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

Abstract

The CO₂ generated by UV irradiation of unplasticised PVC pigmented with TiO₂ was monitored by in situ Fourier transform infrared (FTIR) spectrometry. CO₂ was evolved immediately irradiation began (although no HCl was detected) and when irradiation ceased CO₂ evolution fell significantly. A comparison of photogeneration of CO₂ from unpigmented and pigmented PVC demonstrated that, although a heavily coated TiO₂ (R5) did not increase the rate of CO₂ formation, lightly coated TiO₂ (R3) photocatalysed PVC oxidation to CO₂. As expected for a photocatalytic process, the photogeneration of CO₂ increased with increased TiO₂ 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.

Keywords:

• PVC
• PHOTODEGRADATION
• CO2
• TIO2
• FTIR