Environmental remediation by an integrated microwave/UV illumination technique: IX. Peculiar hydrolytic and co-catalytic effects of platinum on the TiO2 photocatalyzed degradation of the 4-chlorophenol toxin in a microwave radiation field

The photocatalyzed degradation of the 4-chlorophenol toxin (4-CP) in aqueous naked TiO2 and platinized TiO2 suspensions simultaneously subjected to UV light and microwave radiation was revisited to examine the fate of this toxin in the microwave-assisted photocatalytic process by monitoring loss of total organic carbon (TOC; mineralization), formation of chloride ions (dechlorination of 4-CP), and identification of intermediates using HPLC and electrospray mass spectral (LC–MSD) techniques. Attempts are made to delineate microwave thermal and nonthermal factors that impinge on the degradation by comparing experimental results from microwave-generated heat versus results from a conventional (externally heated) thermally-assisted process, and from results in which the thermal factors were minimized by examining the degradative process at constant ambient temperature (25 °C). Possible microwave radiation effects on the Pt co-catalyst supported on TiO2 were also probed through comparison of the degradation of 4-CP occurring on Pt/TiO2 and on naked TiO2 photocatalysts. Results suggest that, in a microwave radiation field, naked TiO2 and Pt/TiO2 particle surfaces interact with the microwaves. The degradation pathway exhibited characteristics of hydrolysis of reactants and intermediates. Nonthermal microwave effects play a role in the overall degradative process occurring in platinized TiO2 dispersions. The possible nature of these unusual microwave effects is briefly discussed.