Novel antimicrobial filtering materials based on carvacrol, eugenol, thymol and vanillin immobilized on silica microparticles for water treatment

Abstract The objective of this work was to develop filtering materials based on different-sized silica particles functionalized with carvacrol (0.01 g/g SiO2), eugenol (0.04 g/g SiO2), thymol (0.01 g/g SiO2) and vanillin (0.12 g/g SiO2). The removal capability of the functionalized supports was evaluated using distilled water inoculated with Escherichia coli (104 CFU/mL). Water samples (100 mL) were filtered through layers of supports of different thickness (0.5, 1 or 1.5 cm thick), according to different filtration tests. The results showed the supports' efficacy, because the microorganism was totally eliminated after filtration, requiring the passage of the sample through the filter only a few seconds in some cases. Removal of E. coli was due to a combination of physical adsorption and inactivation on contact with the immobilized molecules. Functionalized supports' efficacy remained after filtering multiple samples and/or pre-conditioning (washing with 1–3 L of sterile water), which suggests the maintenance of the molecules attached to silica microparticles' surface. No wash-out effect was determined after filtration with eugenol, thymol and vanillin functionalized supports, which demonstrated the covalent immobilization of antimicrobial compounds. Industrial relevance Ensuring appropriate water decontamination with no potential health risks associated with conventional chemical disinfectants and meeting the growing point-of-use water treatment demand require emerging technologies for the microbial decontamination of drinking water. The developed filtering materials showed good bacterial removal capacity with log reduction values of 104 CFU/mL, which are adequate for household water treatment technologies. As proof-of-concept, this study demonstrated the high potential of the developed functionalized silica supports to remove bacteria such as E. coli in water treatment.