Abstract
To tackle the challenge of bauxite residue (BR), generated during the alumina production, as well as to recover some of its metal content, three combinatory H2-based processes were utilized. Firstly, Greek BR was mixed with NaOH to produce water soluble Na-aluminates and was roasted under pure H2 gas in order to reduce the Fe+3 content. Then the first process combined water leaching and magnetic separation, the second water leaching and melting and the last included wet magnetic separation. The water media resulted in the dissolution of Na-aluminate phases and the production of Al, Na-ion rich leachates. From these, pregnant leaching solutions recovery of Al was 78%, 84% and for the third case it reached 91%. Concerning Na recovery, it could reach 94%. Both melting process and magnetic separation aimed for Fe recovery from the material. The former case however still needs to be optimized, here its concept is introduced. The magnetic fraction, after the dry magnetic separation, varied in Fe content from 31.57 wt.% to 38.50 wt.%, while after the wet magnetic separation it reached 31.85 wt.%.
Highlights
Many efforts and researches have been conducted on the valorization of bauxite residue (BR), with the most successful—concerning industrial application—being in clinker production, in road construction and in iron/steel production
The process that will deal with the BR challenge should engage the main obstacles of its smooth utilization—quality diversity, complex mineralogy and logistics [1,2]—and counter them
The presented combinatory processes attempt to deal with the BR storage capacity while being greener and employing the latest trends in industry, utilizing the capabilities of H2 gas [3,4]
Summary
Many efforts and researches have been conducted on the valorization of bauxite residue (BR), with the most successful—concerning industrial application—being in clinker production, in road construction and in iron/steel production. With technology evolving rapidly a novel process should follow the trends and directions in industry, and be, as eco-friendly as possible To this direction, lower temperature and less polluting agents should be applied. The presented combinatory processes attempt to deal with the BR storage capacity while being greener and employing the latest trends in industry, utilizing the capabilities of H2 gas [3,4]. Recovery of both Al and Fe combined through one process, is more cost-effective [5]. Proc. 2021, 5, 45 combination with H2 gas, which is effective at lower temperature (
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