Photocatalytic properties of Zr-doped titania in the degradation of the pharmaceutical ibuprofen

Zr-doped titania of anatase structure type has been prepared by a combined sol–gel and chemical vapour deposition (CVD) process. The material has been characterized by XRD, TEM and chemical analysis. The photocatalytic performance has been investigated in the oxidative decomposition of the pharmaceutical ibuprofen (IBP) down to low ppm concentrations. The change of the composition of the reaction solution after photocatalytic treatment was followed by UV–Vis spectroscopy and GC/MS. Formation of reaction intermediates was studied by HPLC coupled electrospray ionization time-of-flight mass spectrometry ESI-TOF-MS. The catalytic performance has been studied by varying the catalyst and substrate concentration as well as changing the catalyst-to-substrate ratio. The influence of pH, adsorption and re-use of the catalyst has been tested. The results confirm the high catalytic activity of Zr-doped titania compared to pure titania at low catalyst loading. The material shows the improved textural mesoporosity. However, more reaction intermediates were formed, leading to faster deactivation of the photocatalyst. ESI-TOF-MS measurements point to the formation of a couple of reaction intermediates, which poison the catalyst.