Development of barium@alginate adsorbents for sulfate removal in lithium refining
- PDF / 1,736,545 Bytes
- 10 Pages / 595.276 x 785.197 pts Page_size
- 106 Downloads / 166 Views
RESEARCH ARTICLE
Development of barium@alginate adsorbents for sulfate removal in lithium refining Lisa Xu, Kaifei Chen, George Q. Chen, Sandra E. Kentish, Gang (Kevin) Li (✉) Department of Chemical Engineering, The University of Melbourne, Parkville, VIC 3010, Australia
© Higher Education Press 2020
Abstract The demand for lithium has been steadily growing in recent years due to the boom of electric cars. High purity lithium is commonly used in the manufacture of battery grade lithium electrolyte. Sulfate residuals originating from acid leaching of lithium ores must be limited to below 20 mg$L–1 during refining. There are methods to remove sulfate such as membrane processing and chemical precipitation using barium salts. However, membrane separation is unable to achieve the required purity while chemical precipitation often causes secondary contamination with barium and requires extra filtration processes that lead to increased processing costs. In this study, we developed a polymeric matrix entrapped with barium ions as a novel adsorbent to selectively adsorb sulfate in aqueous solutions. The adsorbent was prepared by dropwise injection method where alginate droplets were crosslinked with barium to form hydrogel microcapsules. In a typical scenario, the microcapsules had a diameter of 3 mm and contained 5 wt-% alginate. The microcapsules could successfully reduce sulfate concentration in a solution from 100 to 16 mg$L–1, exceeding the removal target. However, the microcapsules were mechanically unstable in the presence of an excess amount of sulfate. Hence, calcium ions were added as a secondary crosslinking agent to improve the integrity of the microcapsules. The two-step Ca/Ba@alginate microcapsules showed an exceptional adsorption performance, reducing the sulfate concentration to as low as 0.02 mg$L–1. Since the sulfate selective microcapsules can be easily removed from the aqueous system and do not result in secondary barium contamination, these Ca/Ba@alginate adsorbents will find applications in ultra-refining of lithium in industry. Keywords barium@alginate, microcapsules, dropwise injection, sulfate removal, lithium
Received February 3, 2020; accepted June 5, 2020 E-mail: [email protected]
1
Introduction
The demand for lithium-ion batteries has grown with the popularity of electric cars and mobile devices [1]. The cathode of lithium-ion batteries uses lithium metal oxide, which is made from lithium compounds extracted from lithium deposits, such as high purity lithium hydroxide or lithium carbonate. Apart from brines, rock deposits are the most common form of lithium particularly in Australia, Canada, and China [2]. The conventional way to extract lithium from pegmatite containing spodumene [3] includes calcination at above 1050 °C to loosen the lattice to form b-spodumene, followed by leaching with concentrated sulfuric acid [4] to extract the lithium. The leaching process results in a lithium sulfate concentrate. This is then purified and reacted with sodium carbonate or calcium hydroxide to produce
Data Loading...
