セキム海水からマグネシウム塩を採取するフローベースの新手法 A new flow-based method harvests a magnesium salt from Sequim seawater
2022-09-23 アメリカ・パシフィック・ノースウェスト国立研究所(PNNL)
20世紀半ば、制酸剤「マグネシアミルク」の名前の由来となった水酸化マグネシウム塩を加工して、金属マグネシウムを作ることに成功したが、この工程では、マグネシウム塩とカルシウム塩が複雑に混ざり合い、分離が困難でコストがかかる。今回の研究では、純粋なマグネシウム塩が得られるため、より効率的な加工が可能になった。
＜関連情報＞
- https://www.pnnl.gov/news-media/simple-process-extracts-valuable-magnesium-salt-seawater
- https://pubs.acs.org/doi/10.1021/acs.estlett.2c00229
海水からのフローアシストによる選択的鉱物抽出 Flow-Assisted Selective Mineral Extraction from Seawater
Qingpu Wang, Elias Nakouzi, Elisabeth A. Ryan, and Chinmayee V. Subban
Environmental Science & Technology Letters Published:May 31, 2022
DOI:https://doi.org/10.1021/acs.estlett.2c00229
Abstract
The sustainable production of critical materials from natural sources requires a paradigm shift away from currently used resource-intensive processes. We report a single-step, laminar coflow method (LCM) that leverages nonequilibrium conditions to selectively extract pure Mg(OH)2 from natural seawater. Conventional seawater-based Mg extraction involves adding individual or a combination of precipitants to obtain Mg(OH)2, but the coexistence of Ca2+ unavoidably results in CaCO3 impurities requiring additional purification steps. Here, we show that the nonequilibrium conditions in LCM achieved using a microfluidics device and by simply coinjecting a NaOH solution with seawater can result in improved selectivity for Mg(OH)2 unlike in a conventional bulk mixing method. The resulting precipitates are characterized for composition, and the process yield and purity are optimized through systematic variations of the reaction time and the concentration of NaOH. This is the first demonstration of LCM for selective separation, and as a one-step process that does not rely on novel sorbents, membranes, or external stimuli, it is easy to scale up. LCM has the potential to be broadly relevant to selective separations from complex feed streams and diverse chemistries, enabling more sustainable materials extraction and processing.
