Effect of two types of reflective surfaces with different geometry in a solar pilot plant for the photocatalytic degradation of RB5 dye using a TiO ₂ /rGO nanocomposite

Abstract The degradation of Reactive Black 5 (RB5) dye in a solar pilot plant has been compared where reflective surfaces were added to the reactor to increase solar irradiation. Taking the tubular reactor as a reference, the effect of adding two types of reflective surfaces with different geometry was analyzed: one of the surfaces consisted of composite parabolic concentrators (CPCs) and the other of a flat reflective surface placed under the tube array. Photocatalytic reaction conditions were considered, with TiO 2 and the TiO 2 /rGO nanocomposite as photocatalysts, as well as without catalyst under photolysis conditions. A pseudo first order kinetic model was used to interpret the results, a function of the intensity of solar irradiation and the area of the tube irradiated, both directly and reflected. To estimate the area of the reactor irradiated by the reflecting surfaces, the ray tracing technique was used. For both catalysts, the highest degradation rates occurred in the presence of CPC-type surfaces. From the apparent kinetic constants, an increase of about 11 % was found for the presence of the flat reflective plate and up to 65 % for the CPC, both with respect to the tubular reactor and nanocomposite material. Based on ray tracing analysis, and according to solar time, the active area reflecting rays on the surface of the reactor was, for the CPC, in the order of 50 % greater than that of the flat reflective plate, which was consistent with the kinetic results between both systems.