Ultrafiltration membrane based on PES/CeO₂-MoS₂ heterostructured nanocomposites for enhanced oil-in-water emulsion separation and antifouling

Low permeance and poor fouling resistance are major bottlenecks in membrane-based treatment of oily wastewater, especially in the treatment of oil-in-water emulsions. This study reports the modification of PES membranes with a cerium oxide (CeO₂)-molybdenum disulfide (MoS₂) nanocomposite, enhancing their antifouling properties against oil droplets in water. The high dispersion property of MoS₂ and the polar surface functional characteristics of CeO₂ lead to the forced surface segregation of CeO₂-MoS₂ in the PES membrane structure, enhancing both hydrophilic-oleophobic characteristics and surface smoothness. The polyethersulfone (PES)/CeO₂-MoS₂ membrane was fabricated using nonsolvent-induced phase inversion (NIPS) with different weight percentages (wt.%) of CeO₂-MoS₂. The prepared membranes were tested for their structural characteristics, hydrophilicity, surface roughness, and porosity. The best-performing PES/CeO₂-MoS₂ membrane, with a 0.5 wt% loading (M−0.5), exhibited membrane porosity, pore size, surface smoothness, contact angle, and zeta potential values of 68.5 %, 64 nm, RMS 2.7 ± 0.5 nm, ∼52°, and −27 mV at pH 7, respectively. The M−0.5 exhibited a 64 % increase in pure water flux compared to the pristine membrane. In oil-in-water emulsion filtration, the M−0.5 achieved fluxes of 333, 277, and 235 L m⁻²h⁻¹, and oil rejections of 96 %, 98 %, and 99 % for 100, 500, and 1000 ppm oil-in-water feed solutions, respectively. After three filtration cycles with oil-in-water emulsion, the M−0.5 maintained a satisfactory flux recovery ratio (FRR) of 77.6 % and a low reversible fouling rate (Rr) of 50.2 %. These results demonstrate excellent filtration performance and recyclability, highlighting the potential of the PES/CeO₂-MoS₂ membrane for oil-in-water emulsion separation applications..