Membrane-free electrodeionization for high-velocity production of high-purity water

Membrane-free electrodeionization (MFEDI) has been proven effective in desalination of water similar to the effluent of one-pass reverse osmosis (RO) in our previous work. In this work, we investigated MFEDI for use as a polishing desalination process after two-pass RO. In addition to the difference in simulated feedwater, we increased the flow velocity significantly from previous 15 to 70 m/h. An appropriate resin layer structure was selected to enhance resins regeneration, especially to obstruct the backward migration of cations in resin phase. Parameters of regeneration were adjusted to be more effective and energy efficient. The system was tested for over 60 operational cycles. After such a long-term service, the effluent conductivity still maintained below 0.060 μS/cm. Water recovery rate and energy consumption of the system were around 93% and 0.14 kWh/m3 water, respectively. MFEDI was proven to be an economic and quality assured alternative for high-purity water production.