复配Na_2S-DDTC处理高浓度含Ni电镀废水

Na_2S-DDTC composite agents for treatment of electroplating wastewater with high Ni concentrations

为降低实际工程中二硫代氨基甲酸盐(DTC)类螯合剂用药成本,以某电镀厂高浓度含络合Ni电镀漂洗废水作为处理对象,研究了一种有机巯基类螯合剂(简称DDTC)复配Na_2S去除Ni离子的效果与机理,并重点对反应pH、DDTC与Na_2S单独、复配投加量、含Ni初始浓度等几个因素的影响进行探究。实验结果表明:反应pH值对Ni的去除有较大影响,pH=9.0时Na_2S-DDTC对Ni的去除效果最好;Na_2S-DDTC对电镀络合Ni具有很好的捕集功能,优于Na_2S、DDTC单独使用,其中当pH=9.0,nNa_2S/nNi=1.5,ρ(DDTC)=200 mg·L^(-1)时,Ni的剩余浓度为0.062 mg·L^(-1),达到《电镀污染物排放标准》(GB 21900-2008)中关于Ni污染物特别排放限值要求(<0.1 mg·L^(-1));Na_2S-DDTC处理不同初始浓度的含Ni废水具有较宽的应用范围,其中Na_2S对Ni的用量存在nNa_2S/nNi=1.5的化学计量关系,DDTC存在不同的最佳投药量;Na_2S与DDTC复配使用具有一定的协同作用。

In the effort to reduce the cost of the dithiocarbamate（ DTC） class chelating agent in actual projects,we studied the effectiveness and the mechanisms to remove the Ni ion from a type of organic sulfhydryl chelating agent（ DDTC）,compounding with Na2 S. We employed the wastewater from an electroplating factory,containing high-density electroplating complexation Ni,as the treatment object. The research focused on various factors,such as the reaction pH,separate and compound dosages of Na2 S and DDTC,and the initial concentration of the Ni content. The experimental results showed that the reaction pH strongly influenced the removal of Ni,and at pH 9. 0,the Na_2S-DDTC compound was superior for removing Ni. The Na_2S-DDTC compound has an efficient trapping function for electroplating complexation Ni,which was superior to using Na2 S and DDTC separately.The residual Ni concentrations were 0. 062 mg · L- 1when pH = 9. 0,nNa_2S/ nNi= 1. 5,ρ（ DDTC） = 200mg·L- 1,which could conform to the Ni special discharge standard for electroplating（ GB 21900-2008）（ 0. 1mg·L- 1）. The Na_2S-DDTC compound has a wider application range for treating wastewater that contains different initial concentrations of Ni. A stoichiometric relation was shown between Na2 S and the dosage of Ni,namely,nNa_2S/ nNi= 1. 5,and the optimal coagulant dose for DDTC was different. Compounding Na2 S with DDTC had a certain synergistic effect.