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 pi- lot 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) pho- toreactors. 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.