Sustainable Mining and Metallurgy

A lead smelter adopts lime-iron salt method to treat waste acid wastewater, but there are some problems, such as unstable operation, difficulty in reaching the standard of water quality, high risk of thallium pollution and high cost of slag treatment. In order to solve the above problems, this paper used the process of “sulfidation + one-stage neutralization + two-stage deep neutralization” to optimize the treatment process of waste acid wastewater. The feasibility of the vulcanization method was verified on the basis of comparing the vulcanization agents, analyzing the subsequent process and analyzing the properties of the slag. Using this process, the removal rate of arsenic and thallium in the vulcanization stage reached more than 99%, and by controlling the pH value of the end point of the reaction to be 2.5-3.0, the content of heavy metals in the gypsum slag was less than 0.05%, and the quality of gypsum slag could be effectively guaranteed. The process of neutralization + iron salt + deep oxidation/vulcanization was adopted in the second stage of neutralization and deep treatment. By controlling the pH value of the reaction end point at 7.5-8.5, and the heavy metal content of the final effluent could reach the standard. The process produced three kinds of slag, most of the heavy metal pollutants were removed in the form of sulfide precipitation by vulcanization. The sulfide slag was a hazardous waste containing thallium ; the gypsum residue produced by neutralization of a section of gypsum was general hazardous waste; the content of thallium in the neutralization slag produced by the second stage neutralization was less than 20g/t, which belonged to hazardous waste. All three kinds of slag have disposal destinations. By changing the nature of the slag and returning to the furnace for disposal, more than 65% of the hazardous waste slag can be reduced.