Selective Liberation of High-Phosphorous Oolitic Hematite Assisted by Microwave Processing and Acid Leaching

Abstract

The release of valuable minerals from the associated gangues is called liberation. Good liberation is essential to the subsequent separation stage. Selective liberation is advantageous to improve the degree of liberation. Oolitic hematite is one of the typical refractory iron ores in China, and its resources are abundant. However, owing to its fine dissemination and complex mineralogical texture, the conventional grinding processes are inefficient in improving the selective liberation of oolitic hematite. In this study, microwave processing and acid leaching were used to assist the liberation of oolitic hematite. The assisted liberation of the oolitic hematite mechanisms of microwave processing and acid leaching were studied by using scanning electron microscope (SEM), X-ray diffraction (XRD), BET specific surface area detection method (BET) and the transflective microscope method. The results indicated that microwave processing can reduce the mechanical strength of oolitic hematite and improve the liberation of hematite, and acid leaching can improve the microwave-assisted liberation efficiency and reduce the content of phosphorus in the grinding product. Compared to direct grinding, the liberation of hematite increased by 54.80% in the grinding product, and especially, the fractions of −0.038-mm and 0.05–0.074 mm increased significantly; however, there was no obvious change in other grain sizes, and the dephosphorization ratio reached 47.20% after microwave processing and acid leaching. After the two stages, the iron grade and recovery of the magnetic separation product increased by 14.26% and 34.62%, respectively, and the dephosphorization ratio reached 88.59%. It is demonstrated that microwave processing and acid leaching comprise an efficient method to improve the liberation of hematite and the dephosphorization ratio of oolitic hematite. The two-stage treatment can achieve selective liberation of oolitic hematite, which is beneficial to the following magnetic separation.

Keywords

• oolitic hematite
• microwave
• acid leaching
• selective liberation
• dephosphorization