Selective electrodialysis: a sustainable approach for fluoride removal from drinking water

The removal of fluoride ions from drinking water is critical for mitigating health risks associated with excess exposure. While conventional membrane-based water treatment technologies often suffer from high operational costs and secondary pollution, electrodialysis (ED) has emerged as a promising alternative due to its operational simplicity, scalability, and efficiency. This review critically examines the mechanisms, membrane properties, operational conditions, and long-term challenges that govern F⁻ selectivity in ED. Key findings highlight that membrane characteristics including ion-exchange capacity, water content, thickness, cross-linking, and functional chemistry, directly influence F⁻ transport, while targeted modifications can further enhance selectivity and reduce fouling. Operating parameters interact strongly: high current density coupled with increased flowrate improves F⁻/Cl⁻ separation, whereas elevated pH intensifies competition from OH⁻. Fouling presents a critical challenge to long-term selectivity, occurring through a two-stage process of early organic deposition followed by inorganic scaling; sequential acid–base cleaning has proven effective in restoring performance. Compared to alternatives, ED achieves higher water recovery with lower brine volumes, and, when coupled with solar PV, is cost-effective and well-suited for decentralized community-scale treatment. Overall, ED is positioned as a sustainable and technically robust option for fluoride mitigation, with future progress dependent on innovations in membrane design, parameter optimization, and fouling control to enable real-world deployment.