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

- 3 UV-based AOPs were used to degrade the ICM Iohexol in aqueous matrices.
- UV was the driving force of the degradation process, but without causing mineralization.
- 2nd degree modeling and optimization of the treatment was performed for used AOPs.
- The degradation pathway and the operational parameters' effect were identified.
- Adding Fe2+ and H2O2 is recommended for pollutant mineralization enhancement.

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.

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