Air filtration constitutes the mainstream microbial sampling approach, whereas traditional rigid filter substrates are plagued by incomplete microbial elution and low adaptability to post-sampling analytical workflows. Herein, a tannic acid (TA)-reinforced gelatin/carboxymethyl chitosan composite filter membrane (TGFM) is fabricated via ethanol-induced co-assembly followed by green unilateral surface crosslinking. The tunable TA dosage precisely optimizes surface compactness while retaining the intrinsic honeycomb porous network, endowing TGFM with full water dissolvability, balanced air permeability, and high airborne bacterial capture efficiency. Benefiting from mild polyphenol modification, TGFM exhibits outstanding bacterial biocompatibility and rapid soil biodegradability, which consistent well with green chemistry principles. Comparative bioaerosol tests demonstrate that TGFM filtration sampling consistently outperforms classic impactor and sedimentation approaches under variable contamination levels. Consistent and reliable microbial detection data can also be stably provided by TGFM during on-site sampling in the real-world cell-culture room and underground parking garages. In addition, the integration with commercial petrifilm for rapid bacterial detection establishes an accelerated analytical workflow that shortens the microbial incubation cycle while maintaining counting accuracy. This work proposes a green surface reinforcement strategy to address the inherent drawbacks of single physical assembly, offering an eco-friendly and practical capture-to-detection platform for airborne bacterial monitoring.
Complex oily wastewater typically contains both surfactant-stabilized oil droplets and dissolved organic pollutants, requiring a membrane material capable of efficient interfacial separation and catalytic pollutant removal. In this work, coal fly ash (CFA) was used as a low-cost aluminum source to construct hierarchical AlOOH@TiO2 nanoflowers. These were immobilized on a nylon substrate via a bilayer polydopamine/polyethyleneimine (PDA/PEI) structure to fabricate a sandwich-structured membrane. The lower layer PDA/PEI network strengthened AlOOH@TiO2 nanoflower adhesion to the nylon substrate, whereas the upper layer network inhibited AlOOH@TiO2 shedding. Amino groups in PDA/PEI and hydroxyl groups on AlOOH@TiO2 rendered the membrane superhydrophilic/underwater oleophobic, with an underwater oil contact angle of 161.2 ± 0.2°. The open nanoflower structure enabled a maximum membrane permeance of 5200 L m-2 h-1 bar-1. Based on hydration-layer effects, electrostatic repulsion, and steric hindrance, the membrane achieved over 99.9% separation efficiency for surfactant-stabilized oil-in-water emulsions. Additionally, the membrane remained stable after repeated filtration and after acidic, alkaline, and saline conditions. Under 365 nm UV irradiation, the membrane removed 99.1% of methylene blue within 1 h, owing to UV response of TiO2 and heterointerface-promoted photocarrier separation. This study demonstrates a sustainable strategy for converting CFA into a robust dual-functional membrane for integrated emulsion separation and photocatalytic purification.
