Photocatalytic degradation of poly(bisphenol-A-carbonate) in solution over combustion-synthesized $TiO_2$: mechanism and kinetics

Nano-sized, high surface area$TiO_2,$ synthesized by a solution combustion method,was employed for the photodegradation of poly(bisphenol- A-carbonate) in solution. The products formed during degradation were detected using UV-Vis spectroscopy, FT–IR and GC/MS. The mechanism of breakage during photocatalytic degradation can be attributed to concerted rearrangement (Photo-Fries) and non-concerted cage recombination (oxidation). The degradation was followed by determining the molecular weight distribution using gel permeation chromatography (GPC) and modeled with continuous distribution kinetics. The mode of breakage was purely by random chain scission and showed the presence of weak and strong photodegradable links. The presence of combustion-synthesized $TiO_2$ catalyst did not alter the degradation mechanism but increased the degradation rates by an order of magnitude compared to the photodegradation rate. However, the presence of commercial Degussa P-25 catalyst did not cause a significant increase in degradation rates compared to the photodegradation rate. The higher photoactivity of combustion-synthesized $TiO_2$ compared to that of Degussa P-25 for the photodegradation of polycarbonate may be due to reduced band-gap, higher hydroxyl content, higher surface area, nano-size and crystallinity of the combustion-synthesized $TiO_2.