A Salty Treat: Extracting High-Quality Magnesium Sulphate from Seawater Desalination Brine

Researchers develop novel method to extract high-quality magnesium sulphate, without calcium impurities, from seawater

The world’s need for high quality mineral ores can no longer be met by mining alone, thus calling for alternatives. Accordingly, Korean researchers have achieved success in extracting high quality magnesium sulphate, devoid of the commonly found calcium impurities, through a novel ethanol-based method from readily available seawater desalination brine, according to a study published in Desalination.

Given that mining to extract high-grade mineral ores is wastefully energy intensive, exhaustible, and bad for the environment, scientists have been scouting for alternatives. A group of Korean researchers, led by Professor Myoung-Jin Kim, from Korea Maritime and Ocean University, have now succeeded in extracting high-quality minerals from just seawater. Specifically, they have achieved the extraction of 99.8% pure magnesium sulphate (MgSO₄), from seawater desalination brine (SDB).

Speaking about the motivation behind the study, Prof. Kim exclaims, “Since we have already developed a sophisticated seawater desalination process to address the world’s water needs, why not couple it with the beneficial process of mineral extraction! In this way, we believe that such extraction can be performed in an energy-efficient, sustainable, and environment-friendly manner.” The team’s findings have been published online, as a research article on 8^th August 2021, in Volume 518 of the journal, Desalination.

Further, the team has not only coupled the two processes, but has also developed a novel and subtle ethanol-based process to extract MgSO₄. Initially, the researchers followed steps such as alkali-based magnesium hydroxide pre-precipitation from brine, and sulfuric acid-based magnesium concentration. Finally, they treated the magnesium eluate, twice, with ethanol―the first time, to remove calcium impurities, and the second time, to precipitate the high-purity MgSO₄. Interestingly, this final two-step process used the difference in solubility between magnesium and calcium sulphates in ethanol, to achieve up to 67% magnesium recovery efficiency.

Owing to the cost-effectiveness of mineral extraction from SDB, the researchers state that the obtained MgSO₄ may not only be used for re-mineralizing desalinated fresh water, but also find potential applications in the pharmaceutical and food industry. Prof. Kim adds, “We hope that our study encourages further research on alternative mineral extraction processes.”

Indeed, humanity, with the aid of such science, can hope to reverse environmental damage, while sustainably meeting its needs for continued technological advancements.

DOI: https://doi.org/10.1016/j.desal.2021.115288

*Corresponding author’s email: kimmj@kmou.ac.kr

About Dr. Myoung-Jin Kim

Dr. Myoung-Jin Kim is a Professor of Environmental Engineering at the Korea Maritime and Ocean University. Professor Kim’ is interested in developing technologies to store carbon dioxide and produce calcium carbonate through indirect carbonation; and economically recovering high-purity magnesium compounds from seawater. She received her PhD in Environmental Health Sciences from the University of Michigan, USA, in 1999. She has authored more than 35 research publications, in internationally reputed journals.