Membrane-free electrodeionization without electrode polarity reversal for high purity water production

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/m3 water.