A novel model of bismuth and lead impurities removal behavior in purification of antimony metal by vacuum distillation

Abstract

Behavior models of bismuth (Bi) and lead (Pb) impurities in the residue and distillate during the vacuum distillation purification of antimony (Sb) metal were established from the prospective of thermodynamic. The verification experiments of five times vacuum distillation purification had been successively carried out using the crude Sb metal and its residues as the raw materials. Finally, the application of impurity behavior model in the distillate was discussed in detail. The research results indicated that, the concentrations variations of Bi and Pb impurities in the residues and distillates both present the same exponentially increasing phenomenon as the distillation proceeds; the experimental results are lower than the calculated results in the residues, while the experimental results are greater than the calculated results in the distillates, which Pb impurity has a better agreement than Bi impurity; when the residue fraction is controlled to over 30%, Bi and Pb impurities concentrations in the distillates can be limited to under 2.50 mg/kg and 0.43 mg/kg in present experiment according to impurity behavior model in the distillate, which the removal rates are 70.65% and 90.52% respectively. Therefore, controlling the residue fraction in the vacuum distillation purification is key to the massive production of high-purity Sb metal.