Photocatalytic oxidation of acetonitrile in aqueous suspension of titanium dioxide irradiated by sunlight

The photocatalytic oxidation of acetonitrile (CH3CN) was carried out in aqueous suspensions of polycrystalline TiO2 P25 Degussa irradiated by sunlight. A plug flow photoreactor in a total recycle loop was used for carrying out reactivity experiments in which the concentrations of acetonitrile, of its intermediate oxidation products and of not-purgeable organic carbon (NPOC) were monitored. The influence of the presence of strong oxidant species (H2O2, S2O82-, ClO-) on the process rate was studied. The dependence of acetonitrile photo-oxidation rate on the substrate concentration and on the catalyst amount was also investigated. The photodegradation rate of substrate and NPOC followed first order kinetics with respect to acetonitrile and NPOC concentrations, respectively. The presence of S2O82- and solar irradiation determined the occurrence of homogeneous degradation of acetonitrile and NPOC. In the presence of irradiated catalyst, a significant synergetic effect was observed for NPOC degradation while for the acetonitrile oxidation this effect was not evident. H2O2 did not affect the process while ClO- affected negatively the acetonitrile oxidation rate and it inhibited the NPOC degradation. (C) 2002 Elsevier Science Ltd. All rights reserved.