生物可降解螯合剂谷氨酸N,N-二乙酸四钠对污泥中重金属萃取效率的研究

Extraction of Heavy Metals from Sludge Using Biodegradable Chelating Agent N,N-bis( carboxymethyl) Glutamic Acid Tetrasodium

谷氨酸N,N-二乙酸四钠(GLDA)具有较强金属螯合能力,是新一代生物可降解绿色螯合剂.通过分批提取实验对GLDA去除工业污泥中Cd、Ni、Cu、Zn的萃取过程进行研究,考察了萃取时间、萃取体系p H值、螯合剂用量等因素对重金属萃取效果的影响,并采用修正的BCR连续提取法分析萃取前后污泥中重金属的形态.结果表明,GLDA对污泥中Cd具有良好的去除效果;体系在p H=4,螯合剂与重金属总量摩尔比为3∶1的条件下,多种重金属取得最佳萃取效果;Zn主要以残渣态存在,导致该金属萃取率低;螯合能力不仅与萃取时间,萃取体系p H值,螯合剂用量,螯合常数等因素有关,而且还与金属的形态分布有关.

N, N-bis ( carboxymethyl) glutamic acid tetrasodium ( GLDA), a novel biodegradable and green chelating agent, has excellent metal chelating ability. Batch experiment was conducted to study the extraction process of Cd, Ni, Cu and Zn in industrial sludge using GLDA. The effects of contact time, pH of the system, content of chelating agent were investigated, and the forms of heavy metals in sludge pre- and post-extraction using the modified BCR sequential extraction procedure were studied. The results showed that GLDA was effective for cadmium extraction in sludge. Several heavy metals could be effectively extracted under the condition of pH 4 and molar ratio of chelating agent to total heavy metal 3: 1. Residual fraction took the largest fraction in Zn, which caused the low extraction efficiency of this metal. Chelating properties were related not only to contact time, pH, chelating agent’s concentration, and stability constant but also to species distribution of metals.