Dual strengthening strategy to fabricate structurally enhanced cellulose nanofiber composite membranes for stabilized emulsion separation.

Cellulose nanofibers (CNFs) have attracted widespread attention for their capability of producing biodegradable, environmentally safe separation membranes for sustainable water pollution treatment. However, the low mechanical strength and poor corrosion resistance prevent CNF membranes from providing long-lasting wetting stability and separation stability, resulting in poor oil/water emulsion separation efficiency. Herein, a dual structural enhancement strategy of calcium ion (Ca²⁺)-crosslinking and phytate modification was innovatively presented to fabricate CNF composite membranes with long-lasting wetting stability and mechanical stability for stabilized emulsion separation. Introducing Ca²⁺ into the fiber crosslinking system provides additional crosslinking paths to facilitate interfacial regulation while structurally strengthening of CNF composite membranes by calcium phytate formed in the phytate modification. Benefiting from this enhancement strategy, the obtained membrane exhibited excellent mechanical strength and stability, with low-stress losses when soaked in different solutions or solvents. Meanwhile, the membrane demonstrated outstanding water-wetting behavior and wetting selectivity of super-hydrophilicity and underwater superoleophobicity with an underwater oil contact angle of 152.83°, allowing for efficient separation of oil-in-water emulsions. The experimental results demonstrated that the membrane can successfully separate two representative oil/water mixtures, including surfactant-free oil-in-water emulsions (SFEs) and surfactant-stabilized oil-in-water emulsions (SSEs), displaying higher separation efficiency (99.2%) and separation fluxes (over 1000 L·m⁻²·h⁻¹) for SSEs. Additionally, the membrane exhibited positive stability and recycling performance, which possesses an excellent potential for the effective and continuous separation of water-in-oil emulsions. Based on the interfacial design and structural modulation, this study offers an efficient path for developing CNF-based membranes with reinforced structures. [ABSTRACT FROM AUTHOR]