A freestanding dual-cross-linked membrane with robust anti-crude oil-fouling performance for highly efficient crude oil-in-water emulsion separation

Hydrogel membranes generally possess weak mechanical properties , and the membrane surface is susceptible to abrasion, which results in the loss of superwetting properties and oil/water separation ability. Therefore, we prepared a flexible freestanding membrane using a dual-cross-linking approach. A mixed solution of sodium alginate (SA) and polyvinyl alcohol (PVA) was covalently and ionically cross-linked with borax and calcium chloride (CaCl 2 ) to form a hydrogel, and sodium carbonate (Na 2 CO 3 ) solution was then added to synthesize calcium carbonate (CaCO 3 ) in situ. The combination of covalent and ionic cross-linking improves the tensile strength . The prepared SA/PVA/borax/CaCO 3 (SPBC) membrane maintained excellent superwetting properties and oil/water separation ability, even after abrasion. The SPBC membranes have broad application prospects in the oily wastewater purification owing to their numerous advantages, such as cost effectiveness, high separation efficiency, and improved mechanical strength .