Ampholytic Chitosan/Alginate Composite Nanofibrous Membranes with Super Anti-Crude Oil-Fouling Behavior and Multifunctional Oil/Water Separation Properties

Owning to its highly viscous and adhesive properties, viscous crude oil tends to easily adhere onto separation materials, resulting in serious fouling. Herein, we report an ampholytic nanofibrous membrane composed of a pair of oppositely charged biopolymers—positive chitosan (CS) and negative sodium alginate (ALG). CS and ALG were homogeneously complexed with each other to form a well-defined, interconnected, and entangled nanofibrous structure in a cosolvent of the LiOH/KOH/urea aqueous system after sequential treatment with chemical and physical cross-linking reactions. Benefitting from the coexistence of cationic and anionic groups on the surfaces of the CS/ALG composite nanofibers, the resulting CS/ALG composite nanofibrous membrane (CAM) has a strong hydrate layer to repel various oils including viscous crude oil. Moreover, The CAM could retain its wettability in harsh environments (e.g., acid, alkali, and salt). Furthermore, it could effectively separate the most troublesome crude oil-in-water emulsions with a superior separation efficiency (99%) and behaved well in terms of reusability. Meanwhile, CAM could realize multifunctional water treatment, where water-soluble dyes and heavy metal ions could be effectively wiped off by CAM from oily wastewater. The superiorities in low-cost, biodegradability, antioil fouling performance, oil/water separation properties, as well as multifunctional water treatment endow CAM with great potential in dealing with practical oily wastewater treatment.