Concentrating versus non-concentrating reactors for solar photocatalytic degradation of p-nitrotoluene-o-sulfonic acid

The photocatalytic oxidation of the non-biodegradable p-nitrotoluene-o-sulf onic acid (p-NTS) in homogeneous (photo-Fenton reactions) and heterogeneous (with TiO2) solutions has been studied at a pilot-scale under solar irradi ation at the Plataforma Solar de Almeria (PSA). In this study two different reactors were tested: a medium concentrating radiation system (Heliomans, HM) and a non-concentrating radiation system (CPC). Their advantages and di sadvantages for p-NTS degradation have been compared and discussed. The deg radation rates obtained in the CPC collector are around three times more ef ficient than in the HM collectors. However, in both systems, 100% of the in itial concentration of p-NTS was removed. Kinetic experiments were performe d in both systems using TiO2 suspensions. During the photodegradation, the disappearance of p-NTS was followed by HPLC, the mineralization of the solu tion by the TOC technique, the evolution of NO3-, NO2- and SO4= concentrati on by ionic chromatography, the toxicity by the standard Microtox (R) test, and the biodegradability by BOD, and COD measurements. The obtained result s demonstrated the utility of the heterogeneous catalysis (using TiO2 as ca talyst) as a pretreatment method that can be followed by a biological proce ss.