Preparation of superhydrophilic/underwater superoleophobic PA56/BNNS-OH composite nanofiber membranes and their efficient separation of oil-in-water emulsions

With the development of industrialization, the discharge of oily wastewater has been increasing significantly. In this study, a novel bio-based oil–water separation membrane was developed using bio-based Polyamide 56 (PA56) as the matrix material, which was modified by incorporating hydroxylated boron nitride nanosheets (BNNS-OH) through a blending approach. The PA56/BNNS-OH composite nanofiber membrane was fabricated via electrospinning. The impact of adding BNNS-OH on the morphological structure, selective permeability, and oil–water separation performance of the composite nanofiber membrane was explored. The results showed that, the introduction of BNNS-OH increased the surface roughness of the nanofiber membrane, forming a micro-nano nodular structure. This not only significantly enhanced the membrane’s hydrophilicity but also endowed it with outstanding underwater superoleophobicity. The M−3 membrane, prepared with 5 wt% BNNS-OH relative to PA56 content, exhibited superhydrophilic/underwater superoleophobic properties. It demonstrated efficient separation performance for various types of surfactant-stabilized emulsions (SSEs), with a separation efficiency of 99.84% for n-hexane-based SSE, approaching complete separation. Moreover, the membrane exhibited excellent cycling and thermal stability, chemical resistance, and self-cleaning properties under complex conditions. This study provides new insights and methods for developing novel bio-based and environmentally friendly oil–water separation membranes, which hold significant potential for application in oily wastewater treatment.