Photodegradation studies of carbaryl pesticides were performed as a function of solar concentration using newly designed CPC collectors with different geometric solar concentration ratios. Design of a Multiple Compound Parabolic Concentrator, or MCPC, was performed by taking into account both that photocatalytic degradation efficiency is a function of the square root of photon flow intensity that excites the photocatalyst and that TiO2 is able to absorb more sunlight (photons) than the provided in utilising a 1-sun geometric concentration ratio (CR). The Multiple Compound Parabolic Concentrator was initially designed to carry out photocatalytic degradation studies as a function of geometric solar concentration ratio between 1 sun and 2 suns and subsequently to explore the possibility of using CPC collectors in photocatalysis studies with a solar concentration ratio greater than 1 sun. TiO2 photocatalysts, immobilised over 1.40-meter-long Duran glass tubes, were specially fabricated for this experiment. Finally, to evaluate the photoreactor performance, the photocatalytic degradation of the carbaryl pesticide was used carried out. When the photocatalytic reactor equipped with the CPC solar concentrator of 1 sun was used to carry out degradation processes under UV + TiO2 and UV + TiO2 + H2O2 conditions, degradation levels of 41% and 79% were reached, respectively. Alternatively, when the photocatalytic reactor equipped with the CPC solar concentrator of 2 suns was used to degrade the same pollutant under the same conditions, degradation levels of 54% and 92% were achieved, respectively. To complete the characterisation of the above mentioned degradation processes, the experimental values of parameters such as global kinetic constants, TOC and COD, were determined. (C) 2015 Elsevier Ltd. All rights reserved.