重金属絮凝剂DTAPAM去除水中Cu-EDTA的条件优化和机理  

Condition optimization and mechanism of heavy metal flocculant DTAPAM in the removal of Cu-EDTA from water.

作　　者：张航 王刚[1] 周雅琦 马玉 ZHANG Hang;WANG Gang;ZHOU Ya-qi;MA Yu(School of Environmental and Municipal Engineering,Lanzhou Jiaotong University,Lanzhou 730070,China)

机构地区：[1]兰州交通大学环境与市政工程学院,甘肃兰州730070

出　　处：《中国环境科学》2023年第2期532-543,共12页China Environmental Science

基　　金：国家自然科学基金资助项目(51368030);兰州交通大学天佑创新团队资助项目(TY202005)。

摘　　要：工业含Cu废水中常含有配位剂EDTA,可与Cu(Ⅱ)配位后形成稳定的可溶性配合物Cu-EDTA,致使废水中的Cu(Ⅱ)较难被除去.为了将含Cu-EDTA废水中的Cu(Ⅱ)得以有效去除,采用二硫代羧基化胺甲基聚丙烯酰胺(DTAPAM)作为重金属絮凝剂,以Cu-EDTA为处理对象,研究了絮凝水力条件、DTAPAM投加量、pH值、EDTA浓度、Cu(Ⅱ)初始浓度对DTAPAM去除Cu-EDTA性能的影响,确定了Cu(Ⅱ)的最佳去除条件;并利用紫外-可见吸收光谱、红外光谱、扫描电镜及能谱分析等表征方法探究了DTAPAM去除Cu-EDTA的机理.结果表明,最佳絮凝水力条件为快搅时间2min、快搅速度160r/min、慢搅时间20min、慢搅速度50r/min;当pH值为5.0~7.0时,DTAPAM对Cu(Ⅱ)初始浓度为25mg/L的含Cu-EDTA水样的去除性能均较好,且在pH值为7.0时Cu(Ⅱ)的去除效果最好,最高去除率可达99.07%;当体系中EDTA与Cu(Ⅱ)配位比为1:1时,DTAPAM对不同Cu(Ⅱ)初始浓度的含Cu-EDTA水样均具有理想的去除效果.表征结果显示,DTAPAM高分子链中的二硫代羧基(—CSS-)与水样中Cu(Ⅱ)发生了螯合反应;pH值为2.0~9.0时,DTAPAM-Cu螯合稳定常数的对数值介于13.09~13.71.DTAPAM处理含Cu-EDTA水样时,DTAPAM先与EDTA发生配位竞争作用,将Cu-EDTA中的Cu(Ⅱ)解络出与之发生螯合反应生成絮体沉淀物,絮体间发生以吸附架桥和网捕卷扫为主的絮凝作用,促进絮体的沉降,提高了Cu(Ⅱ)的去除.The coordination agent EDTA is usually found in industrial wastewater containing copper, and the stable soluble compound Cu-EDTA can be formed between EDTA and Cu(Ⅱ), which makes it difficult to remove Cu(Ⅱ) from the wastewater. In order to improve effectively the removal of Cu(Ⅱ) from Cu-EDTA wastewater, dithiocarboxyl aminomethy-polyacrylamide(DTAPAM) was employed as heavy metal flocculant. The effects of hydraulic conditions, DTAPAM dosage, pH value, EDTA concentration, and initial Cu(Ⅱ) concentration on the removal performance of Cu-EDTA with DTAPAM were investigated, and the optimal removal conditions for Cu-EDTA in water sample were determined. The removal mechanism of Cu-EDTA with DTAPAM was also explored by using some characterization methods, such as UV, IR, SEM and EDS. The results show that the optimal hydraulic conditions were as follows: the fast stirring time was 2min, the fast stirring speed was 160r/min, the slow stirring time was 20min, and the slow stirring speed was 50r/min. The removal performance of Cu-EDTA by DTAPAM was favorable for the initial Cu(Ⅱ) concentration of 25mg/L at pH 5.0~7.0, and the highest removal rate of Cu(Ⅱ) reached 99.07% at pH 7.0. When the coordination ratio between EDTA and Cu(Ⅱ) was 1:1, it had the ideal removal efficiency for Cu-EDTA with DTAPAM at different initial Cu(Ⅱ) concentrations. The characterization results show that the chelation reaction should occur between Cu(Ⅱ) and dithiocarboxylic groups(-CSS-) on the molecular chain of DTAPAM. At pH 2.0~9.0, the logarithm values of the chelation stability constant for DTAPAM-Cu were in the range of 13.09~13.71. For the removal mechanism of Cu-EDTA by DTAPAM, Cu(Ⅱ) was replaced from Cu-EDTA by DTAPAM due to coordination competition, and the flocs were formed though chelation reaction between Cu(Ⅱ) and DTAPAM. In addition, the adsorption bridging and net sweeping among flocs played a major role in the flocculation,which promoted the settlement of the flocs and improved the removal rate of Cu(Ⅱ).

关 键 词：重金属絮凝剂 Cu-EDTA 稳定常数 螯合沉淀 配位竞争 

分 类 号：X703[环境科学与工程—环境工程]