Continuous solar-driven saturated brine separation using sawtooth photothermal fabrics with asymmetrical wetting property

Eco-friendly solar-driven water evaporation is emerging as a promising strategy for saline wastewater separation. However, due to the severe decline in evaporation performance caused by salt fouling, complete separation of water and solute for saturated brine from industrial sectors calls for alternative efficient strategies. Here, the present study proposes a sawtooth photothermal fabric with asymmetrical wetting properties for high-efficiency and continuous solar-driven saturated brine separation. The proposed sawtooth photothermal fabric comprises a hydrophobic upper layer and a hydrophilic lower layer, which together enable efficient salt rejection and continuous water transport. In addition, the sawtooth structure of the photothermal fabric creates a dual escape path for the vapor to travel from the absorber to the environment, which improves the evaporation rate and provides appropriate conditions for salt collection. The experimental results revealed that the sawtooth photothermal fabric with asymmetrical wetting properties achieved an evaporation rate of 1.43 kg m–2 h−1 for 25 wt% brine under 1 sun illumination and recovery of a considerable amount of salt. Notably, in the outdoor experiment, the evaporation rate achieved using the fabric did not decline throughout the eight days of continuous solar-driven saturated brine separation. The present study has therefore provided a simple and economical method for the treatment of high-concentration waste brine with considerable salt recovery.