Selective separation of Al, Fe, and Ti from red mud leachate by Fe-Ti iso precipitate flotation and reduction hydrolysis process: Ions selective chelation and separation mechanism

Abstract

Bauxite residue (red mud) is a typical solid waste discharged from the aluminum metallurgy industry and can be considered as an alternative resource for the recovery of iron (Fe), aluminum (Al), and titanium (Ti). Acid leaching is an effective technique for the simultaneous extraction of valuable metals from red mud, whereas the leachate with various metals confronts the difficulty of metals separation. In this work, a selective separation and recovery of Fe, Al and Ti from red mud leachate by the preferential Fe-Ti iso precipitate flotation followed by a reduction-hydrolyzation process was proposed. In the iso precipitate flotation process, the cupferron was acted as an Fe-Ti synchronous chelation agent and hexadecyl trimethyl ammonium bromide (CTAB) was used as an anionic collector for the flotation separation of Fe-Ti chelate. The generated fine hydrophobic chelates are rapidly separated from solution by flotation with the assistance of CTAB, in which 99.3% Fe and 99.8% Ti were transferred into the flotation product, while 96.7% Al remained in the leachate, realizing the first separation of Al. Reduction-hydrolyzation was further conducted to separate Ti and Fe from the dissolving solution of the flotation product. Hydrolysis thermodynamic analysis indicated that the required hydrolysis pH range of Fe2+ was much different from that of TiO2+ and Ti3+. After selective reduction of Fe3+ to Fe2+ by KI, 99.8% Ti was concentrated in the residue while 94.8% Fe remained in the solution. Eventually, the comprehensive recoveries of Fe, Ti, and Al are 94.1%, 99.7%, and 96.7%, respectively.