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Iohexol degradation in wastewater and urine by UV-based Advanced Oxidation Processes (AOPs): Process modeling and by-products identification

Giannakis, Stefanos, Jovic, Milica, Gasilova, Natalia, Pastor Gelabert, Miquel, Schindelholz, Simon, Furbringer, Jean-Marie, Girault, Hubert, Pulgarin, César
Journal of environmental management 2017 v.195 pp. 174-185
absorbance, acidification, byproducts, chemical oxygen demand, high performance liquid chromatography, iron, models, oxidation, transmittance, urine, wastewater
In this work, an Iodinated Contrast Medium (ICM), Iohexol, was subjected to treatment by 3 Advanced Oxidation Processes (AOPs) (UV, UV/H2O2, UV/H2O2/Fe2+). Water, wastewater and urine were spiked with Iohexol, in order to investigate the treatment efficiency of AOPs. A tri-level approach has been deployed to assess the UV-based AOPs efficacy. The treatment was heavily influenced by the UV transmittance and the organics content of the matrix, as dilution and acidification improved the degradation but iron/H2O2 increase only moderately. Furthermore, optimization of the treatment conditions, as well as modeling of the degradation was performed, by step-wise constructed quadratic or product models, and determination of the optimal operational regions was achieved through desirability functions. Finally, global chemical parameters (COD, TOC and UV-Vis absorbance) were followed in parallel with specific analyses to elucidate the degradation process of Iohexol by UV-based AOPs. Through HPLC/MS analysis the degradation pathway and the effects the operational parameters were monitored, thus attributing the pathways the respective modifications. The addition of iron in the UV/H2O2 process inflicted additional pathways beneficial for both Iohexol and organics removal from the matrix.