Thermal stability of bipolar membrane electrodialysis infrastructure: quantitative analysis of heat generation differences between single- and multi-stage processes for complicated industrial wastewater treatment

This study investigates the thermal stability and energy efficiency of a three-cell bipolar membrane electrodialysis (BMED) system for treating triethylammonium phosphate spent absorbing liquor, a complicated organic saline wastewater from petrochemical industries. By integrating experimental analysis with Multisim 14.0 circuit simulations, we quantitatively evaluated heat generation patterns in both main and leakage circuits under single-stage (50 mA cm −2 ) and two-stage (50 → 30 mA cm −2 ) operational modes. Results revealed that leakage currents through slots and ducts, though accounting for only 0.15 % of total system current, induced localized Joule heating up to 101.24 mW in narrow slots due to poor heat dissipation. In contrast, the main circuit's rapid solution flow and large contact area enabled efficient heat transfer to external storage tanks, preventing bulk stack overheating. Two-stage BMED significantly suppressed thermal accumulation, reducing peak heating power in acid/base compartments by 33.9–36.2 % and feed compartments by 63.9 % compared to single-stage operation. The segmented current strategy also lowered leakage circuit heat generation by 46.6 %, mitigating risks of membrane degradation and spacer deformation. Furthermore, the study identified that the weak ionization of triethylamine in base compartments exacerbated resistance polarization, while phosphoric acid's high conductivity minimized thermal effects in acid compartments. These findings highlight the critical role of phased current regulation and leakage circuit optimization in scaling BMED for industrial wastewater treatment. Proposed strategies, including spacer geometry redesign and thin compartment fabrication, provide actionable pathways to enhance thermal management and energy efficiency, bridging the gap between laboratory-scale innovations and industrial implementation.