Production of high purity water using membrane-free electrodeionization with improved resin layer structure

Low‐voltage and ion‐free‐reverse‐migration electrically regenerated mixed‐bed ion exchange for MEG desalination

“…When the current density was 150 A/m 2 , the voltage required was 70 V in ERMI and 420 V in MFEDI. 28 This is because the area of the electrodes increased and the distance between the electrodes decreased in ERMI, as shown in Figure 4. Therefore, the long-term problem in MFEDI that excessive voltage may damage the resins does not need to be considered in ERMI.…”

“…Unlike MFEDI, this resin bed did not need to be pressed by a spring. 28 The process was operated in a batch mode including a desalination stage and a regeneration stage. In the desalination stage, the simulated rich MEG liquid passed the resin bed downward with a flow velocity of 1.8 m/h until the effluent conductivity reached 997 μS/cm (95% of the influent conductivity).…”

“…The original electrical regeneration equipment has complex structure. 22 In recent years, Chen's group [23][24][25][26][27][28][29][30] has proposed a process with a simple structure named as membrane-free electrodeionization (MFEDI). Compared with the traditional ion exchange column, only a pair of circular electrodes installed at the upper and lower ends of the resin bed was added in the MFEDI ion exchange column.…”

“…Second, the voltage required in regeneration process is high. A total of 210 ml of resins were regenerated at a voltage of 444 V, 28 and 350 ml of resins were regenerated at a voltage of 812 V. 25 Because the volume of resin in industrial production is much larger than the experimental value, the voltage required may be higher in application. Excessively high voltage may damage the resin structure 32 ; therefore the high voltage required of MFEDI limits its application and promotion.…”

“…Su and Hu have proposed two processes to prevent the ion backward migration, but the structures of the resin bed become more complex. 25,28 And in their process, the direction of water flow is still parallel to the direction of the electric field. Therefore, the ion backward migration cannot be eliminated in principle.…”