Enhancement of the oxidative removal of diclofenac and of the TiO2 rate of photon absorption in dye-sensitized solar pilot scale CPC photocatalytic reactors

The sensitization of rate of photon absorption of a TiO2 photocatalyst irradiated by natural solar radiation in pilot scale compound parabolic collectors (CPC's) photoreactors was investigated. Methyl red (MR) dye was used as a photo-sensitizer to increase the rate of photon absorption of a TiO2 photocatalyst and the oxidative removal of the common pharmaceutical diclofenac (DCF) in solar, pilot scale, compound parabolic collectors (CPC's) photoreactors. The impact of the concentrations of TiO2 and MR were investigated and tuned to determine the most effective operational conditions. The results show that the dye-sensitization process of the catalyst and the degra- dation of DCF were favored at catalyst concentrations close to the optimum. Complete degradation and min- eralization of DCF DCF were achieved under most effective operational conditions. The mineralization of DCF and dye increased by up to 65% in the presence of the MR sensitizer compared to the results without sensitizer. The oxidation by-products formed during the process were identified by gas chromatography-mass spectrometry (GC-MS). A detailed mechanism of the dye-sensitization process was proposed, and a kinetic model for the simul- taneous degradation of diclofenac and the dye was derived using the pseudo-stationary state method. This study demonstrates the positive impact of dye sensitizers on the photocatalytic degradation of pharmaceuticals in pilot scale photoreactors irradiated by natural sunlight.