Reduction of Bauxite through Hydrogen: Future Method of Extraction of Aluminium

Abstract

The present investigation aims at beneficiating the run of the mined bauxite mineral for enhancing the purity of alumina which can be subsequently treated for aluminium extraction. The gangue constituents are to be reduced considerably to put in pace, a process for alumina extraction which can be accompanied at relatively lower cost with minimum affects on the ambience. Looking into the demerits of Bayer’s process, the age old process for alumina beneficiation, the present process involves reduction of the bauxite mineral by molecular hydrogen, microwave assisted hydrogen plasma and hydrogen plasma smelting. The material after reduction subjected to leaching or magnetic separation with different magnetic field intensities. The products are characterized through chemical composition, XRD (X-ray Diffraction) analysis, XRF (X-ray Fluorescence Spectroscopy) analysis, thermal analysis, microscopic analysis (Optical & SEM (Scanning Electron Microscopy)) and FTIR (Fourier Transform Infrared Spectroscopy) analysis. The results revealed that thermal hydrogen plasma reduction yielded the best figures concerning alumina yield which could be further treated for aluminium extraction. On the other hand the magnetic separation yielded an iron rich segment which can be considered for iron extraction. The magnetic separation is most effective at a magnetic field intensity of 14500 Gauss. Further, as revealed from chemical composition and XRD analysis, the non-magnetic portion after magnetic separation consisted of 88.67 % of alumina whereas the magnetic portion exhibited considerable enrichment of iron bearing constituents to the extent of 90 %. It was also observed that different conditions of hydrogen processing of the run of the mined bauxite mineral used in the present study could reduce only the iron oxide present in the bauxite mineral. However, the alumina obtained through hydrogen plasma processing followed by magnetic separation when subjected to hydrogen plasma smelting for hydrogen flow rate of 10 litres per minute for 25 minutes produced aluminium of 84.16 % purity. Acid leaching of the run of mined bauxite showed that more than 96 % of iron constituents can be removed from the raw bauxite with HCl concentration of 3 M at temperature of 90 oC.