Bioinspired Dual-Electric-Channel Membrane for Efficient Photothermal Evaporation and Ion-Selective Crystallization.

Abstract

Inspired by the selective salt-secretion mechanism of mangrove plants, we proposed a graphene oxide/polyamide (GO/PA) ion-selective photothermal membrane that seamlessly integrates water evaporation, ion separation, and purified salt crystallization in a single interfacial evaporation procedure. Owing to the hydrolysis of functional groups in both GO and PA layers, the intermediate region between GO and PA layers functions as a dual-electric channel (DEC), which actively drives ions toward crystallization at the membrane margin edges. Based on PA separation, DEC salt secretion, and GO photothermal evaporation, the biomimetic membrane selectively crystallized the NaCl/Na2SO4 solutions with a concentration up to 200 g/L, achieving a crystallization rate of 202.2 g m-2 h-1 and a NaCl mole fraction of 97.16%. In addition, DEC significantly alleviates salt accumulation within the membrane, prompting the evaporation rate of water up to 2.293 kg m-2 h-1 with a peak thermal efficiency of 95.53%. The GO/PA membrane also demonstrates outstanding robustness and versatility, enabling selective crystallization of a wide range of salt pairs. This pioneering concept of utilizing ion channels for selective salt crystallization and separation during solar-driven evaporation opens new avenues for advancing solar interfacial evaporation technologies, particularly in complex, high-salinity, and ionic environments.