Exploring arsenic removal behavior in purification process of antimony metal through vacuum volatilization

Abstract

This paper proposes a straightforward model that can describe the arsenic(As) impurity behavior during the vacuum volatilization purification process of antimony (Sb) metal. This model aims to determine the optimal degree of volatilization and predict As impurity concentration in the purified Sb metal. Vacuum volatilization experiments were conducted to verify this model at the volatilization temperatures of 700 °C, 730 °C, and 760 °C. The research results indicated that, the concentrations of As impurity in both residue and volatile exhibit an exponentially decreasing trend throughout the entire volatilization process; the decrease in the condensing temperature at the different locations of volatiles leads to an increase in As impurity concentration, which is accompanied by the variations in crystal morphology; there is a good agreement between the calculated and experimental results in the residues, which the mean standard deviations are ± 0.025, ±0.094, and ± 0.148 respectively at the above volatilization temperatures; the calculated results are much higher than the experimental results in the volatiles due to the calculated separation coefficient without the consideration of kinetic factor; the optimal volatilization degrees of 36.50 %, 35.95 %, and 38.44 % respectively result in volatilization removal rates and residual rates both exceeding 60 %; Upon the volatilization degrees are equal to 36.94 %, 30.28 %, and 47.09 %, As impurity decreases from the initial concentrations of 27.82 mg/kg, 22.90 mg/kg, and 35.08 mg/kg to the ultimate concentrations of 10 mg/kg respectively, which meets the purity standard of 4.5 N (99.995 %). Consequently, this model can quantitatively predict As impurity concentration in the purified Sb metal, which provides the theoretical guidance for the As removal from Sb metal by vacuum volatilization.