Plasma treated activated carbon impregnated with silver nanoparticles for improved antibacterial effect in water disinfection

A strategy to selectively attach more Ag nanoparticles on the external surface of activated carbon (AC) is being proposed and used as an antibacterial medium for water disinfection. Ag nanoparticles were first synthesized under UV irradiation by reducing silver nitrate with sodium citrate; the latter serving the dual purpose of both a reducing and a capping agent. Transmission electron micrographs show that Ag particles have a mean diameter of 28 nm with a standard deviation of 5 nm. The AC was treated by an oxygen plasma to increase the number of polar functional groups on the surface. This carbon-surface modification treatment increased the number of Ag nanoparticles on the external surface of AC, compared to that inside pores. Fourier transform infra-red and X-ray photoelectron spectroscopy results show that the oxygen plasma treatment leads to an increase in oxygen-containing-functional groups, such as C-O and CO, from 21.9% to 30.8%. Microbiological investigations by plate assay and shake flask tests confirmed the antibacterial nature of the AC-Ag hybrid, showing an order of magnitude increase in death rate constant from 3.72 to 41.88 h−1 on plasma treatment (rate constant means rate of loss of viable cell).