The role of TiO2 photocatalyst in degradation of halogenated phenols: Experimental, DFT and antibacterial study

Degradation of industrial pollutants 4-chlorophenol and 4-bromophenol by heterogeneous photocatalysis using TiO2 nanoparticles of different sizes and allotropes was investigated. Physicochemical properties of a wide range of TiO2 nanoparticles were correlated with their photocatalytic activity. The increase in anatase particle size led to an enhancement of the halophenols degradation rate, oppositely to rutile. EPR measurements and experiments using radical scavenger showed that depending on anatase nanoparticles size, different reactive species domi-nated halophenols degradation. Based on DFT modeling, alternative degradation pathways were proposed, leading to hydroxylation of halophenol aromatic ring or to direct decarboxylation. Antibacterial activity of nanoparticles, 4-chlorophenol and degradation intermediates was investigated. Changes in toxicity during the photocatalytic process were evaluated. Our results demonstrate that not only crystalline form and/or morphology of the photocatalyst, but also other properties as well as treatment duration are important pa-rameters in its performance and should be considered in the development of photocatalytic applications.