Heterogeneous photocatalytic oxidation of polyvinyl alcohol in water

Titanium dioxide mediated photocatalytic degradation of polyvinyl alcohol (PVA) was studied in an annular photoreactor with two 6 W (Emax=365 nm) UV lamps as light source. In the presence of both TiO2 and light, and initial concentration of 30 mg/l, 55.3% of PVA was found to degrade after an hour. The effects of initial concentration, pH and the addition of H2O2 on the rate of degradation of PVA were studied. The results showed that it was more effective for PVA to be degraded under acidic or alkaline condition. The order of reaction rates was pH 10>pH 9>pH 4>pH 5>pH 7. Proper amount of H2O2 could improve the photodegradation rate of PVA. However, the further increase of H2O2 might inhibit the system efficiency. Fourier transformed infrared spectroscopy (FTIR) indicated that several carboncarbon bonds were scissored, which led to the formation of short-chain compounds during the photocatalytic oxidation of PVA. These intermediates were also degraded with prolonged reaction.