Work

Lab-scale experiments with a monovalent ion selective membrane capacitive deionization for nitrate removal

Year: 2025

Type: article

Abstract: Groundwater with high nitrate concentrations requires treatment before potable use. Conventional treatment methods such as nanofiltration and reverse osmosis can be used for desalination of most solutes. In contrast, a monovalent selective membrane capacitive deionization (mMCDI) can be used for selective nitrate removal. We use a nanofiltration membrane and anion exchange membranes with an additional neutral layer (AEM-Neutral) or a polyamide layer (AEM-PA) for selective nitrate removal with mMCDI by using a solution of mixed monovalent and polyvalent ions. Monovalent ion selectivity in short-term experiments is up to 17.3 with a nanofiltration membrane, up to 1.7 for AEM-Neutral and up to 5.2 for AEM-PA, whereby the specific energy consumption and water recovery depends on cell structure, applied electric voltage, flow rate and desorption time. Selective nitrate removal with AEM-PA or AEM-Neutral at 0.8 V demonstrated a specific energy consumption of 2 Wh g −1 removed nitrate, lower than pressure-driven membrane processes. • NF membranes are very selective towards nitrate but show a low removal efficiency. • Coated AEMs show a selectivity towards nitrate with a high removal efficiency. • mMCDI can be an alternative for NF/RO for nitrate removal in groundwater. • A low voltage and a high flow increase the monovalent ion selectivity in mMCDI.

Source: Water Resources and Industry

DOI: 10.1016/j.wri.2025.100288