Photocatalytic degradation and mineralization of bisphenol A by TiO2 and platinized TiO2

Bisphenol A (BPA) was degraded photocatalytically by different TiO2 photocatalysts at pHs 3 and 10. It was found that the mineralization of BPA showed a stronger dependence on the pH and different oxidation products were detected during BPA degradations at pHs 3 and 10. At pH 3, 20 ppm of BPA was completely mineralized into CO2 after 120 min of UV illumination. However, only 20–30% of the carbon from the BPA was converted into CO2 for the same illumination time at pH 10. This observation indicated that intermediates formed from degradation at pH 10 are very stable to further photocatalytic oxidation while those intermediates formed at pH 3 are more susceptible to degradation and mineralization. Although the oxidation intermediates obtained from BPA degradation at pH 10 were more difficult to be degraded, Microtox® toxicity analyses revealed that for all tested photocatalysts, these intermediates were less toxic compared to the parent BPA molecule. As a result, a gradual decrease in toxicity was found for BPA degradation at pH 10. On the contrary, more toxic intermediates were generated during the early stage of BPA oxidation when the experiment was performed at pH 3. In addition, platinization was found to increase the rates of BPA degradation and mineralization. When platinum was loaded (0.2–1.0 wt.%) onto the surface of TiO2, the rates of degradation and mineralization were increased 3–6 times. Nevertheless, the existence of platinum deposits did not show any effects on the distribution of intermediate compounds formed from BPA degradation.