以亚硫酸钠为还原剂,研究采用控制电位还原法回收氯化浸出液中的贵金属.结果表明:当控制金还原电位为530~550 mV时,氯化浸出液中98%以上的Au将被还原沉淀至粗金粉中,同时Pt、Pd和Te基本不被还原沉淀,所得粗金粉中Au含量在98%以上,Se、Te、Cu和Pb等杂质的含量均低于0.10%(质量分数),而且该金还原电位对不同Au浓度或酸度的氯化浸出液都具有良好的适应性;然后当控制铂钯还原电位为390~420 mV时,金还原后液中的Au、Pt和Pd将被还原沉淀至1 mg/L以下,而Te基本不被还原,所得铂钯精矿中贵金属含量高、杂质含量少,且所确定的铂钯还原电位对不同铂钯浓度或酸度的金还原后液以及反应温度均具备较好的适应性.可见,通过控制电位还原,可将氯化浸出液中贵金属选择性沉淀并与其他元素初步分离.
Using sodium sulfite as the reducing agent, the recovery of noble metals in chlorination-leaching solution by potential-controlled reduction was investigated. The results show that, when the reduction potential of Au is controlled at 530?550 mV, 98% Au in the chlorination-leaching solution is reduced and precipitated as raw-gold powder while Pt, Pd and Te are almost not reduced. The content of Au in the obtained raw-gold powder is above 98% and those of Se, Te, Cu and Pb are all lower than 0.10% (mass fraction). Also, the potential value of gold reduction has good adaptability to many different kinds of the chlorination-leaching solutions that have various concentrations of Au or H+. Then, when the reduction potential of Pt/Pd is controlled in 390?420 mV, the concentration of Au, Pt and Pd in the precipitated-gold solution can be reduced to below 1 mg/L while most of Te still remains. The content of noble metals in the collected Pt-Pd concentrate is remarkably high and that of impurities is comparatively low. In addition, the determined potential value of Pt/Pd reduction exhibits greatly adaptable to those precipitated-gold solutions with different Pt/Pd concentrations or acidity as well as reaction temperature. Accordingly, the noble metals in chlorination-leaching solutions will selectively precipitate and preliminarily separate from other elements by potential-controlled reduction method.
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