硫化物沉淀法处理含EDTA的重金属废水

在运用MINTEQA2模型对模拟重金属废水和EDTA萃取液中重金属离子形态进行分析的基础上，选用Na₂S沉淀法处理含EDTA的重金属废水. 结果表明:没有含EDTA的重金属废水，Cd2＋，Cu2＋，Pb2＋和Zn2＋是重金属离子的主要形态；而在含EDTA的模拟重金属废水和重金属萃取液中，重金属络合物是重金属离子的主要形态. 在c(EDTA)为0的条件下，Cd2＋，Cu2＋和Pb2＋的去除率达到100%，而Zn2＋的去除率仅为57.0%；随着c(EDTA)的增加，相同c(Na₂S)对废水中重金属的去除率逐渐下降. 在一定c(EDTA)的条件下，废水中重金属的去除率随着c(Na₂S)的增加而增加；但是在相同c(Na₂S)的条件下，Zn2＋的去除率较Cd2＋，Cu2＋和Pb2＋低. 工程实例进一步表明，Na₂S能够有效去除含EDTA重金属萃取液中的重金属离子，而完全去除Zn2＋则需要高浓度的Na₂S. 

Treatment of Heavy Metals from Wastewater Containing EDTA with Sulfide Precipitation

On the base of analysis of species distributions of heavy metals in solutions with MINTEQA2 computer programme at working condition, Na₂S addition wasused to remove metals from wastewater containing EDTA solution. The results showed that metal ion Cd2+, Cu2+, Pb2+, and Zn2+ were main species in the simulatedwastewater without EDTA solution. However, metal-EDTA was found to be predominant fraction among metal species in the simulated wastewater with EDTA solution. Heavy metals Cd2+, Cu2+, Pb2+ were precipitated completely by low concentration of Na₂S from without EDTA solution, and 57.0% of Zn2+ was removed. The precipitation percentages of heavy metals decreased with the increasing EDTA concentration. However, the removal of heavy metals increased with increasing Na₂S concentration. At the same condition, the precipitation percentages of Zn by Na₂S addition were lower than those of other metals. According to engineering experimental results, metals and EDTA were separated efficiently by Na₂S addition from the extraction solution. However, high concentration of Na₂S was required to remove all the metals including Zn.