Removal of barium impurities from selenium by vacuum distillation

Abstract

We have studied the behavior of barium impurities in the form of BaF2 and BaO during vacuum distillation of selenium. The effective Ba partition coefficient is shown to depend on the impurity concentration and evaporation rate. At initial barium contents in the range 3 × 10−3 to 2 × 10−5 wt %, the effective Ba partition coefficient is 600 and 1.5 at distillation rates of 4.7 × 10−6 and 1.5 × 10−3 cm3/(cm2 s), respectively. The chemical form of barium has no significant effect on its partition coefficient. Using a Rayleigh distillation equation, we have determined the equilibrium partition coefficient and the thickness of the diffusion boundary layer in the system.