关键词: 螯合剂, 矿山水体底泥, 重金属污染, 淋洗液回收

Abstract: In order to remove the heavy metals in bottom mud of mine water bodies non-pollutionally,three kinds of chelating agents namely EDTA,GLDA and MGDA,were used to extract heavy metals Cd,Cu and Ni under various conditions, while analyzing their underlying mechanisms. Experimental methods such as batch extraction and BCR extraction were used to compare and analyze the influence of EDTA,GLDA and MGDA,as well as different factors,on the efficiency of heavy metal extraction from mine water sediments. The results revealed that the optimal leaching time varied depending on the heavy metal element and the chelating agent used. pH was identified as the primary influencing factor for chelating agent efficiency in heavy metal extraction. Additionally,an increase in chelating agent concentration significantly improved the removal rate of heavy metals,with cumulative cyclic leaching resulting in a minimal improvement of less than 5% in heavy metal removal efficiency. The chelating agents facilitated the removal of heavy metals from mine water sediments by altering the speciation of heavy metals. Under ambient temperature conditions,the most suitable conditions for the three chelating agents were as follows:for EDTA, leaching time of 16 hours,pH = 4,n(EDTA) ∶n(HMs)= 6 ∶1,with two cycles of leaching;for GLDA,leaching time of 8 hours, pH = 4,n(GLDA) ∶n(HMs)= 4 ∶1,with three cycles of leaching;for MGDA,leaching time of 8 hours,pH = 4,n( MGDA) ∶n (HMs)= 6 ∶1,with three cycles of leaching. Under these optimal conditions,the removal rates for Cd from great to small were in the order EDTA,GLDA and MGDA,for Cu,MGDA,EDTA and GLDA,and for Ni,MGDA,GLDA and EDTA. Green chelating agents GLDA and MGDA demonstrated their potential to replace traditional chelating agent EDTA,offering improved costeffectiveness and environmental friendliness. Following treatment with Na2S,heavy metal recovery rates exceeding 95% were achieved,with the heavy metal content in the leachate meeting national discharge standards and thus suitable for direct disposal. The findings of this study provide valuable theoretical support for the application of chelating agents in the removal of heavy metal pollution from mine water sediments.

Key words: chelating agents,mining water sediment,heavy metal pollution,leachate treatment