Recovery of Fe and Al from red mud by a novel fractional precipitation process

The development of cheap and effective approach for utilizing red mud (RM) waste is a long and arduous task. This work provided a technically and economically feasible route to utilize RM waste for the production of high valuable chemicals by use of the industrial wastes as cheap raw materials. The Fe and Al elements were first leached from RM through hydrothermal reaction and then were separated by precipitation after the Fe(III) in leachate was reduced to Fe(II) by iron powder. Above 90% Fe and Al were extracted from RM with the Fe and Al purity of about 95% and 45%, respectively. The control test revealed that the main impurity of Al product was caused by the adsorbed SO₄^2- during the precipitation of the Al³⁺. The structural characterization demonstrated that the obtained Fe products were in nanoscale, and the Ti-Si residue has high BET area of 203.7 m²/g. Four products of nano-Fe₃O₄/nano-Fe, aluminum oxide, Ti-Si residue, and (NH₄)₂SO₄ were obtained as valuable chemical materials for industry. This demonstrated utilization of industrial waste to produce high added-value products with high efficiency and low cost will possess promising application prospect for the resource utilization of RM in industry.