Nanosilver-impregnated and acid-treated vermiculite within water filtration system and its dual function in bacterial disinfection and silver reabsorption

Antibacterial activity of silver-impregnated vermiculite and silver removal capability of acid-treated vermiculite (Verm-A) were assessed through ۴-stage water filtration systems. The antibacterial vermiculite was prepared through cation exchange process in silver nitrate solutions of ۰, ۵۰۰, ۱۰۰۰, and ۲۰۰۰ mgl-۱, named Verm-B۰, Verm-B۵۰۰, Verm-B۱۰۰۰, and Verm-B۲۰۰۰, respectively. The Verm-A was only treated with ۱ M HCl to increase its negative zeta potential. Bacterium Aeromonas hydrophila was inoculated into the filtration systems and then total colony forming units in water samples was enumerated for ۹۶ h. Flame atomic absorption spectrometer showed the maximum silver adsorption (۴۹.۱۷ mg/g) by Verm-B۲۰۰۰. Scanning electron microscopy micrographs illustrated silver with nano dimension crystallites with the average sizes of ۲۷۴.۸۰۸, ۱۹۴, ۱۶۲.۲۵۸ nm on the surface of Verm-B۲۰۰۰, Verm-B۵۰۰, and Verm-B۱۰۰۰, respectively. All the Verm-B products were approved to possess a strong antibacterial activity, with reducing the bacterial growth over ۹۵% in all of the filtration systems containing Verm-B۵۰۰-۲۰۰۰. The highest log reduction value of ۳.۴۷ CFU mL-۱ at ۹۶ h was observed for the filtration system containing Verm-B۱۰۰۰. The percentage of silver released from the total Ag in Verm-B۵۰۰ was ۳۲.۳۶%, Verm-B۱۰۰۰ ۲۷.۸۷%, and Verm-B۲۰۰۰ ۱۷.۲۴%; of these amounts, ۹۰.۹%, ۸۱.۸%, and ۷۵.۷% were reabsorbed respectively, by Verm-A. The observed bactericidal efficiency could open an avenue to use silver-impregnated vermiculite in water treatment. Moreover, acid treated vermiculite could be introduced as an affordable absorbent for removal of silver from water filtration system, industrial wastewater and reduce metallic environmental contaminants.

کلیدواژه ها:

Silver nanoparticles ، Vermiculite ، Antibacterial ، Water purification ، Silver removal