Electrospinning Machine | CoFe-LDH “Armour” modified nanofiber membrane with multiple synergistic effects for wastewater purification

Petroleum industry wastewater and organic dyes and other pollutants pose a serious threat to the water environment and human health, receiving increasing widespread attention. To achieve stable loading of catalysts on nanofiber membranes, it is usually necessary to introduce polydopamine or plant polyphenols on the surface of the polymer-based nanofiber substrate to provide catalytic sites and enhance interfacial bonding strength. However, in practical applications, the physicochemical stability of these modification layers has limitations. Therefore, screening active materials with both stability and universality as anchor sites for catalyst growth is crucial. Cellulose nanofibers (CNF), with their excellent hydrophilicity, structural stability, and abundant surface functional groups, can achieve tight integration with the fiber substrate and firmly fix the catalyst.

Recently, Associate Professor Atian Xie of Anhui University of Science and Technology & Professor Jianming Pan of Jiangsu University published the latest research results "CoFe-LDH 'Armour' modified nanofiber membrane with multiple synergistic effects for wastewater purification" in the journal "Chemical Engineering Journal". This work prepared polyacrylonitrile (PAN)/cellulose nanofiber (CNF)@cobalt-iron layered double hydroxide (CoFe-LDH) nanofiber membrane (PCLNFM) through electrospinning and in-situ growth methods. PCLNFM can effectively separate various surfactant-stabilized oil-water emulsions, achieving a separation flux of up to 260.7 L m⁻² h⁻¹ and 99.7% separation efficiency even in acidic, alkaline, and salt environments. Furthermore, PCLNFM can treat emulsion/methylene blue (MB) mixed wastewater. Moreover, PCLNFM exhibits excellent self-cleaning capability, with a flux recovery rate of up to 99.3% after simple PMS catalytic self-cleaning.

Figure 1: Morphology of PCLNFM

SEM observation shows that PCLNFM has a good three-dimensional porous structure, and the layered double hydroxide has good overall dispersion in PCLNFM. The protrusions formed on the fiber surface help improve the wettability of the composite membrane, enhancing the separation and catalytic performance of the membrane.

Figure 2: Mechanical properties of PCLNFM

PCLNFM-9 has good mechanical properties, and its tensile strength is about 7.6 times that of the original membrane. This is because the synergistic effect of CNF and LDH significantly enhances the mechanical stability of the nanofiber membrane.

Figure 3: Surface wettability of PCLNFM

Water contact angle (WCA) and underwater oil contact angle (UOCA) tests show that the optimized PCLNFM-9 has a WCA of 0° and a UOCA of 161.9°, proving that PCLNFM-9 has superhydrophilicity/underwater superoleophobicity, giving it good application potential in oil-water separation.

Figure 4: Oil-water separation and oil-water-dye separation performance of PCLNFM-9

Research shows that PCLNFM can achieve effective separation of various tested emulsions (>99%), with separation fluxes all above 260 L m⁻² h⁻¹. Optical micrographs and particle size distribution of the emulsion and filtrate indicate that the nanofiber membrane successfully traps oil droplets in water and can also effectively separate oil-dye mixed emulsions.

Figure 5: Oil-water emulsion separation performance of PCLNFM-9 under different conditions.

PCLNFM-9 can still maintain high flux (>250 L m⁻² h⁻¹) and separation efficiency (>99%) in acid, alkali, and salt solutions. The results show that PCLNFM-9 can still separate oil-water emulsions under acid, alkali, and salt solution conditions.

Figure 6: Performance of PCLNFM-9 catalytic activation of PMS to degrade methylene blue.

PCLNFM-9-PMS system achieved a 98% degradation rate of methylene blue within 40 minutes, indicating that PCLNFM-9 has good catalytic performance. In summary, this nanofiber membrane with good mechanical stability, combined with superhydrophilicity and catalytic self-cleaning function, shows significant application potential in the field of oil-water emulsion separation and dye wastewater treatment.

Paper link: https://doi.org/10.1016/j.cej.2025.167572