CONTINUOUS CAPACITIVE DEIONIZATION (CDI) PROCESSES TREATING HIGH-CASO4 FEEDS FOR POTENTIAL INDUSTRIAL BRINE MANAGEMENT – IMPACTS, MECHANISMS AND MITIGATIONS

Abstract

There was a lack of understanding on the impact of the high concentrations of Ca2+ and SO42- in the industrial brines to the CDI processes. This thesis evaluated the high-CaSO4 impact to the CDI processes, investigated the relevant mechanisms and demonstrated effective mitigation methods using different operational strategies and cell architectures. Significant removal decline caused by co-ion expulsion and divalent counter-ion accumulation was observed though formation of the gypsum scaling was minimized with shorted adsorption/desorption time. A new cell architecture called MMCDI was fabricated with the incorporation of the monovalent ion exchange membranes. The new MMCDI significantly mitigated the removal decline due to the rejection of the divalent ions, and improved the energy efficiency of treating high-CaSO4 feeds. The new MMCDI could be promising for future management of the industrial brines with further optimization and field tests.