Advanced chemical oxidation of reactive dyes in simulated dyehouse effluents by ferrioxalate-Fenton/UV-A and TiO2/UV-A processes

Effective degradation of various mono- and bifunctional aminochlorotriazine reactive dyes in simulated dyehouse wastewater was achieved by the application of ferrioxalate-photo-Fenton [Fe(C2O4)(3)(3-) -/H2O2/UV-A; 300 nm > lambda > 400 nm] and titanium dioxide-mediated heterogeneous photocatalytic (TiO2/UV-A) treatment processes. These so-called advanced oxidation processes were studied in a novel batch photoreactor that was irradiated by a solar simulating installation. DL colorization by the ferrioxalate-photo-Fenton oxidation process was found to proceed three times faster than the photocatalytic process, while the latter was more efficient in reducing the optical density at 280 nm wavelength (UV280nm). Complete decolourization and partial mineralization with 17-23% total organic carbon (TOC) and 73-86% UV280nm removals were achieved by the ferrioxalate-Fenton/UV-A and TiO2/UV-A processes, respectively, within a I-h treatment time. Emphasis was placed on the effect of dyehouse effluent strength on decolourization kinetics, along with possible advantages of the ferrioxalate-Fenton/UV-A process over the conventional photo-Fenton (Fe2+/H2O2/UV-C) process. The results of these experiments showed that the more dilute the dyehouse effluent the faster the decolourization rate. On the basis of spectrophotometric measurements, dye decomposition could be successfully fitted to the empirical Langmuir-Hinshelwood kinetic model. (C) 2000 Elsevier Science Ltd. All rights reserved.