Removal of Cu, Ni and Zn directly from acidic electroplating wastewater by Oligo-Ethyleneamine dithiocarbamate (OEDTC)

Abstract

Traditional chemical precipitation generates a large volume of sludge required by further hazardous waste disposal. For reducing this drawback, four oligo-ethyleneamine dithiocarbamates (OEDTC), including ethylenediamine-dithiocarbamate (E1-DTC), diethylenetriamine-dithiocarbamate (E2-DTC), triethylenetetramine-dithiocarbamate (E3-DTC) and tetraethylenepentamine-dithiocarbamate (E4-DTC) were synthesized to remove Cu, Ni and Zn directly from acidic wastewater. Based on S dose, which was an essential element for metal removal, the treatment effectiveness order of the four OEDTC for Cu and Ni was E1-DTC > E2-DTC > E4-DTC > E3-DTC. The theoretical molar ratios of S toward Cu, Ni and Zn for the completed metal removal from single component were 1.5:1, 2:1, 2.2:1 for E1-DTC; 2:1, 2.6:1, 2.9:1 for E2-DTC; 2:2, 3:1, 3.9:1 for E3-DTC; and 2:1, 2.7:1, 2.8 for E4-DTC, respectively. The four OEDTC had marked preference for Cu over Ni and Zn from multiple components of simulated wastewater. They showed high removal efficiency for the complex-formed Ni and Zn from actual electroplating wastewater, yielding the effluent residual 0.003–0.008 and 0.021–0.046 mg/L, respectively. When the four OEDTC were precipitated with the three metals, FT-IR suggested the coordination of metals with S and SEM indicated densely packed particle formation. The yielded OEDTC-metals sludge enriched with heavy metals exhibited potential to be recycled.