Construction of magnetic and photothermal wood membrane with asymmetric wettabilities and wind drift resistance for solar-driven seawater desalination and purification

Abstract

To generate clean freshwater controllably and efficiently, Fe3O4/CNT nanomaterials and hydrophobic PVDF were introduced to delignified wood with man-made-cutting structure (D-Wood) in simple brushing method for constructing the magnetic and photothermal wood evaporator with asymmetric wettabilities and wind drift resistance. Such method could endow wood with various shapes design, outstanding magnetically sensitivity, remarkable photothermal conversion efficiency (129.08 %), high evaporation rate (1.92 kg·m−2·h−1), good dye degradability (97.23 %), and excellent wind resistance (6.6 m/s). The superhydrophilic and underwater superoleophobic bottom of Fe3O4/CNT/PVDF@D-Wood evaporator accelerated the bulk seawater transport during its evaporation procedure, but prevented the oil pollutants blocking the microchannels of evaporator during the long periods of flotation at sea. Meantime, its hydrophobic top could effectively reduce the downward diffusion of heat, and improve the salt tolerance. After 10 cycles of acid-base, ultrasound treatments and evaporating experiments, Fe3O4/CNT/PVDF@D-Wood evaporator still exhibited excellent evaporation rate and conversion efficiency, displaying remarkable repeatability and long-term durability. In weak magnetic field (3 V), its furthest response displacement and time were 5 cm and 41 s, respectively. After prolonged evaporation procedure, the magnetic responsivity of Fe3O4/CNT/PVDF@D-Wood evaporator could be in almost constant level, which offers a promising biomass product for seawater desalination and polluted-water purification.