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Method for recovering anhydrous ZnCl2 from aqueous solutions.
Eichbaum BR; Schultze LE
Sep Sci Technol 1993 Jan; 28(1-3):693-717
To develop technology to assure an ample supply of zinc and to reduce environmental pollution, the U.S. Bureau of Mines investigated alternatives to the roast-leach process for treating complex sulfide concentrates. Previous studies proved that low-grade zinc sulfide (ZnS) concentrates could be leached using chlorine-oxygen to produce zinc chloride (ZnCl2). The process involves high energy requirements for evaporating the pregnant solution to produce anhydrous ZnCl2 needed for electrolytic cell feed. An efficient hydrometallurgical process would facilitate treatment of lower grade ores that can be used in conventional processing and would render roasting unnecessary. It is difficult to keep ZnCl2 anhydrous as it is hygroscopic and deliquescent. Therefore, an alternate method of producing a feed material from solution, which could be stored without absorbing H2O, was sought. Zinc diamine chloride [Zn (NH3)2Cl2], was precipitated from solution by adding ammonium chloride (NH4Cl) and sparging with ammonia (NH3) to a pH of 6 to 7.5. The spent solution was treated with calcium hydroxide [Ca (OH)2] at 60 degrees to 80 degrees C for 1 to 4 h to remove remaining zinc and NH3. The Zn (NH3)2Cl2 was heated to 300 degrees to 400 degrees C to remove NH3 and produce anhydrous ZnCl2. A possible flowsheet was devised and will be presented.
Zinc compounds; Zinc; Metallurgical processes; Metallurgy; Metals; Environmental impacts; Environmental protection
Issue of Publication
Separation Science and Technology
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division