Microwave digestion of gibbsite and bauxite in sodium hydroxide

Dillinger, Ben; Batchelor, Andrew; Katrib, Juliano; Dodds, Chris; Suchicital, Carlos; Kingman, Sam; Clark, David

Abstract

It was hypothesized that bauxite digestion may be improved by using microwave heating as it has been shown in literature that some material processes have improved efficiency. To test this hypothesis, a set of digestion experiments were conducted using gibbsite, one of the major minerals in bauxite. Gibbsite was digested at various temperatures (50, 75, and 95 °C) in either 1 M or 6 M sodium hydroxide solutions for 30 min using either a convection oven or a 2.45 GHz microwave applicator. Results show that microwave heating provided an increase of 5–7% in the digestion after 30 min and required around 1/10th the time to heat the solutions compared to conventional heating. Electromagnetic simulations show that preferential heating occurs at the solution surface creating a temperature gradient within the solution. Although vigorous stirring of the solution was used to minimize the temperature gradient, it could still be responsible for the observed difference in digestion. Digestion of bauxite itself yielded similar results to the gibbsite.

Citation

Dillinger, B., Batchelor, A., Katrib, J., Dodds, C., Suchicital, C., Kingman, S., & Clark, D. (2020). Microwave digestion of gibbsite and bauxite in sodium hydroxide. Hydrometallurgy, 192, Article 105257. https://doi.org/10.1016/j.hydromet.2020.105257

• Journal Article Type: Article
• Acceptance Date: Jan 14, 2020
• Online Publication Date: Jan 21, 2020
• Publication Date: 2020-03
• Deposit Date: Feb 20, 2020
• Publicly Available Date: Jan 22, 2021
• Journal: Hydrometallurgy
• Print ISSN: 0304-386X
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 192
• Article Number: 105257
• DOI: https://doi.org/10.1016/j.hydromet.2020.105257
• Keywords: Microwave heating; Microwave simulation; Mineral digestion; Bayer process; Gibbsite
• Public URL: https://nottingham-repository.worktribe.com/output/3788041
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S0304386X19308412?via%3Dihub