Abstract
To develop technology to help assure an ample domestic supply of zinc, the Bureau of Mines is investigating an aqueous chlorine- oxygen leaching process for treating complex sulfide concentrates. This report discusses the purification of aqueous cl2-o2 leaching solutions by utilizing zinc cementation to remove cd, CO, cu, ni, and pb. Additional processing of the purified solution is necessary to produce zncl2 crystals suitable for molten-salt zinc electrowinning cells. The effects of solution temperature, reaction time, zinc dust concentration, zncl2 concentration, and degree of agitation on the removal of impurities were investigated for both simulated and actual leaching solutions. Zinc dust addition to a leaching solution at 30 deg c decreased the cd, cu, ni, and pb concentrations to acceptable levels of less than 3 mg/l each. By increasing the solution temperature to 75 deg c, the cobalt content was decreased to less than 5 m/gl, an acceptable level for producing electrolytic cell-grade zncl2. Impurity removal rates from zncl2 solutions are pb>cu=cd>ni>>co. An increase in the solution temperature increases the rate of removal for these metal impurities.
