Abstract:In order to reveal the influence of species distribution of Fe3+ in the leachate on the leaching effect of hematite in roasting cyanide tailings, the leaching effects of H2C2O4, H2C2O4-H2SO4 and H2C2O4-K2C2O4 on hematite were studied. Response Surface Method (RSM) was used to optimize the leaching process of hematite with H2C2O4 and K2C2O4. The results show that the species distribution of Fe3+ affects the leaching effect of hematite, when H2C2O4 and K2C2O4 were used as iron removal agents, n(H2C2O4)/n(K2C2O4) mole rate, the excess multiple of (C2O42-)T, and temperature affect leaching pH value and c(C2O42-)T, and they should be sufficient for Fe3+ conversion to form Fe(C2O4)33-. Fe3+ exists only in form of Fe(C2O4)33-, the leaching time of hematite can be shortened and the leaching rate of iron can be improved. The iron removal optimization conditions with H2C2O4 and K2C2O4 are as follows: n(H2C2O4)/n(K2C2O4)=1.03, (C2O42-)T dosage of 1.37 times of the theoretical amount, 94 ℃, L/S=5 mL/g, and 30 min. Under the optimal conditions, the actual and predicted values are 98.42% and 97.73% respectively, and the relative error is 0.69 percentage point. The effect of the factors on iron removal is sorted as (C2O42-)T excess ratio, leaching temperature, and n(H2C2O4)/n(K2C2O4). Among them, the interaction between n(H2C2O4)/n(K2C2O4) and leaching temperature is the most significant. The results of H2C2O4-K2C2O4 leaching hematite from the roasting cyanide tailings further prove that the oxalic acid - oxalate leaching system is an efficient iron removal agent. Moreover, the process of iron resource utilization in the leaching solution is simple, and its advantages are incomparable to the existing iron removal agents.