Dutra A J B, Rocha G P, Pombo F R
Federal University of Rio de Janeiro, Department of Metallurgical and Materials Engineering, Cidade Universitária, C.T., sala F210, 21949-900 Rio de Janeiro, RJ, Brazil.
J Hazard Mater. 2008 Apr 1;152(2):648-55. doi: 10.1016/j.jhazmat.2007.07.030. Epub 2007 Jul 17.
Copper-cyanide bleed streams arise from contaminated baths from industrial electroplating processes due to the buildup of impurities during continuous operation. These streams present an elevated concentration of carbonate, cyanide and copper, constituting a heavy hazard, which has to be treated for cyanide destruction and heavy metals removal, according to the local environmental laws. In the Brazilian Mint, bleed streams are treated with sodium hypochlorite, to destroy cyanide and precipitate copper hydroxide, a solid hazardous waste that has to be disposed properly in a landfill or treated for metal recovery. In this paper, a laboratory-scale electrolytic cell was developed to remove the copper from the bleed stream of the electroplating unit of the Brazilian Mint, permitting its reutilization in the plant and decreasing the amount of sludge to waste. Under favorable conditions copper recoveries around 99.9% were achieved, with an energy consumption of about 11 kWh/kg, after a 5-h electrolysis of a bath containing copper and total cyanide concentrations of 26 and 27 g/L, respectively. Additionally, a substantial reduction of the cyanide concentration was also achieved, decreasing the pollution load and final treatment costs.
由于在连续运行过程中杂质的积累，工业电镀工艺中受污染的镀液会产生含铜氰化物的排放流。这些排放流中碳酸盐、氰化物和铜的浓度升高，构成了重大危害，根据当地环境法律，必须对其进行处理以破坏氰化物并去除重金属。在巴西造币厂，排放流用次氯酸钠处理，以破坏氰化物并沉淀氢氧化铜，这是一种固体危险废物，必须妥善处置在垃圾填埋场或进行金属回收处理。本文开发了一种实验室规模的电解槽，用于从巴西造币厂电镀单元的排放流中去除铜，使其能够在工厂中重新利用，并减少污泥的产生量。在有利条件下，对分别含有26 g/L和27 g/L铜和总氰化物浓度的镀液进行5小时电解后，铜回收率达到约99.9%，能耗约为11 kWh/kg。此外，氰化物浓度也大幅降低，减少了污染负荷和最终处理成本。
