Superhydrophilic Sandwich Structure Aerogel Membrane for Emulsion Separation and Heavy Metal Ion Removal

Water pollution has been increasingly becoming a serious environmental and health challenge in recent years. This is compounded by the often coexisting oil pollution and heavy metal pollution. It is of great practical significance to develop materials that can simultaneously deal with these two kinds of water pollution problems. In this study, a simple and green approach is proposed for preparing matrix-free citric acid modified alginate-based aerogel membrane by simple sol spraying, chemical cross-linking, and freeze-drying methods. The aerogel membrane with dense upper and lower surfaces and a loose interlayer possesses the properties of superhydrophilicity and underwater superoleophobic and strong antiadhesion performances, and it can realize the separation of highly viscous miscible oil–water emulsions with a separation efficiency of over 99.5%, even in corrosive and high-salt environments. The membrane has shown strong stability during 3000 min of uninterrupted cross-flow filtration of emulsion, which reflects the good long-term separation performance of the membrane. The prepared membrane can also be used for the removal of various heavy metal ions from water under gravity, with a removal efficiency >99% and an adsorption capacity of about 240 mg/g for Pb2+. The modified membrane which features low cost, a simple and green preparation process, excellent oil–water separation, and heavy metal removal capabilities possesses great application potential in the treatment of polluted water.