Although the photocatalytic activity of TiO2 polymorphs and hexagonal
ZnO is well studied with artificial UV light sources, however, their efficacy is not
well examined in natural sunlight exposure. In the current study, the photocatalytic
activity of the polymorphs of TiO2 (rutile and anatase) and hexagonal ZnO
was evaluated in sunlight exposure for the removal of resonance stabilized 2-, and
4- derivatives of chloro and nitrophenol isomers and compared with that of P-25.
The polymorphs of TiO2 and hexagonal ZnO, after synthesis by sol-gel and hydrogel
routes, were subjected to optical, structural and morphological characterization.
The hexagonal ZnO exhibited significantly higher as compared to anatase
and rutile polymorphs but comparable with that of P-25 in sunlight illumination.
For the hexagonal ZnO, the ring opening route of degradation mediated by superoxide anion radicals
was confirmed by the absence of non-hydroxylated aromatic intermediates whereas the contribution
of both superoxide anion radicals and hydroxyl radicals was evidenced for the TiO2 polymorphs and
P-25. The kinetics of the degradation/mineralization of substrates was also compared.
Keywords: Chlorophenols, nitrophenols, P-25, Sunlight photocatalysis, TiO2 Polymorphs, ZnO.
Rights & PermissionsPrintExport