Leaching behavior of metals from iron tailings under varying pH and low-molecular-weight organic acids

The migration of metals (e.g., Fe, Cd, Co, Cr, Cu, Mn, Ni, and Zn) in both of iron tailings under different pH leachates was studied by laboratory static leaching experiments. The results indicated that Fe showed the highest leaching concentration at an initial pH of 2, reaching 16.19 and 51.72 mg L^-1 in the Qian'anling (Q0) and Majuanzi (M0) iron tailings, respectively. Metal ions manifested a strong pH dependence. In addition, the leaching behavior of Cd, Cr, Fe, and Cu for the two tailings was also evaluated under leaching by three low-molecular-weight organic acids (LMWOAs). The results indicated the leaching of Cd and Fe followed the order of citric acid > malic acid > oxalic acid and that the leaching order for Cr and Cu was citric acid > oxalic acid > malic acid. The concentration of Fe was low in 5 mM oxalic acid leaching for 20 days because of the hydrolysis precipitation of iron ions and the complexation with organic ligand. The crystal lattice on the tailings was significantly damaged after leaching. The CO₃^2- peak appeared in M0 with different treatments, and the proportion of COO- fitting peak areas increased markedly after leaching with LMWOAs.