Selective reduce roasting–magnetic separation towards efficient and cleaning removal of iron values from bauxite residual

Abstract

ABSTRACTThe recycling application of bauxite residual is limited by its high content of iron, unfortunately, the complicated embedding feature of haematite makes it quite difficult to be removed efficiently and cleanly. In this paper, the process of selective reducing-magnetic separation without acid leaching is adopted to remove iron from bauxite residual. Different parameters such as carbon mass addition, roasting temperature, reduction time, magnetic field intensity and grain size on the iron removing ratio and iron yield are systemically investigated. It is indicated that haematite in bauxite residual is reduced to magnetite basically after 700°C roasting for 2.5 h by 1.0 wt-% carbon powder reducing, and the optimal conditions of magnetic separation are magnetic intensity of 235 mT and grain size of +150 μm, respectively. After selective reduce roasting–magnetic separation, iron content in the bauxite residual is sharply decreased from 7.98 to 1.34%, the iron removal ratio is 83.21%, and iron-rich magnetic concentrate contains about 30.48% iron, meanwhile, 87.03% of the iron in bauxite residual is enriched in the magnetic concentrate. The process is characterised by efficient and clean removal composite iron impurities from bauxite residual without using acid leaching.