Cellulose-based underwater superoleophobic coatings with robust anti-viscous oil-fouling property for complex oily wastewater remediation.

Underwater superoleophobic coatings, known for their anti-oil-fouling properties, have garnered significant interest in the context of oily wastewater remediation. However, these coatings encounter challenges in preventing viscous oil contamination and structural damage, and easily become ineffective when treating crude oil/water pollutants. Additionally, the non-renewable and non-biodegradable components pose a huge risk to environmental safety and sustainable development. Herein, a cellulose-based coating that combines robust underwater superoleophobicity with anti-viscous oil-fouling characteristic is designed via the extraction of micro/nanoscale heteromorphic cellulose crystals (EHCC) and subsequent crosslinking with carboxymethyl chitosan (CCS). Leveraging the hierarchical micro/nanostructures constructed by EHCC and intensified hydration capability facilitated by multiple hydrogen bonding interactions, the EHCC-CCS coating demonstrates excellent superhydrophilicity/underwater superoleophobicity and ultralow-viscous oil-adhesion property. Moreover, the EHCC-CCS coating exhibits robust chemical resistance and mechanical tolerance. Importantly, it adapts effectively to various flat and porous substrates, offering outstanding anti-oil-fouling and self-cleaning performances. Notably, the EHCC-CCS-coated textile is applied in separating immiscible oil/water mixtures with varying oil viscosities, and the EHCC-CCS-coated PVDF membrane achieves to purify surfactant-stabilized crude oil/water emulsion. The findings provide a straightforward and cost-effective approach for large-scale production of fully biobased coatings with durable underwater superoleophobicity and excellent anti-viscous oil-fouling capability for complex oily wastewater remediation.