Sustainable Mining and Metallurgy

The arsenic-fixing process of waste acid in a foreign copper pyrometallurgical plant was adjusted from neutralization arsenic-fixing process to crystalline iron arsenate arsenic-fixing process. After adjustment, the arsenic-fixing liquid reached the discharge standard, and the leaching toxicity of arsenic-fixing slag met the TCLP requirements. In order to solve the problem of a large amount of neutralization slag hazardous waste left over from the previous treatment of waste acid by neutralization precipitation method, combined with the process of solid arsenic treatment of waste acid by crystalline iron arsenate after on-site production adjustment, the test of synergistic waste acid treatment of neutral slag hazardous waste was carried out. The alkaline substances such as CaO in the stored gypsum slag hazardous waste were used as neutralizers in the pre-neutralization process of arsenic fixation of waste acid. The test results show that with the increase of the amount of gypsum slag added in the field storage, the available alkaline substances increase, and the amount of limestone powder decreases accordingly. The unstable arsenate precipitation and alkaline heavy metal precipitation in the neutralized slag were dissolved by the waste acid. Therefore, the concentrations of As, Cu, Ni, Pb, Zn, F, Fe, Cd and Sb in the pre-neutralized solution were significantly increased, and the purity of the pre-neutralized gypsum slag was improved, and the toxicity leaching of the pre-neutralized gypsum slag met the TCLP requirements. The process converts gypsum slag hazardous waste into gypsum slag products that meet the external sales standards, realizes “treating waste with waste” and “turning waste into treasure”, and has good economic and social benefits.