Advanced water treatment with antimicrobial silver-lignin nanoparticles sonochemically-grafted on cork granulates in activated carbon packed-bed columns

Cork biomass (C) was grafted with antimicrobial silver phenolated-lignin nanoparticles (AgPLN) using a fast and simple sono-enzymatical process. The AgPLN-functionalised cork (C-AgPLN) exhibited potent antibacterial and antibiofilm properties against the common waterborne pathogens, Escherichia coli and Staphylococcus aureus. Its effects on bacterial cells included alterations in cell morphology and structure, as revealed by electron microscopy (SEM and TEM) and fluorescence microscopy (LIVE/DEAD staining). These effects also included increased oxidative stress (80 % and 31 % in E. coli and S. aureus, respectively), >99 % reduction in viability, a 60 % reduction in E. coli biofilm, and a 44 % reduction in S. aureus biofilm, as quantified by spectroscopic methods (ROS measurement, XTT metabolic activity test, and crystal violet staining). C-AgPLN also demonstrates anti-quorum sensing properties against both Gram-negative and Gram-positive bacteria, crucial for disrupting bacterial communication, thereby preventing biofilm formation. Further, C-AgPLN was combined with activated carbon (AC) at different proportions (1 %, 2 %, and 4 % w/w) in lab-scale packed-bed columns for the disinfection of water contaminated with E. coli or S. aureus. Columns containing 4 % w/w C-AgPLN demonstrated 100 % disinfection efficiency after 1 h of operation in recirculation mode (flow rate = 8.6 mL/min), and were reusable for up to 2 and 4 cycles without losing their disinfection capacity. Noteworthy, silver ion (Ag⁺) release was not detected in the effluent after 240 h columns operation (ICP-MS detection limit of <0.07 μg/L), confirming the environmental safety on the novel water-disinfection approach. Given that adsorption is a well-established method for advanced wastewater treatment, these results underscore the potential of nano-enabled AC-packed columns for safely and efficiently controlling the spread of water-associated pathogens.