Membrane-free electrodeionization (MFEDI) has been tested successfully for high purity water production in our previous work. However, in order to prevent the constant backward migration of cationic or anionic ions, to achieve equally effective regeneration for both the cationic and anionic resins, and to get neutral concentrate, the electrodes had to be reversed during regeneration. This not only complicated the regeneration process, but also decreased the water recovery and the electrode lifetime. In this work, we improved the resin layer structure and investigated the regeneration performance of MFEDI without electrode polarity reversal . A total of 30 operational cycles were examined. Effective regeneration was achieved. The effluent conductivity was 0.055–0.060 μS/cm only; the average pH value of the concentrate was 7.2; the water recovery was 90%; and the energy consumption was 0.71 kWh/m 3 water.
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/m 3 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/m 3 water, respectively.
危险品化学品经营许可证（带存储）