A gradient wettability fiber membrane for desalination and wastewater purification by solar-driven interfacial evaporation

Solar-driven interfacial evaporation is an eco-friendly and promising method for producing fresh water. Herein, a photothermal fiber membrane with gradient wettability was fabricated using hydrophilic polyacrylonitrile and hydrophobic polystyrene by Side-by-Side electrospinning technology, which can achieve salt resistance and evaporation durability at the same time. The electrospinning fiber membrane skeleton has high porosity, facilitating water transport and steam overflow. Gradient wettability can ensure a sufficient water supply to the photothermal layer and facilitate heat-mass transport in the gradient structure, thereby improving the heat utilization ratio. The evaporation rate for water is maintained at about 1.28 kg m −2 h −1 over 10 cycles. In addition, when the prepared membrane was utilized for desalination, evaporation of acid and alkaline solutions, and wastewater treatment containing organic dyes, the condensed water collected met the drinking-water standards established by the World Health Organization. This study provides a way to design gradient wettability materials used for sustainable and efficient solar-driven interfacial evaporation.