A deep desalination and anti-scaling electrodeionization (EDI) process for high purity water preparation

Abstract

Electrodeionization (EDI) is a composite desalination process that combines ion exchange and electrodialysis to achieve continuous deionization. However, the current EDI technology has demanding requirements for the feed water, and fouling in the stack often exists in practical industrial applications. For the above-mentioned issue, a novel deep desalination and anti-scaling EDI stack configuration was proposed. Different from previous configuration, a cation exchange membrane was added to the right side of the reverse anode exchange membrane to form a protective chamber, in which mixed bed ion exchange resin was filled with a certain proportion, Meanwhile, the influent of concentrated stream was supplied by dilute stream. Aiming at no fouling and maximum dilute water resistivity, the effect of operating conditions on the EDI process for the preparation of high purity water were studied. All the results demonstrated that for the feed water with a hardness of 7.9 mg·L−1 (calculated as CaCO3), with the proposed EDI stack configuration and a membrane stack voltage of 8 V, a concentrated flux of 6 L/h, a dilute flux of 32 L/h, the membrane stack can run stably for 400 h without fouling, and the dilute water resistivity can reach 16.1 MΩ·cm−1, the total desalination rate was 99.8%, the hardness ion removal rate was close to 100%, the energy consumption could be maintained at <0.03 KWh·m3. These results indicate that the proposed EDI stack configuration can broaden the limits of EDI feed water conditions and it is of great practical significance to realize the industrial application of the deep desalination and anti-scaling EDI model.