China Nonferrous Metallurgy

The copper anode slime and the acidic slime from Pb-Zn smelter are the main source for Se resources recycling, the current commonly used pyrometallurgical and hydrometallurgical recovery processes have the disadvantages of incomplete separation of Se and Hg or high cost for slag/residue treatment. In this article, the acidic Se-Hg slime of a lead refinery is used as raw material to conduct a Se-Hg separation test by means of POX alkaline leaching, with the following results: under the conditions of alkaline use being 1.2 times of acidic slime (dry basis), oxygen pressure being 2.0MPa, temperature being 180℃, liquid-solid ratio being 3∶1 and reaction time being 2.5 hours, the Se leaching efficiency is as high as 99% or more and the Hg slag solidification efficiency is 98% or more. And 98% crude Se can be obtained by purification, impurity removal and reduction of the alkaline leaching liquid. This technology can be used to safely and effectively separate Se and Hg in acidic slime, the neutralized residue can be subject to dilute acid leaching and returned to Pb system for Pb recovery and the sulfurized residue can be returned to the POX alkaline leaching system for Se recovery adding to the total Se recovery. In addition, in this method, the elemental Hg in the acidic slime is converted into Hg oxide that is not volatile under normal temperature, avoiding pollution of Hg during storage and transport.