Mitigation of mineral scaling in membrane capacitive deionization – Understanding the role of pH changes and carbonates

• Published in: Journal of water process engineering Vol. 60; p. 105094
• Main Authors: Arulrajan, Antony Cyril, Wu, Min-Chen, Porada, Slawomir, Dykstra, Jouke E., Hou, Chia-Hung, van der Wal, Albert
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2024
• Subjects: Dissolved inorganic carbon; Ion-exchange membrane; Membrane capacitive deionization; Mineral scaling; pH changes; Ion-exchange membrane; pH changes; Membrane capacitive deionization; Dissolved inorganic carbon; Mineral scaling
• ISSN: 2214-7144; 2214-7144
• DOI: 10.1016/j.jwpe.2024.105094

Mineral scaling in water desalination is caused by the precipitation of salts, which is affected by various factors such as the presence of specific ions, solution pH, and temperature. While extensively researched in technologies like reverse osmosis (RO), understanding mineral scaling in membrane capacitive deionization (MCDI) remains limited. During MCDI operation, the pH of the effluent fluctuates, potentially triggering mineral scaling. The present study investigates how the adsorption and desorption of HCO3− ions and the distribution of dissolved inorganic carbon (DIC) species (H2CO3, HCO3−, and CO32−) drive pH changes. We examine mineral scaling formation at various water recoveries during MCDI operation using different thicknesses of the anion exchange membrane (AEM). Our findings indicate that pH changes increase with higher water recoveries and that increasing the AEM thickness provides a pathway to enhance MCDI stability, consequently lowering the need for anti-scaling agents. [Display omitted] •pH changes during tap water desalination using MCDI are due to adsorption and desorption dissolved inorganic carbon.•pH changes lead to mineral scaling, especially at higher water recovery (WR) conditions (i.e., WR > 50%).•Increasing the thickness of the anion exchange membrane (AEM) reduces mineral scaling.