The electrodeionization process (EDI)with frequent polarity reversal

consisting of dilute and concentrate compartments both filled by ion-exchange resins

was developed to avert the difficult problem of deposit of metal hydroxide in treating heavy metal ions-containing solution.With feed of dilute NiSO4 solution

using operation processing: partial circulation of concentrate stream and successive switching of dilute and concentrate streams

both the high retention rate of desalination water and high concentrating ratio of concentrated product water were achieved just in a single process of EDIR.The best separation could be attained when the period of polarity reversal was 4 h.For NiSO4 solution feed containing 50 mg·L-1 Ni 2+ and pH of 3.0

the Ni 2+ concentration in exit dilute and concentrate streams could reach 1.5 mg·L-1 and 3961 mg·L-1

and the efficiency of Ni 2+ removal was 97% and the concentrating ratio 79.2

respectively

approaching theoretical value.In the experimental range

the EDIR process could be operated with good stability and without Ni (OH)2 deposit.