Process for separation and recovery of metal values from sulfide ore

Abstract

An improvement in conventional processes for recovering metal values from sulfide ores containing lead, zinc and silver sulfides in which process the metal sulfides are converted to chlorides by chlorination followed by solubilization of the chlorides with a sodium chloride leach and subsequent recovery of the metals from their chlorides in accordance with a conventional flow sheet including crystallization, cementation, precipitation, fused salt electrolysis, etc., with chlorine being recovered for reuse by electrolysis of the sodium chloride leach solution substantially depleted of lead, silver and zinc, the improvement being a pollution-free process which comprises: 1. recycling the sodium chloride solution depleted of a major percentage of lead and silver to the sodium chloride or brine leaching step; and 2. controlling the concentration of zinc and other impurities in the sodium chloride or brine leaching solution by bleeding a portion from the recycle stream of (1) above, removing lead, zinc and other metal impurities from the bleed stream, electrolyzing the bleed stream to produce chlorine, sodium hydroxide and a weak sodium chloride solution followed by recycle of the chlorine to the dry chlorination step and weak sodium chloride solution, after concentration, to the leach solution to control the concentration of zinc chloride and other impurities in the leach solution. A further improvement is the use of an alternate dry chlorination procedure for the sulfide ores and, particularly, ores such as the tetrahedrite-tennantite series which are more satisfactorily chloridized by dry chlorination than by wet chlorination. Another improvement is use of a flow sheet by which no impurities are removed from the process in the form of chlorides so that no chlorine is lost from the system.