Enhanced boron removal without pre-pH adjustment via redox-mediated electrodialysis assisted by ion-exchange resins

Abstract

Boron presents challenges in desalination owing to its small size and lack of charge. While various methods, such as reverse osmosis, capacitive deionization, and electrodeionization, have been utilized to control boron, they often suffer from high levels of energy consumption and complex processes requiring pH adjustment to generate the charged form of boron. Herein, we introduce a novel approach, i.e., redox-mediated electrodialysis (redox-ED) assisted by ion-exchange resins, aimed at energy-efficient boron control without requiring pH adjustment. Our system displays a remarkable boron removal efficiency of 99% with a low energy consumption of 0.009 kWh/g (0.09 kWh/m3). These results are likely due to the dissociation of water on the surface of the ion-exchange resins, which led to a local pH gradient and reduced systemic resistance through additional ion flux. Furthermore, via techno-economic analysis, the total cost of the redox-ED for boron removal revealed a 50% reduction with the scale-up strategy of electrode stacking, compared to those of traditional EDI systems. Overall, this study demonstrates the new potential of a sustainable boron removal technology without pH adjustment through the redox-ED system assisted by ion-exchange resins, providing an attractive option applicable to the boron removal industry.