Date of Award

12-1-2013

Degree Type

Dissertation

University or Center

Clark Atlanta University(CAU)

Degree Name

Ph.D.

Department

Chemistry

First Advisor

Eric A. Mintz Ph.D.

Abstract

Photocatalytic inactivation of microorganisms by titanium dioxide (TiO2) is being studied as a water treatment technology. When TiO2 absorbs light, electrons (e~) and positive holes (h*) are formed inside the crystals that can migrate to the surface of TiO2- As a result, reactive oxygen species (ROS) such as O2'" and OH' are generated to damage microorganisms. The objective of this work was to investigate the effect of bicarbonate ion, both added and formed upon the photocatalytic oxidation of substrates, on TiO2 photocatalytic activity on the inactivation of viruses and enzymes, and the oxidation of proteins and amino acids. We examined the TiO2 photocatalytic inactivation of MS2, a single stranded RNA bacterial phage used as a model for human enteric viruses, and adenovirus, a double stranded DNA human enteric virus. Three proteins, P-galactosidase an enzyme that catalyzes the breakdown of lactose into galactose and glucose, Bovine Serum Albumin, a well-known transporter protein derived from the blood plasma of cows, and a tetrapeptide were examined. The kinetics of photocatalytic T1O2 oxidation of alanine, aspartic acid, cysteine, phenylalanine, serine, and tyrosine were also studied. These experiments were conducted in sterile water with and without added bicarbonate and in some cases in the presence of Ca** to remove bicarbonate formed in solution by photocatalytic oxidation of the substrate.

We have found that bicarbonate considerably enhanced TiO>2 photocatalytic activity on the organism, protein, and amino acid levels due to CO3"" which was generated as a secondary radical by OH' reacting with the carbonate/bicarbonate ions present in our system. The CO3'\ a selective oxidant with longer life time, was more effective during photocatalytic treatment when compared to the highly reactive but non selective OH*. Therefore this knowledge can be used to enhance the photodegradation ofwastewater.

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