<Original Papers>Separation of Impurities from Zinc Concentrates by Volatilization in Nitrogen Atmosphere

Volatilization behavior of various sulfides accompanied with zinc concentrate was first estimated from the data of vapor pressure of respective sulfides. Based on the tendency estimated, the experiments were carried out for the actual concentrates by heating them under a constant flow of nitrogen in order to find a possibility of purification of zinc concentrate. Experimental results obtained agreed well with the trend estimated from the data of vapor pressure. Zinc content in concentrates slightly increased with increasing temperature, due to the lower vapor pressure of zinc sulfide than the others, in the range of experimental temperatures. The rate of vaporization of cadmium sulfide was not higher than that of lead sulfide, but, the complete removal of these sulfides were attained when they heated up to about 1,100℃. Bismuth was easily removed, but the removal of indium and silver were not so easy, compared with the former. In spite of comparatively high vapor pressures, the elimination of tin and antimony was not so easy. This phenomenon may be explained by the formation of solid solutions with zinc sulfide. This process may be used as a simple industrial method for the removal of impurities or recovery of some valuable metals from zinc concentrate, especially the production of low lead zinc and the recovery of germanium, cadmium, etc