Dissolution behavior of hematite in H2SO4 solution: A kinetic analysis and its importance on the zinc hydrometallurgical hematite process

Here, the effect of H2SO4 concentration, temperature, liquid to solid ratio and particle size on the dissolution behavior of industrial hematite in H2SO4 solution. Among them, temperature and H2SO4 concentration have significant effects on the dissolution efficiency of Fe from industrial hematite. Below 363.15 K, the dissolution efficiency of Fe increases with the increase of temperature, but the opposite is true above 363.15 K. Increase H2SO4 concentration to promote the dissolution of industrial hematite. Liquid-solid ratio and particle size had little effect on the Fe concentration after dissolving at 180 min, but it has a significant influence on the Fe dissolution efficiency. The Fe dissolution efficiency of hematite with large particle size is significantly higher than that with small. Shrinking core model with inert reactant layer was employed to describe the dissolving kinetics of industrial hematite in H2SO4 solution. In the temperature range of 303.15 - 343.15 K, the interfacial chemical reaction control is the rate-limiting step. Apparent activation energy (Ea) is 48.1 kJ & sdot;mol- 1. Based on this, four methods were recommended to prevent the re-dissolution of hematite in industrial practice: (1) increasing the reaction temperature, (2) extending the residence time of hematite in high temperature autoclave, (3) reducing the acidity of the slurry in autoclave though add neutralizer, (4) separating immediately hematite from slurry discharged from the autoclave. This work is of great practical value in terms of iron removal and recycle from the ZnSO4 solution though the hematite process with efficient, clean and low temperature at 423.15 K.