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Article

Exploration of Methods for In Situ Scale Removal During Magnesium Hydroxide Membrane Crystallization

Institute of Chemical and Environmental Engineering, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37 Bratislava, Slovakia
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Membranes 2025, 15(9), 267; https://doi.org/10.3390/membranes15090267
Submission received: 31 July 2025 / Revised: 28 August 2025 / Accepted: 1 September 2025 / Published: 3 September 2025

Abstract

In coastal countries facing a shortage of drinking water, seawater desalination is essential for the production of potable water. During desalination, a large volume of waste stream, known as brine, is generated. This stream contains high concentrations of salts, particularly those of economic importance to the European Union, such as magnesium and calcium. By further processing this stream, these materials can be recovered. One method studied for separating magnesium from wastewater is membrane crystallization (MCr). The MCr process developed in this work utilizes ion-exchange membranes that separate the model brine solution from a precipitating agent, which is a solution of sodium hydroxide. During the process, the membrane allows the transport of anions between the two solutions, enabling the reaction between OH anions and Mg2+ cations, which leads to the formation of a magnesium hydroxide precipitate. The formed precipitate can then be filtered out of the brine solution, which now has decreased salinity due to crystallization facilitated by the ion-exchange membrane. However, precipitation occurs near the membrane surface, resulting in the deposition of magnesium hydroxide onto the outer surface of the membrane. The aim of this study is to investigate methods for effectively removing magnesium hydroxide from the membrane surface, with a primary focus on maximizing the yield of magnesium hydroxide crystals in suspension. Crystal removal was induced by circulation of hydrochloric acid, followed by circulation of demineralized water through the membrane module after crystallization. In this study, a membrane module made of hollow-fiber anion-exchange membranes was employed. The production cost of these membranes is approximately 50% lower per square meter compared to flat-sheet membranes commonly used in electrodialysis, demonstrating strong potential for commercial application. More than 85% magnesium conversion was achieved during the process, yet the majority of the crystals remained attached to the membrane. Circulation of hydrochloric acid and demineralized water after the crystallization process caused detachment of the crystals into suspension, nearly doubling their yield.
Keywords: membrane crystallization; magnesium hydroxide; hollow fiber anion-exchange membrane membrane crystallization; magnesium hydroxide; hollow fiber anion-exchange membrane

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MDPI and ACS Style

Komačková, E.; Sedlák, L.; Červeňanský, I.; Markoš, J. Exploration of Methods for In Situ Scale Removal During Magnesium Hydroxide Membrane Crystallization. Membranes 2025, 15, 267. https://doi.org/10.3390/membranes15090267

AMA Style

Komačková E, Sedlák L, Červeňanský I, Markoš J. Exploration of Methods for In Situ Scale Removal During Magnesium Hydroxide Membrane Crystallization. Membranes. 2025; 15(9):267. https://doi.org/10.3390/membranes15090267

Chicago/Turabian Style

Komačková, Ester, Lukáš Sedlák, Ivan Červeňanský, and Jozef Markoš. 2025. "Exploration of Methods for In Situ Scale Removal During Magnesium Hydroxide Membrane Crystallization" Membranes 15, no. 9: 267. https://doi.org/10.3390/membranes15090267

APA Style

Komačková, E., Sedlák, L., Červeňanský, I., & Markoš, J. (2025). Exploration of Methods for In Situ Scale Removal During Magnesium Hydroxide Membrane Crystallization. Membranes, 15(9), 267. https://doi.org/10.3390/membranes15090267

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