Cr(VI) removal by continuous electrodeionization: Study of its basic technologies

This study investigates the capabilities of the continuous electrodeionization process (CEDI) and its fundamental technologies, including electrodialysis (ED) and ion exchange (IX), for the removal of hexavalent chromium from synthetic solutions at pH 5. A specially designed cell featuring two chambers, one for dilute and the other for concentrate solutions, was utilized. The research employed two cation exchange membranes and one anion exchange membrane, with an effective area of 40 cm². The performance of IX was assessed independently using an IRA-67 anionic resin to establish its effectiveness away from the other technologies. The ED process involved the use of I vs. U plots, applying factors of 0.7Ilim and 0.85 Ilim. The EDI process was also analyzed under conditions identical to the ED to evaluate the role of the resin bed. The removal efficiency observed was 50% for IX, 98% for ED after 6.25 hours with an energy consumption of 1.21 kWh/m³, while EDI with the anionic bed achieved 97.55% removal at 0.91 kWh/m³. Notably, the EDI system with mixed bed removed 99.8% of chromium in 1.3 hours at a lower energy consumption of 0.167 kWh/m³.