Purification of cadmium by vacuum distillation and its analysis

摘要

High purity (99.9999 percent or 6N) cadmium (Cd) was obtained through multiple vacuum distillation using 99.98 percent (3N8) pure Cd as input material and condensing the vapours of the distillate on a high-density graphite collector. The soaking temperature and the time were optimized to achieve the desired purity and distillation rate/yield at a dynamic vacuum level of approx 2.1 X 10~(3-) Torr. The detailed analysis of input as well as purified Cd was carried out by inductively coupled plasma optical emission spectrometry (ICP-OES) for 29 major impurity elements. The analysis confirmed the reduction of total impurity content from approx 190 to approx 1.8 ppm (approx 6N) upon three consecutive vacuum distillations. The present studies showed that the major impurities separated from the distilled cadmium are Zn, Cu, Ag, Sb, Pb, Bi, Fe, Ni, TI, etc. It was observed that these impurities require adaptation of elemental analyzing technique to counter dilution effect.