Selective separation of antimony from a Sb-Fe mixed solution by hydrolysis and application in the hydrometallurgical process of antimony extraction

In this study, the hydrolysis of Sb to form Sb4Cl2O5 from a Sb-Fe mixed solution was first investigated using NH4OH as a neutralizer. The effects of different process parameters on the hydrolysis ratio of antimony, separation coefficient of Sb-Fe and product features were investigated in detail. The results indicated that the hydrolysis ratio of antimony and Fe was higher than 99.0% and lower than 0.1% under the optimized conditions: hydrolysis temperature of 30 °C, final pH of 0.5, and neutralizer dropping speed of 1.33 mL/min. The residual content of Sb was 0.12 g/L, and the hydrolysis exhibited high selectivity and completeness. Then, the Sb4Cl2O5 generated was further converted to Sb2O3 by using Na2CO3, NaOH and NH4OH as conversion agents. The antimony oxide product had an excellent crystal form and high purity. Lastly, this hydrolysis - transformation method was applied for Sb recovery from a post-electrowinning solution obtained from a wet Sb smelter that showed a continuous increase in Fe iron concentration caused by Fe ore leaching in stibnite, and an open loop for solution purification must be used. High purity (above 99.5%) and fine (below 100 μm) Sb2O3 was obtained that met commercial antimony white standards.