Selective separation of arsenic and antimony enabled by desolvation effect during distillation process: chlorine/oxygen affinity mechanism

The depth-separation of arsenic from antimony is crucial for achieving high-purity antimony metal. Chlorinated distillation has shown to effectively lower arsenic levels to just a few ppm, making it a promising method for arsenic impurity removal. However, many aspects of the deep separation mechanism of arsenic remain unexplored, posing technical barriers to effective arsenic removal in high-purity antimony production. This work introduces a “chlorine/oxygen affinity selective distillation” model to elucidate the mechanism underlying arsenic and antimony separation in chloride systems. Through thermodynamic analysis and quantum chemistry calculation, we demonstrate that arsenic species in different oxidation states exhibit markedly distinct affinities for chlorine and oxygen. The critical factor is the change in the solvation structure of As 3+ as it interacts with Cl − , while the strong binding affinity between As 5+ and oxygen inhibits chloride-mediated desolvation. Thus, HCl concentration plays a pivotal role in enhancing the separation efficiency of As 3+ from Sb 3+ . Experimental results reveal that increasing HCl concentration from 5 mol/L to 7 mol/L boosts arsenic removal efficiency by 5.7 %. This mechanism may offer broader applications for the efficient separation of similar elements in chloride systems.