Magnesium recovery from seawater desalination brines: a technical review

Abstract

Existing desalination technologies produce large amount of waste brines with higher salinity concentration than feed seawater, the disposal of which pose serious environmental problems. At the same time, waste brines represent a valuable source of strategic materials—such as magnesium—and therefore their valorization offers the opportunity to overtake both the environmental and the economic issues. Current needs are to identify gaps and challenges to recover secondary magnesium in order to bring recovery technologies closer to the market for potential commercial applications. In this technical review, the available methods for magnesium recovery from seawater desalination brines are described and compared in details, to provide the readers with a wide overview to better address their research efforts towards resources valorization, in accordance with the circular economy principles. Graphical abstract

Biomass-Based Ferric Tannate Hydrogel with a Photothermal Conversion Function for Solar Water Evaporation

“…Seawater and brackish water, which occupy the highest proportions in nature, are an available source for desalination to obtain fresh water. 1 To receive water with a lower salt concentration, several technologies have been developed, such as distillation, 2 electrodialysis, 3 ion exchange, 4 reverse osmosis, 5 and so on. Taking advantage of evaporation condensation or ion absorption, high-concentration saline water could be desalinated.…”

“…With the growing population and severe climate change, the shortage of freshwater resources has gradually become one of global urgent issues. Seawater and brackish water, which occupy the highest proportions in nature, are an available source for desalination to obtain fresh water . To receive water with a lower salt concentration, several technologies have been developed, such as distillation, electrodialysis, ion exchange, reverse osmosis, and so on.…”

Evaluation of the Purity of Magnesium Hydroxide Recovered from Saltwork Bitterns

“…As an alternative, the use of low-cost lime (Ca(OH) 2 ) suspensions is also possible and may lead, in principle, to high Mg(OH) 2 purity if suitable brine or seawater pre-treatments are adopted in order to reduce carbonates, calcium, and sulphate ions. In the literature, the following strategies have been reported: (i) the use of highly pure lime suspensions [32]; (ii) decarbonation of brines to avoid calcium carbonate precipitation by adding sulfuric acid (H 2 SO 4 ) to lower the solution pH to four, combined with a carbon dioxide removal step using a desorption tower and a brine aerating process [32]; (iii) a controlled reaction with Ca(OH) 2 to precipitate soluble bicarbonate as insoluble calcium carbonate without Mg(OH) 2 precipitation [32]; and (iv) adoption of sodium carbonate (Na 2 CO 3 ) and barium chloride (BaCl 2 ) solutions to precipitate calcium as calcium carbonate (CaCO 3 ) and sulphates as barium sulphate (BaSO 4 ) [33].…”

Recent Trends and Future Perspectives of the Magnesium Recovery based on Electrolysis

“…마그네슘은 주로 광석이나 염수/해수에서 추출가능하 며, 후자의 경우 침전 및 결정화 등을 통해 마그네슘을 회 수될 수 있다 5) . 이 중 산염기 반응 기반 침전은 현재 염수 내 마그네슘 회수에 보편적으로 적용되는 기술이다 1,5) . 마 그네슘 침전을 위해서 수산화나트륨이나 소석회 등 다양 한 침전제가 사용된다 1) .…”

“…이 중 산염기 반응 기반 침전은 현재 염수 내 마그네슘 회수에 보편적으로 적용되는 기술이다 1,5) . 마 그네슘 침전을 위해서 수산화나트륨이나 소석회 등 다양 한 침전제가 사용된다 1) . 다만 침전은 다량의 약품이 주입 되어야 하며 그에 따른 경제적 비용 및 기술적 부담이 따 른다 9) .…”