Sustainable Mining and Metallurgy

Aiming at the problem that the amount of gypsum residue produced by the treatment of contaminated acid by lime neutralization method in zinc hydrometallurgy is large, this paper proposed a process of using zinc calcine-calcium carbonate two-stage neutralizations method to treat the liquid after vulcanization. The process neutralizes part of the acid by zinc calcine and then neutralizes it by calcium carbonate, which removes fluorine and reduces the production of waste acid gypsum residue. When zinc calcine is used for neutralization, the pH value is controlled to be 2.0~2.5, and the neutralization is carried out at 35℃ for 1h. After sedimentation and filtration, calcium carbonate is used for the second stage neutralization. The end point pH is controlled to be 5.0~5.5, and the reaction time is 1h. Under these conditions, the fluorine content of the solution after fluorine precipitation is less than 20mg/L, and the fluorine precipitation rate is more than 98%. The output gypsum slag is only 24.94% of the gypsum slag produced by the traditional lime neutralization method. The solution can be returned to the wet system after subsequent dechlorination.