Synergistic approach for carbon dioxide capture and reject brine treatment: Integrating selective electrodialysis and bipolar membrane electrodialysis

Reject brine and carbon dioxide are pollutants commonly released by industries. These pollutants often contain different types of ions, including monovalent and multivalent ions. Multivalent ions like calcium, magnesium, and sulfate can cause problems by fouling membranes and equipment. Therefore, it is important to separate these ions from the reject brine. In the context of the circular economy, it is crucial to both capture carbon dioxide and manage reject brine at the same time. To facilitate carbon dioxide capture and effective reject brine management, we propose an integrated approach that combines membrane-based technologies: selective electrodialysis (SED) and bipolar membrane electrodialysis (BMED). This integration aims to optimize the process for valorization, generating value-added products such as hydrochloric acid, carbonate/bicarbonate salts, irrigation standard water (suitable for plants that can survive in harsh conditions), and brine (sodium chloride purity of 93%). SED and BMED were separately optimized, and the effects of various factors on their performance were investigated. Several factors were considered to assess the energy consumption and separation efficiency of SED. These factors included current density, flow rate (diluate/concentrate), electrolyte flow rate, number of cell pairs, and membrane type. The energy consumption and performance of BMED were investigated by considering factors such as current density, cell pairs, and carbon dioxide flow rate. The results indicated that divalent cations, such as calcium and magnesium, are more readily rejected during selective electrodialysis than divalent anions, such as sulfate. Under optimum conditions, an average carbon dioxide capture efficiency of 51% was achieved through BMED.