Electrodialysis reversal desalination: optimal voltage application rate, linear velocity, and mean ion residence time for maximal ion removal rate

Abstract

Optimal voltage application rate, linear velocity, and mean ion residence time (MIRTd) in dilute stream were searched for electrodialysis reversal desalination by using two different feed waters containing TDS 3330 and 7190 mg/L NaCl. Two sets of literature data were used in the analyses. First, the relation among demineralization degree, voltage application rate, and MIRTd were derived from theory. Then, the findings were analyzed from the first set of literature data and validated with the second set of data. The analyses show that the maximal demineralization degree does not appear at the highest voltage application alone and that demineralization degree increases with the increasing voltage application rate to a certain critical value only. The maximal demineralization degree occurs at the combination of lower voltage application and longer MIRTd or vice versa. Data show the maximal demineralization degree does not always present the maximal ion removal rate per effective area of cell pairs per power. Therefore, both the maximal demineralization degree and maximal ion removal rate per effective area of cell pair per power were used to gauge optimal voltage application, linear velocity, and MIRTd. Optimal voltage application, linear velocity, and MIRTd were found to be 45–70 V, 15.1–12.3 cm/s, and 2.3–2.7 min for feed water 3330–7190 mg/L NaCl in Aquamite I membrane stack with Mark I spacer in 135 different operational conditions.