A novel nature-assisted bipolar membrane electrodialysis strategy for hypersaline wastewater treatment: Desalination and green resource recovery pathway expansion

Bipolar membrane electrodialysis (BMED) is a promising technology for the treatment and resource recovery of hypersaline wastewater. However, using BMED alone to produce high-concentration acid and base often results in high energy consumption and challenges related to membrane stack durability. In this study, a novel BMED-coupled solar interfacial evaporation (BMED-SIE) technology is proposed. This technology first utilizes BMED to achieve desalination of hypersaline wastewater while generating low-concentration acid and base. The SIE process further concentrates these products and improves their quality under near-zero energy consumption conditions, while simultaneously recovering reclaimed water. Results show that BMED achieved a 94.6% desalination rate under a 14 V operating condition, producing acid and base at concentrations of approximately 0.93 mol/L. Under simulated sunlight at 1000 W/m², SIE achieved evaporation rates of 1.45 and 1.29 kg m^-2 h^-1 for acid and base, respectively, demonstrating the kinetic feasibility of acid/base evaporation. In a closed system, when the acid and base were concentrated to 1/3 of their original volume, their concentrations increased to 2.36 and 2.70 mol/L, corresponding to 153.8 % and 190.3 % increases over the initial values produced by BMED. The primary mechanism for concentration enhancement lies in the increased kinetic energy and escape of water molecules heated by the SIE material, while strong ionic interactions retain the acid and base ions in the bulk solution. The condensation recovery rate of evaporated water vapor was approximately 95 %, and the reclaimed water quality was adequate to meet reuse requirements. This study provides an effective solution to the limitations of BMED in producing high-concentration acid and base, and proposes a new strategy for hypersaline wastewater treatment.