高效重金属捕集剂EDTC的结构表征及对酸性络合铜的去除特性研究

以乙二胺和二硫化碳为反应物,无水乙醇和去离子水的混合溶液为溶剂,制备了一种巯基类重金属捕集剂N,N-双(二硫代羧基)乙二胺(EDTC),采用紫外光谱、红外光谱和元素分析对其结构进行表征,重点研究了其对EDTA络合铜、柠檬酸络合铜和酒石酸铜3种酸性模拟络合铜的去除性能及螯合沉淀物的溶出特性,并探讨了EDTC脱除络合铜的机理.研究结果表明,处理50 mg·L-1的含铜废水,p H值范围为3~9,EDTC投加量为mEDTC/mCu=8(质量比),反应时间3 min,PAM投加量为1 mg·L-1,此时出水Cu2+浓度均低于0.25 mg·L-1,去除率达到99.5%以上.螯合沉淀物在弱酸性和弱碱性条件下很稳定,不易产生二次污染.红外光谱图分析结果表明,EDTC与Cu会发生螯合反应,即EDTC直接脱出络合铜中Cu2+,并与Cu2+生成难溶的螯合产物EDTC-Cu,进而有效地去除废水中Cu.

Structure characterization of highly-efficient heavy metal chelating agent EDTC and its removal of acid complex copper

Sulfhydryl heavy metal chelating agent of N,N'-bis(2-mercaptoethyl) ethylenediamine (EDTC) was prepared using ethylenediamine and carbon disulfide as raw materials and mixed solution of anhydrous ethyl alcohol and deionized water as solvent. The structure of EDTC was characterized by analytical and various spectral techniques such as FT-IR, UV-Vis and elementary analysis. Its performance on treating EDTA-Cu, CA-Cu (citric acid, CA) and TA-Cu (tartaric acid, TA), the stability of its chelated precipitates and the reaction mechanism of EDTC and Cu were discussed. The experimental results showed that under the conditions of pH 3~9, m_EDTC/m_Cu=8, 3 min of reaction time, 1.0 mg·L^-1 of the coagulant aid (PAM) dosage and slower stirring for 3min, EDTC had a high Cu²⁺ removal efficiency of 99.5%. The precipitates were highly stable both in weak acidic and alkaline environment, and would not cause secondary pollution. The results of IR showed chelate reaction between EDTC and Cu²⁺. Cu²⁺ was directly captured by EDTC to form insoluble chelate, so as to effectively remove Cu from wastewater.