Polyphenolic engineering of MoS₂ ceramic membranes for oily wastewater separation

The treatment of oily wastewater is challenging due to significant membrane fouling, which results in a reduction in separation efficiency. In this work, a fouling-resistant molybdenum disulfide (MoS₂)-based ceramic membrane has been prepared through functionalized MoS₂ with polydopamine-tannic acid (PDA-TA) coating for the treatment of oil-in-water emulsion. The functionalization substantially enhanced the processability of MoS₂ nanosheets while simultaneously enhancing interfacial adhesion, surface hydrophilicity, and underwater oleophobicity, without disrupting the intrinsic MoS₂ crystal structure. Systematic loading control of MoS₂ has shown a clear correlation between structure and performance. A thin and stable separating layer was obtained at a functionalized MoS₂ loading of 10 mg, delivering a steady pure-water flux of 714 L m⁻² h⁻¹ and an oil droplet rejection above 97% at 0.5 bar. The functionalized membranes exhibited high underwater superoleophobicity (oil contact angle ∼ 150°), high antifouling capacity, and high flux recovery ratio following cyclic filtration of surfactant-stabilized oil-in-water emulsion. Performance of the separation remained steady at a wide range of operating pressures (0.5–15 bar) as well as oil concentrations (200–600 ppm). Synergistic effects of laminar MoS₂ nanochannels and hydration layers induced by PDA-TA effectively prevented oil adhesion and fouling. Overall, this work has demonstrated a robust method for fabricating high-performance MoS₂-based ceramic membranes, with strong potential for use in treating oily wastewater.