KINETIC STUDY ON THE REMOVAL OF LEAD AND SILVER FROM CRUDE BISMUTH BY ANODE REFINING
Zhang Yongjian; Ren Hongyan;Xie Zhong(Department of Non-Ferrous Metallurgy, Central South University of Technology, Changsha, 410083, China)
The anode refining process to remove lead and silver from crude bismuth was studied. The study was carried out with chloride melts at 400 ℃ in a crucible-in-crucible type pyrex glass electrolyzer. The kinetic regularity of the removal of lead and silver was found to be in accordance with the equation:Inc=b-kt. Values of constant k were determined for different current density.The relationship between the purity of refined bismuth and its direct yield wasalso determined. A two-stage anode refining method was established. The firststage. was to remove most part of lead (about 90%) at higher current density ;the second stage was used for removing silver and the remains of lead at lowercurrent density. Under appropriate conditions high purity (WPb 0.001%,WAd0.004%) of bismuth could be obtained from crude bismuth with the direct yield of bismuth up to 98%.