Virus inactivation by silver doped titanium dioxide nanoparticles for drinking water treatment Michael V. Liga a , Erika L. Bryant b , Vicki L. Colvin b , Qilin Li a, * a Department of Civil and Environmental Engineering, Rice University, 6100 Main St., Houston, TX 77005, United States b Department of Chemistry, Rice University, 6100 Main St., Houston, TX 77005, United States article info Article history: Received 16 June 2010 Received in revised form 4 September 2010 Accepted 13 September 2010 Available online 19 September 2010 Keywords: Drinking water Nanotechnology Photocatalysis Silver Titanium dioxide Virus abstract Photocatalytic inactivation of viruses and other microorganisms is a promising technology that has been increasingly utilized in recent years. In this study, photocatalytic silver doped titanium dioxide nanoparticles (nAg/TiO 2 ) were investigated for their capability of inactivating Bacteriophage MS2 in aqueous media. Nano-sized Ag deposits were formed on two commercial TiO 2 nanopowders using a photochemical reduction method. The MS2 inactivation kinetics of nAg/TiO 2 was compared to the base TiO 2 material and silver ions leached from the catalyst. The inactivation rate of MS2 was enhanced by more than 5 fold depending on the base TiO 2 material, and the inactivation efficiency increased with increasing silver content. The increased production of hydroxyl free radicals was found to be responsible for the enhanced viral inactivation. ª 2010 Elsevier Ltd. All rights reserved. 1. Introduction The removal of viruses and other pathogens from drinking water (and the environment in general) is important for the maintenance of the health and well being of society. Patho- genic viruses such as adenovirus, norovirus, rotavirus, and hepatitis A commonly occur in both surface and groundwater sources (Abbaszadegan et al., 2003; Hamza et al., 2009; Wong et al., 2009) and must be effectively inactivated to provide safe water. In the United States just between 2003 and 2005 there were four reported waterborne disease outbreaks attributed to viruses in drinking water affecting 282 people (US Centers for Disease Control and Prevention, 2006, 2008). The USEPA requires treatment systems capable of providing 4 log (99.99%) removal of viruses for all surface water sources (US Environmental Protection Agency, 2006a) and groundwater sources with a history of contamination or other deficiencies (US Environmental Protection Agency, 2006b). Traditional chlorine disinfection, while highly effective for viral inactivation, produces harmful disinfection byproducts (DBPs) when organic compounds are present in the water. This has prompted stricter regulations concerning the acceptable levels of these compounds (US Environmental Protection Agency, 2006c). Although UV disinfection has not been found to form DBPs (Liberti et al., 2003), some viruses such as adenoviruses are highly resistant to UV disinfection (Yates et al., 2006). As a result, the USEPA has increased the UV fluence requirements for 4 log removal of viruses from 40 mJ/cm 2 to 186 mJ/cm 2 (US Environmental Protection Agency, 2006a). The new high fluence requirement signifi- cantly increases the energy demand, which translates into a higher treatment cost. * Corresponding author. Tel.: þ1 713 348 2046. E-mail address: qilin.li@rice.edu (Q. Li). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/watres water research 45 (2011) 535 e544 0043-1354/$ e see front matter ª 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2010.09.012