Environmentally friendly, cellulose-based hydrogel with underwater superoleophobicity for high flux oil/water separation under harsh environments (acidic, alkaline, and saline)

The increasing incidence of oil spills and the discharge of oily industrial wastewater necessitate efficient oil-water separation technologies, particularly in extreme environmental conditions. In this study, cellulose and polyvinyl alcohol/cellulose hydrogels were synthesized and applied as coatings on stainless steel meshes to address this challenge. The coated meshes demonstrated high separation efficiencies (>98 %) for toluene, hexane, gasoline, and olive oil in acidic, alkaline, and saline environments. Remarkable reusability was also observed, with efficiencies remaining above 97.3 % after 20 separation cycles. Moreover, a high flux of 190,728 L/m²·h was achieved, and field emission scanning electron microscopy confirmed the formation of a uniform, thin hydrogel layer. Wettability assessments revealed superhydrophilicity in air (0° contact angle) and underwater superoleophobicity (oil contact angles >153°), which are critical for effective separation. Optimization studies revealed that the optimal formulation consists of a 1:2 ratio of PVA to cellulose, 5 % glutaraldehyde, and PVA with a molecular weight of 145,000. These findings highlight the potential of polyvinyl alcohol/cellulose hydrogel-coated meshes for robust and scalable oil-water separation in harsh environments.