铅锌矿尾渣重金属在化学萃取前后的形态变化特征

采用3种常见的萃取剂EDTA,HNO3和CaCl2,在一定的萃取条件下,对永州铅锌矿尾渣土壤进行萃取实验,并采用优化的BCR连续萃取方案对萃取前后的Pb,Zn和Cd进行金属形态分析,研究3种萃取剂对Pb,Zn和Cd的萃取效率及萃取前后的形态变化特征.结果发现,3种萃取剂的萃取效率依次为EDTA>HNO3>CaCl2;EDTA不仅能萃取酸溶解态的金属,还能萃取部分铁-锰氧化物结合态、硫化物及有机结合态和残渣态的金属;HNO3和CaCl2则主要对酸溶解态的金属有一定去除效果.

Redistribution of Metals after Chemical Extraction in Tailing Soils

Under the same extractable conditions,EDTA,HNO_3 and CaCl_2 were used as the extractants to remove Pb,Zn and Cd from the tailing soils.The distribution of Pb,Zn and Cd were determined using the optimized BCR sequential extraction procedures before and after extraction.The extractability of the extractants was: EDTA > HNO_3 > CaCl_2.The results indicated that EDTA was an effective extracting agent.After EDTA extraction,the proportion of Pb,Zn and Cd in the four fractions varied considerably,which was related to the strong extraction and complexation ability.The percentage of Pb,Zn and Cd in reducible fraction,oxidizable fraction and residual fraction remained similar before and after extraction with HNO_3 and CaCl_2,which showed that HNO_3 and CaCl_2 could only extract the metal in acid extractable fraction.