Study On The Photocatalytic Degradation Of Biomolecules

Semiconductor photocatalysis is a novel technology for the treatment of environmental pollutions in recent years. This new technology attracts much attention for its lots of advantages: complete oxidation of almost all organic pollutants, no secondary pollution and the direct utilization of solar energy. Ever since Matsunaga reported the bactericidal effect of TiO2 in 1985, attention has been paid to photocatalytic technology in the application of sterilization. In this study, bovine serum albumin (BSA) and phosphatidylcholine (PC) were selected as model compounds to study the photodegradation of two important components of virus, ie, protein and phosphatidycholine by the photocatalysts. High performance liquid chromatogram (HPLC), Fourier-transform infrared spectra (FTIR), ultraviolet visible spectra (UV-Vis), time-resolved fluorescent spectra were used to monitor the photocatalytic processes. The effects of photocatalysts loading, calcinations temperature, specific surface areas and surface charge states on the photocatalytic efficiency were also investigated. The following results were obtained: (1) Under UV illumination, BSA could be completely degraded by TiO₂ in 5 h. However it could only be partly degraded under UV illumination and no degradation of BSA was observed on TiO₂ only; (2) BSA could be completely mineralized to CO₂ and inorganic comounds after 40 h photocatalytic treatment; (3) Photocatalysts loading, calcinations temperature and reaction acidity can significantly influence the photodegradation efficiency; (4) The surface charge states of the photocatalysts played an important role in the photodegradation process by influencing the adsorption of BSA on the surface of photocatalysts. At pH range between 4.74 (the isoelectric point of BSA) and 6.4 (the isoelectric point of TiO2 calcined at 400℃), higher absorption of BSA on the photocatalyst surface was found and led to a higher photocatalytic efficiency; (5) The photocatalytic degradation of PC on TiO₂ film was significantly affected by the way the film was prepared, the substrates, the reaction atmosphere and the light source. Best activity was observed on the films prepared by electrophoresis. The photocatalytic activity was higher in the existence of O₂ compared to that in N₂. Although the bactericidal effect of photocatalysts has been well documented, to our knowledge this is the first time that the photocatalytic degradation of biomolecules was systematic investigated. Our results can be useful for a better understanding of the bactericidal mechanism of photocatalysis and in the developing of broad-spectrum, high effective and environmental friendly antivirus agents based on photocatalysis.