摘要
硫脲对金、银、铜的反萃取能力和体系的酸度有关。利用此特点,通过调节体系酸度并采用分段反萃取可达到金与银、铜的基本分离。反萃取过程的适宜工艺条件为:温度60℃;反应时间大于5min;流比1/3;硫脲浓度1.2mol/L;酸度0.5mol/L HCl(反萃液Ⅰ)和1.5mol/L HCl和(反萃液Ⅱ)。负载有机相经两段共五级逆流反萃取后,金、银、铜的反萃率均达99.8%以上。将反萃体系在高流比混合澄清器中进行小规模生产性试验,结果与模拟平衡值相近,级效率达95%。用电沉积法将硫脲液中金和银、铜按不同的槽电压进行分离,所得硫脲贫液经调整后可返回反萃体系,反萃能力不受影响。
Both theoretical analyses and experimental results showed that SC(NH_2)_2 can replace CN- in R_3CH_3NM(CN)_2 forming R_3CH_3N^+ and M(SC(NH_2)_2)_2^+ under acidic condition. The stripping ability of thiourea is related to acidity and Au can be separated from Ag, Cu by controlling acidity and adopting two-step successive stripping. It was found that when the concentration of SC(NH_2)_2 was 1.2 mol/L; that of HCl was 0.5 mol/L(stripping solution Ⅰ) and 1.5 mol/L(stripping solution Ⅱ); t>5 min and flow ratio of V_A/V_O = 1/3, at a temperature of 60 ℃ under moderate agitation, the stripping effeciencies of Au, Ag, Cu were all over 99.8% with five-stage countercurrent stripping. The small-scale test of stripping in a high flow ratio vertical mixer-settler was carried out and it is concluded that the experimental results agree with the simulated equilibrium data, the stage effeciecy would reach 95%. Au, Ag and Cu were finally recovered and completely separated from each other by electrowinning using different bath voltages and the acidified thiourea solution can be used again for recycling.
关键词
硫脲
反萃取
季铵盐
萃取剂
extraction
thioureas
extractive agent
gold
silver
copper
quaternary ammonium compounds
stripping