Antifouling amidoximated polyacrylonitrile-regenerated cellulose acetate composite nanofibrous membranes for oil/water separation: Membrane fabrication, performance and fouling mechanism

Industrial production and human activities have resulted in significant oil pollution issues. The utilization of electrospinning nanofibrous membranes for the separation of oil-water mixtures and emulsions has been widely adopted. However, these membranes face challenges due to their low flux and membrane fouling. In this study, we conducted a chemical modification on a novel cross-electrospinning material, amidoximated polyacrylonitrile-regenerated cellulose acetate (AOPAN-RC), through deacetylation and ammoximation conversions. This modification led to the development of a superhydrophilic and antifouling composite membrane with excellent properties. The modified composite nanofibrous membranes exhibited remarkable hydrophilicity and strong underwater superoleophobicity, indicated by an underwater oil contact angle of 157.5° ± 1.24°, as well as a high water flux value exceeding 6000 LMH. The AOPAN-RC membranes demonstrated exceptional performance in separating highly emulsified surfactant-free and surfactant-stabilized oil-in-water emulsions, achieving separation efficiencies of over 94 ± 0.8 % and 90 ± 1.1 %, respectively. Furthermore, we discovered that higher water flux and improved emulsion separation efficiency can be achieved under low pH and ionic strength conditions with minimal addition of surfactants. Moreover, due to its superior antifouling property, the membrane enables long-term separation of high-viscosity oil-in-water emulsions and actual oily wastewater under various solution conditions. Notably, the flux of the AOPAN-RC membrane did not decrease significantly, making it significantly better than the PAN-CA and PAN-RC membranes. Additionally, the separation efficiency of the AOPAN-RC membrane also surpassed that of the other two. While the presence of surfactant-surrounded oil droplets may cause irreversible fouling over time, this innovative nanofibrous membrane exhibits great potential for practical applications in the treatment of a wider range of oil-contaminated wastewater sources.