Insights into solar photo-Fenton process using iron(III)–organic ligand complexes applied to real textile wastewater treatment

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2015-04, Vol.266, p.203-212
• Main Authors: Manenti, Diego R., Soares, Petrick A., Módenes, Aparecido N., Espinoza-Quiñones, Fernando R., Boaventura, Rui A.R., Bergamasco, Rosângela, Vilar, Vítor J.P.
• Format: Article
• Language: English
• Subjects: Biodegradability enhancement; Ferric–organic ligand complexes; Solar radiation; Textile wastewaters
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2014.12.077

•Solar photo-Fenton reactions were applied to the real textile wastewater treatment.•Conventional photo-Fenton reaction showed limited efficiency in the mineralization.•Photo-Fenton reaction mediated by ferric–organic ligands complexes was evaluated.•Optimal operating condition for solar-ferrioxalate-photo-Fenton process was assessed.•Ferrioxalate-photo-Fenton oxidations improve the biodegradability index of effluent. The treatment of a real textile wastewater was accomplished using a conventional photo-Fenton reaction and mediated by different ferric–organic ligand complexes, performed in lab and pilot scale photoreactors irradiated by simulated and natural solar radiation, respectively. The textile wastewater presents a dark-blue colour, alkaline pH, a high organic content (COD=1239mgO2L−1; DOC=408mgCL−1) and moderate biodegradability (BOD5/COD=0.16). The conventional solar-photo-Fenton reaction showed limited efficiency in the mineralization of the textile wastewater, which is characterized by a fast initial dissolved organic carbon decay in the absence of light, mainly attributed to the formation of iron–organic pollutants complexes with a low solubility at acidic pH values, leading to iron precipitation, followed by a very slow reaction rate under UV–visible light associated to (i) low amounts of dissolved iron and (ii) low photoactivity of the iron precipitates. The addition of the organic ligands, such as oxalic acid, citric acid and EDDS, enhanced significantly the photo-Fenton reaction, avoiding the formation of iron–organic pollutants complexes, and consequently increase of the quantum yield for ferrous ions production through the photodecarboxylation of ferric–organic ligands complexes. The catalytic activity of the iron–organic ligand complexes increased in the following order: Fe(III)–EDDS