavy metals was lower for STPP than Na₂EDTA, but was higher for combined extractant than single extractants at 5 mmol·L-1. However, the Pb and Cu extraction efficiencies were lower for combined than single extractants at concentration over 10 mmol·L-1. Raising pH decreased the extraction efficiency of combined extractant. The optimum extraction efficiency for combined extractant was found to be 5 mmol·L-1 of mixture concentration and 2 h vibration. The combined extractant reduced soil heavy metals through removing acid-exchangeable, reductable, and oxidizable fractions of heavy metals.