Quorum sensing-driven biofilm cathode of Shewanella oneidensis for enhanced uranium adsorption: Elucidating the role of exogenous AHLs and validation in actual uranium-contaminated groundwater

Large quantities of low-concentration uranium-contaminated water from the nuclear industry poses a critical environmental challenge due to the limitations of current methods on removal efficiency and adsorption selectivity. This study developed a novel biofilm cathode for enhanced uranium adsorption by leveraging the quorum sensing (QS) system of Shewanella oneidensis MR-1. Biofilm formation was induced using exogenous acyl-homoserine lactones (AHLs), with C4-HSL (10 μmol/L) identified as the most efficient signal molecule. It significantly improved biofilm properties, increasing thickness by 107.7 % versus the control without AHLs, boosting extracellular protein content, and increasing the proportion of living cells. Microstructure analysis (CLSM) revealed a “base-polysaccharide-gel” three-dimensional structure, where proteins, lipids, and β-polysaccharides form a functional gel layer that provides the primary functional matrix for uranium binding. The C4-HSL-induced biofilm exhibited a 43.4 % higher reduction peak current and a 33.3 % decrease in electron transfer resistance, confirming improved electron transfer efficiency. Furthermore, coupling CLSM, SEM-EDS, FT-IR and XPS analysis indicated uranium capture was primarily dominated by complexation/coordination with functional groups on extracellular polymeric substances (EPS), supplemented by electrochemical reduction of 25.91 % soluble U(VI) to insoluble U(IV). Accordingly, a possible mechanism model of QS-driven biofilm cathode is proposed for optimizing biofilm structure and enhancing uranium capture. Finally, verification tests in actual uranium-contaminated groundwater demonstrated the biofilm cathode exhibited exceptional performance with a 99.4 % uranium recovery rate and high selectivity (K d,U at 34.57 L/g). These findings highlight the significant potential of AHLs-triggered QS as a powerful strategy to optimize bioelectrochemical properties for highly-efficient uranium remediation and resource recovery.