Removal of impurities from crude lead with high impurities by vacuum distillation and its analysis

• The purity over 99% of lead has been obtained by a two-stage vacuum distillation.
• Cu, Sn, Ag and partial Sb can be removed at the high temperature distillation.
• Zn and As can be removed at the second stage of low temperature distillation.
• The calculated results can fill the inadequate of the thermodynamics.

A novel technology was developed to remove impurities from crude lead with high impurities by vacuum distillation. Refined lead (purity over 99%) was achieved through vacuum distillation using crude lead (92.88%) with high impurities as input material under a dynamic vacuum of 5–15 Pa. The results show that vacuum distillation should be taken to obtain lead from crude lead matrix, in which low-volatile impurities namely Cu, Sn, Ag and partial Sb are concentrated in residue at the first fraction stage of 1373 K. Volatilized lead containing high-volatile impurities such as Zn and As is distilled to remove these impurities at the second fraction stage of 973 K. But the property of impurity Bi is similar to lead that can not be separated from crude lead. The separation coefficient (βi) and the activity coefficient (γi) of impurity elements are calculated according to the experiments to fill the inadequate data of the thermodynamics.