Rapid measurement of photocatalytic oxidation of poly(vinyl chloride) by in situ FTIR spectrometry of evolved CO₂

The CO 2 generated by UV irradiation of unplasticised PVC pigmented with TiO 2 was monitored by in situ Fourier transform infrared (FTIR) spectrometry. CO 2 was evolved immediately irradiation began (although no HCl was detected) and when irradiation ceased CO 2 evolution fell significantly. A comparison of photogeneration of CO 2 from unpigmented and pigmented PVC demonstrated that, although a heavily coated TiO 2 (R5) did not increase the rate of CO 2 formation, lightly coated TiO 2 (R3) photocatalysed PVC oxidation to CO 2 . As expected for a photocatalytic process, the photogeneration of CO 2 increased with increased TiO 2 loading. The convenience of the FTIR method allowed the increased rate of oxidation with increasing partial pressure of oxygen, or increasing humidity, to be demonstrated. It was also shown that the rate of photocatalytic oxidation varied as the square root of UV intensity. This dependence would result if recombination of UV generated charge carriers controls the rate of photocatalysis.