The volatilization law of standard impurity elements in 3 N antimony during vacuum distillation and preparing antimony with 4 N8 content

Abstract

A novel process for the production of high purity antimony (99.998 wt%) from crude antimony (3 N) by a two-step vacuum distillation was proposed. The process involves the volatilization of impurities (Mg, Na, Zn, As) with low boiling points, leaving antimony in the residue, followed by the retention of impurities (Fe, Si, Pb, Bi, Mn, Cu, Al, Au) with high boiling points in the residue. The feasibility of separating antimony from other impurities was analyzed using the theory of vacuum distillation, including saturation vapor pressure, molecular free path, and maximum volatilization rate. In the first step of vacuum distillation at 50 Pa and 630 ℃ for 60 min, zinc, sodium, and magnesium were volatilized to the gas phase, and their content were reduced to 0.17 ppm, 0.14 ppm, 0.13 ppm respectively, which meet the 5 N antimony standard. The content of arsenic was reduced to 1.21 ppm, while the antimony remains in the residue. In the second step of vacuum distillation at 1–10 Pa and 655 ℃ for 30 min, iron, lead, bismuth, manganese, copper, aluminum and gold were significantly reduced to 0.36 ppm, 0.35 ppm, 1.93 ppm, 0.05 ppm, 0.05 ppm, 0.12 ppm and 0.05 ppm, respectively, which meet the 5 N antimony standard, Therefore, the purity of volatile antimony obtained in the second step is 4 N8(99.998 wt%). This method provides reference for the preparation of high purity antimony.