Tuning membrane surface wetting behavior via dual-nanomaterial functionalization for efficient water purification

Abstract

The development of antifouling membranes is pivotal for advancing membrane technology, yet flexible control over membrane properties remains challenging. Here, we present a dual-nanomaterial functionalization strategy combing surface modified silica (M-SiO₂) nanoparticles and layered double hydroxide (M-LDH) nanosheets to synergistically regulate membrane characteristics. Systematic characterizations of the nanomaterials and five nanomaterial-functionalized membranes revealed that the dual-nanomaterial systems maintained colloidal stability (zeta potentials: ∼25–140 mV at pH ∼5–7), and the dual-nanomaterial functionalized membranes exhibited smoother surfaces (R_a as low as ∼28.9 ± 5.9 nm) compared to the pristine membrane (R_a ∼41.3 ± 9.5 nm). The hierarchical surface structure of the dual-nanomaterial functionalized membranes (Mem-S2-L1, Mem-S1-L1, Mem-S1-L2) could promote Wenzel-state contact with water, resulting in faster water contact angle decline compared to the mono-nanomaterial functionalized membranes (Mem-S1, Mem-L1), thereby demonstrating enhanced hydrophilicity. Incorporation of M-LDH conferred simultaneous hydrophilicity (water contact angle as low as ∼14.3°) and oleophobicity (diiodomethane contact angle up to ∼58.6°), and brought about higher water permeabilities (up to ∼2.7 × 10⁻⁶ m s⁻¹ kPa⁻¹, twice that of the pristine membrane) with minimal compromise on rejection capability. Ten-cycle filtration tests using practical membrane bioreactor mixed liquor demonstrated robust antifouling capability across all functionalized membranes. This work establishes a versatile platform for tailoring membrane properties through nanomaterial synergy, offering adaptable solutions for diverse water treatment applications.