Utilization of Bipolar Membrane Electrodialysis for Salt Water Treatment

Abstract

Bipolar ion-exchange membranes, using polystyrene ethylene utylenes polystyrene (PSEBS) with polyvinyl alcohol as the intermediate, were fabricated and evaluated for their potential to remove secondary salts from lab-prepared salt solutions. Experiments were carried out in batch re-circulation mode. The mechanical properties and microscopic images of the membranes were analyzed before, during, and after the electrodialysis process. The performance of the membranes in the stack was evaluated in terms of energy consumption and current efficiency, and found to be 1.07 Wh/mol and 0.67, respectively. Commercially-produced membranes were used as a comparison to the PSEBS-based membranes. In the case of the commercial membrane, polystyrene divinylbenzene, the values for the above parameters were observed to be 2.59 Wh/mol and 0.63, respectively. In addition, other parameters, such as transport number of ions and acid - alkali production, were evaluated for both PSEBS-based and commercially-produced membranes. Results indicated that PSEBS-based membranes exhibited better performance than the commercial membranes.

Recent Advances in Bipolar Membrane Design and Applications

“…A typical desalination BPMED design is shown in Figure . A salt solution is passed between a CEM and an AEM, where under operation the Na ions and Cl ions electrodiffuse into separate compartments to combine with the hydroxide ions or protons generated by the BPMs, with water-splitting reactions occurring at the electrodes to complete the system.…”

“…(a) Schematic representation of a BPMED used for desalination processes. Reprinted with permission from ref . Copyright 2013 Water Environment Federation.…”

“…A typical desalination BPMED design is shown in Figure 9. 184 A salt solution is passed between a CEM and an AEM, where under operation the Na ions and Cl ions electrodiffuse into separate compartments to combine with the hydroxide ions or protons generated by the BPMs, with water-splitting reactions occurring at the electrodes to complete the system. Dilute NaOH and HCl solutions are initially introduced into the product streams to reduce the cell resistance, with the NaOH and HCl concentration increasing during BPMED, Figure 9.…”

Bipolar Membrane Electrodialysis for Binary Salt Water Treatment: Valorization of Type and Concentration of Electrolytes

“…3,7,9−15 This ability allows faster generation of proton and hydroxyl ions than aqueous solutions for the production of acid and base. 9,11,14,15 Compared to electrodialysis-based membrane processes, energy consumption and unit cost in BMED are lower. However, the operational cost of the BMED system is higher than the others due to the periodic changing requirement of the highcost bipolar membrane (BPM).…”

“…In addition to desalination, the BMED process results in the production of acids and bases from the related salts without any chemical addition. Water dissociation in BMED interfaces under an electrical field is the most important ability of BMED. ,,− This ability allows faster generation of proton and hydroxyl ions than aqueous solutions for the production of acid and base. ,,, Compared to electrodialysis-based membrane processes, energy consumption and unit cost in BMED are lower. However, the operational cost of the BMED system is higher than the others due to the periodic changing requirement of the high-cost bipolar membrane (BPM). ,, In a BMED system, H 2 and O 2 are not formed in the gaseous phase, while salt ions leaked through BPM can cause impurities in acid and base tanks. ,,,, Since BMED provides acid and base recovery during wastewater desalination, its application potential is continuously increasing in the chemical process industry.…”