N,N-双(二硫代羧基)乙二胺对微量络合镍的深度脱除特性研究

以柠檬酸镍(CA-Ni)、酒石酸镍(TA-Ni)、焦磷酸镍(SP-Ni)3种低浓度模拟络合镍废水为研究对象,选用自制的重金属捕集剂N,N-双(二硫代羧基)乙二胺(EDTC),对废水中的Ni进行深度脱除.重点研究了EDTC投加量、初始p H、反应时间对Ni去除效果的影响及螯合沉淀物的沉淀性能和溶出特性,同时分析了EDTC去除络合Ni的机理.研究结果表明,处理初始浓度5 mg·L~(-1)的CA-Ni、TA-Ni、SP-Ni,p H为4~8,EDTC最佳投加量分别为60 mg·L~(-1)、55 mg·L~(-1)和70 mg·L~(-1),PAM(聚丙烯酰胺)为1 mg·L~(-1),反应时间2 min,Ni的出水浓度均低于0.05mg·L~(-1),去除率达99%以上.螯合沉淀物沉降性能好且在弱酸弱碱条件下能稳定存在.红外光谱图和元素分析结果表明:EDTC与Ni发生螯合反应,即EDTC直接脱除络合镍中的Ni2+,并与Ni2+生成更稳定的螯合产物EDTC-Ni,进而有效地去除废水中Ni.

Characterizing the deep removal of trace complex nickel ions by N, N'-bis-(dithiocarboxy) ethylenediamine

A heavy metal chelating agent, N, N''-bis-(dithiocarboxy) ethylenediamine (EDTC), was synthesized to remove trace complex nickel from CA-Ni (citric acid, CA), TA-Ni(tartaric acid, TA), and SP-Ni (pyrophosphate, SP)simulated wastewater. Effect of EDTC dosage, pH and reaction time on Ni removal was investigated through single factor batch experiment. Besides, the stability and sedimentation property of chelated precipitates and the reaction mechanism of EDTC and Ni were also introduced. The optimized condition was under EDTC dosages of 60 mg·L^-1, 55 mg·L^-1 and 70 mg·L^-1, respectively, pH 4~8, 2 min of reaction time and 1.0 mg·L^-1 of the coagulant (polyacrylamide, PAM). The residual Ni²⁺concentration could decrease to less than 0.05 mg·L^-1 from the initial concentration of 5.0 mg·L^-1, with the corresponding removal efficiency over 99%.The precipitates performed excellent sedimentation property and strong stability in both weak acidic and alkaline environment. The results of IR and organic elemental analysis indicate that the chelating reaction could take place between EDTC and Ni²⁺, and Ni²⁺ was directly captured from complex nickel ions, forming an insoluble chelation with EDTC. Therefore the Ni²⁺ was removed efficiently.