Amphoteric blend ion exchange resin with medium-strength alkalinity for high-purity water production in membrane-free electrodeionization

Abstract

In our previous works, membrane-free electrodeionization (MFEDI), an original deionization technique to produce high-purity water, was invented. However, traditional ion exchange resins, the heart of MFEDI, cannot simultaneously achieve effective adsorption, easy electrical regeneration, and good conductivity. Previously, an amphoteric resin, quaternary ammonium- sulfonic acid resin (QA-SAR), that behaved as medium-strength acid resin, was proposed and applied to produce high-purity water with regeneration performance superior to that of traditional resins. Although the regeneration performance of QA-SAR was better than that of traditional resins, the ion-exchange capacity and conductivity were poor, which further resulted in poor effluent and high regeneration voltage. In view of this, a novel amphoteric resin containing more anionic groups than cationic groups and behaving as medium-strength basic resin, sulfonic acid-quaternary ammonium resin (SA-QAR), was proposed herein. It exhibited better regeneration performance and purification performance than traditional resins and QA-SAR. Under the same conditions, the effluent quality of the MFEDI system filled with SA-QAR remained stable and lower than 0.1 μS/cm, with energy consumption of approximately 0.32 kWh/m3 water, whereas the effluent quality of the system filled with 550A and the system filled with QA-SAR deteriorated quickly, with energy consumption of approximately 0.36 and 0.43 kWh/m3 water, respectively.