Durable, cost-effective and superhydrophilic chitosan-alginate hydrogel-coated mesh for efficient oil/water separation

•The double-cross-linked chitosan-alginate hydrogel coating was fabricated on Cu mesh.•The hydrogel coating showed outstanding underwater superoleophobicity.•The hydrogel-coated mesh could achieve oil/water separation with high efficiency.•The mesh exhibited excellent stability and durability in hypersaline environments. Hydrogels with low-adhesive superoleophobicity are ideal candidates for modifying filtration substrates to achieve efficient and antifouling oil/water separation. However, there are still some unfavorable factors hindering their practical application, including expensive raw materials, complex fabrication process, poor stability and durability. In this work, a durable, cost-effective and superhydrophilic chitosan-alginate (CS-ALG) hydrogel coated mesh was developed by a facile, two-step dip-coating method for efficient oil/water separation in hypersaline environments. By integrating polysaccharide-based superhydrophobic surfaces and the hierarchical micro-/nanostructures, the as-fabricated CS-ALG hydrogel coated mesh exhibits excellent underwater superoleophobicity and anti-oil-fouling performance. Benefiting from that, the mesh could separate various oil/water mixtures with high separation efficiency (> 99%). It is worth mentioning that the double-cross-linked CS-ALG hydrogel based on sequential electrostatic interaction and ionic cross-linking shows excellent durability in hypersaline environments. All these attractive advantages make the hydrogel-coated mesh a promising candidate for oily wastewater treatment and oil spill cleanup.