Superwetting PVA/cellulose aerogel with asymmetric structure for oil/water separation and solar-driven seawater desalination

Extracting clean water from oily wastewater and seawater is one of the effective strategies to alleviate the freshwater crisis. However, achieving both high separation efficiency and excellent salt resistance remain challenges for materials. Herein, a novel methyltrichlorosilane-modified polyvinyl alcohol/cellulose aerogel (MPCA) was prepared by freeze drying, chemical cross-linking, and chemical vapor deposition (CVD) methods. The superwetting MPCA presented an asymmetric structure, in which the small dense pores at the top surface facilitated the efficient separation of water-in-oil (W/O) emulsions and the large pores on the bottom surface were beneficial for brine exchange. The as-prepared superwetting aerogel was suitable for the separation of various W/O emulsions with excellent separation flux (631.9-2368.7 L·m-2·h-1) and outstanding separation efficiency (99.5%). In addition, MPCA achieved a high evaporation efficiency of 1.39 kg·m-2·h-1 and a satisfactory energy conversion efficiency of 89.7%. Moreover, the unique asymmetric structure endowed the evaporator excellent salt resistance and could self-dissolve the accumulated salt in 20 minutes. The as-prepared MPCA could achieve efficient W/O emulsion separation as well as produce freshwater in seawater, providing a new strategy for oily waste seawater purification. The discharge of oily wastewater not only damages the ecosystem but also threatens human health. Superwetting separation materials can efficiently treat various oily wastewaters, but they cannot remove water-soluble pollutants in the water. A novel superwetting Janus cellulose/PVA aerogel (MPCA) was prepared, with dense pores on the top surface to facilitate the separation of water-in-oil emulsion, and large honeycomb pores on the bottom to facilitate the continuous supply of water and ion exchange. The as-prepared MPCA could not only efficiently separate water-in-oil emulsions, but also produce clean water under light irradiation, providing a new strategy for alleviating the freshwater crisis.