Electrospun cellulose nanofibers membranes with photothermal/pH-induced switchable wettability for oil-water separation and elimination of bacteria

Abstract

Considering the substantial annual global discharge of oily wastewater, there exists a crucial requirement to develop smart membranes that possess environmentally sustainable attributes, tunable wettability, and potent antibacterial properties, enabling efficient and controlled separation of oil/water mixtures. Here, a photothermal/pH-responsive electrospun cellulose nanofibers (ECF-P-Fe₃O₄-N) membrane endowed with wettability modulation and bacterial elimination capabilities was successfully prepared. The advancement in the fabrication method stemmed from the ingenious integration of three key strategies: the interpenetrating network formation between cellulose and the thermosensitive polymer, the co-precipitation embedding of photothermal medium (Fe₃O₄ NPs), and the chemical grafting of aminosilane. The resultant ECF-P-Fe₃O₄-N membrane exhibited fast and reversible wettability transitions between high hydrophilicity (under acid or high-temperature stimulation) and hydrophobicity (under alkali or low-temperature stimulation), achieving on-demand separation of diverse immiscible oil-water mixtures and surfactant-stabilized emulsions. The maximum separation flux for oil-water emulsions attained a value of 225.6 L m⁻² h⁻¹, accompanied by a separation efficiency surpassing 98.53 %. It also possessed strong elimination of bacteria, satisfying for the long-lasting contact usage. This work holds significant implications in designing smart membranes for remotely controlling the oil-water separation.