Photocatalytic degradation of metoprolol tartrate in suspensions of two TiO 2-based photocatalysts with different surface area. Identification of intermediates and proposal of degradation pathways

This study investigates the efficiency of the photocatalytic degradation of metoprolol tartrate (MET), a widely used β 1-blocker, in TiO 2 suspensions of Wackherr's " Oxyde de titane standard" and Degussa P25. The study encompasses transformation kinetics and efficiency, identification of intermediates and reaction pathways. In the investigated range of initial concentrations (0.01-0.1mM), the photocatalytic degradation of MET in the first stage of the reaction followed approximately a pseudo-first order kinetics. The TiO 2 Wackherr induced a significantly faster MET degradation compared to TiO 2 Degussa P25 when relatively high substrate concentrations were used. By examining the effect of ethanol as a scavenger of hydroxyl radicals (OH), it was shown that the reaction with OH played the main role in the photocatalytic degradation of MET. After 240min of irradiation the reaction intermediates were almost completely mineralized to CO 2 and H 2O, while the nitrogen was predominantly present as NH4+. Reaction intermediates were studied in detail and a number of them were identified using LC-MS/MS (ESI+), which allowed the proposal of a tentative pathway for the photocatalytic transformation of MET as a function of the TiO 2 specimen

Photocatalytic degradation of metoprolol in water suspension of TiO2 nanopowders prepared using sol-gel route

Nanocrystalline titanium dioxide (TiO2) powders have been synthesized by sol-gel method using titanium tetrachloride (TiCl4) or tetrabutyl titanate (Ti(OC4H9)(4) as precursors, different alcohols and calcination temperatures in the range from 400 to 650 A degrees C. The photocatalytic activity of as-prepared powders has been tested for the degradation of metoprolol tartrate salt, a selective beta-blocker used to treat a variety of cardiovascular diseases, and compared to photocatalytic activity obtained from Degussa P25. Nanosized TiO2 powders prepared from TiCl4 and amyl-alcohol, calcined at 550 A degrees C, displayed an activity comparable to Degussa P25, whereas the sample from the same series, calcined at 650 A degrees C, showed higher photocatalytic activity in the whole range of the catalyst loading. Structural, morphological and surface properties of synthesized TiO2 nanopowders have been investigated by XRD, SEM, EDS and BET measurements, as well as FTIR and Raman spectroscopy, in order to find out the material properties which enable rapid an efficient decomposition of metoprolol under UV radiation