Preparation of Ferrous Sulfide–Coal Gangue Composite Material and Experimental Study on Removal of Cr(VI), Cu(II), and Cd(II) in AMD

Given the environmental challenges posed by the treatment of Cr(VI), Cu(II), and Cd(II) in acid mine drainage (AMD). Based on the adsorption characteristics of coal gangue and the high reactivity of nano-FeS, a new type of ferrous sulfide/coal gangue composite (CG-FeS) was prepared by ultrasonic precipitation method. The preparation conditions of CG-FeS were optimized by single-factor and response surface experiments, and the microscopic analysis was carried out by XRD, SEM, TEM, and FTIR. Dynamic column experiments evaluated the removal efficiency of Cr(VI), Cu(II), and Cd(II) by CG-FeS and its ability to adjust pH. The results showed that (1) based on single-factor experiment and response surface experiment, the optimal preparation conditions of CG-FeS were obtained: the particle size of coal gangue was 0.106–0.125 mm, the solid-liquid ratio of CG / S 2 − was 5 / 200 g · mL − 1 , and the concentration of FeSO 4 was 0.53 mol / L . Under optimal conditions, the removal rates of CG-FeS were 94.22%, 81.72%, and 70.33%. Microscopic analysis shows that the strip nano-FeS is evenly distributed on the surface and pores of coal gangue, and the two form a stable composite structure. (2) The dynamic experimental results show that the average removal rates of CG-FeS are 21.18%, 18.90%, and 14.36% higher than those of coal gangue columns, respectively. The results show that CG-FeS can be used as a low-cost adsorbent for the treatment of heavy metal ions in AMD, which provides a new technical reference for the large-scale treatment of AMD and the comprehensive utilization of coal gangue.