AuthorSjogren, Jon Charles.
Committee ChairSierka, Raymond A.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractViral disinfection by near-UV photocatalysis was accomplished in aqueous titanium dioxide suspensions. A photocatalyzed inactivation of phage MS2 of 90% increased to 99.9% after 2 μM Fe (from ferrous sulfate) was added to phosphate-buffered, distilled water containing TiO₂ and 20 μM Tris hydrochloride. Iron additions ranging from 0.2 to 20 μM, showed that a 2 μM Fe concentration produced maximum photoreactivity. The initial rate of MS2 inactivation, in the solution without iron, increased more than twenty-fold when Tris was absent. This rate of inactivation showed an additional nine-fold increase when the MS2 was photocatalyzed in a sample of Tucson groundwater, primarily because of low concentrations of groundwater species that scavenge hydroxyl radicals. A 99.997% inactivation of MS2 was observed after a 1000-ml glass beaker, containing a 100-ml suspension of MS2-spiked groundwater and 1 g l⁻¹ TiO₂, was exposed to sunlight for 10 sec. The hydroxyl radical (OH⋅) was linked to the MS2 destruction by verifying the ability of OH⋅ to inactivate MS2, and by demonstrating that OH⋅ was produced during the photocatalyzed reactions. An OH⋅ source, and competition kinetics techniques, were used to obtain these findings and to produce other evidence of MS2 inactivation by photocatalytically-produced OH⋅. These methods were also used to show that the presence of 2 μM Fe increased the quantity of liquid-phase OH⋅ that was produced during photocatalysis. Measurements showed that most of the added 2 μM Fe partitioned onto the TiO₂ surface, allowing the opportunity for OH⋅ production by Fenton reactions. Experimental results were consistent with proposed photocatalytic mechanisms (involving photocatalysis, diffusion, and Fenton reaction) by which OH⋅ was available on and off the TiO₂ surface. Non-OH⋅ means of MS2 inactivation were evaluated. The MS2 inactivation that occurred in unilluminated solutions to which Fe and TiO₂ were added, was probably caused by the effects of stirring, oxidation by iron, and MS2 enmeshment in aggregating TiO₂ particles.
Degree ProgramChemical and Environmental Engineering