Silver-embedded granular activated carbon as an antibacterial medium for water purification

Silver (Ag) particle embedded granular activated carbon (GAC) was made for the first time to assess its ability in inhibiting the growth of Escherichia coli (E. coli), a water-borne bacterial pathogen. Ag-GAC was made by impregnating GAC with AgNO3 and then reducing it to metallic Ag. Plate assay showed slight inhibition of E. coli, even with Ag-GAC prepared from 0.005 mol L-1 AgNO3, but this and shake flask tests showed a conspicuous effect only for higher concentrations of 0.1-1 mol L-1 AgNO3. Flow tests further indicated that Ag-GAC made from 1.0 mol L-1 AgNO3 caused a desirable three orders of reduction in E. coli number concentration in less than 30 s. An optimum of 9-10.5 wt% of embedded Ag in the final Ag-GAC product was necessary for the requisite complete inhibition of E. coli, killing bacteria in the contact-mode for up to 350 L of flowing water. These results prove that Ag-GAC possesses antibacterial properties and can be used for disinfection to produce potable quality water. (C) 2008 Society of Chemical Industry.