Interface modification of membrane substrates: Mitigating microbial interfacial adhesion and augmenting adsorptive...

Seawater is endowed with vast reserves of high-value trace metals (gold, lithium, uranium) for resource recovery. However, their extremely low concentrations entail extensive, long-duration seawater processing in membrane-based systems, leading to pronounced microbial fouling and a substantial deterioration in adsorption efficiency. Given that practical membrane modules possess a multi-component architecture, this study mitigated microbial fouling via indigo modification of membrane supporting substrates, while maintaining the structural and functional integrity of the adsorptive membrane. This approach avoids the impairment of adsorption sites and porous structures induced by direct antimicrobial modification of the membrane. Column breakthrough experiments were employed to assess the fouling characteristics and severity of membrane modules in terms of macroscopic retention and structural evolution. Before modification, the membrane module exhibited interception rates of 79.8% and 77.3% for single strains and in-situ marine microbial communities (multiple strains), respectively, which were reduced to 45.6% and 57.1% after modification. Analysis using the dual-kinetic-site attachment-detachment model demonstrated that indigo-modified substrates reduced Langmuirian attachment and ripening, while the functional complementarity within microbial communities mitigated these effects. Metagenomic analysis confirmed that the modification selectively suppressed the attachment of microorganisms with strong adhesion and biofilm-forming ability. In a 28-day adsorption validation in real seawater, the modification increased the uranium adsorption capacity from 1.05 to 2.38 mg/g, effectively attenuating the performance decline induced by microbial contamination. The spatially decoupled integration of substrate anti-adhesion and membrane adsorption offers a new paradigm for membrane module design and optimization, extending its application potential in marine uranium recovery.