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Stoichiometric Excess of H2O2 as Strategy of Oxidant Dosing for Intensifying Both Degradation and Mineralization of the Hydrochlorothiazide via UVCH2O2, Dark-Fenton, and Photo-Fenton
preprintsubmitted on 12.10.2020, 13:16 and posted on 13.10.2020, 10:04 by Fernando J. Cunha-Filho, Andressa Mota-Lima, claudio A. Oller do Nascimento, Osvaldo Chiavone-Filho
Hydrochlorothiazide (HCT) is a pharmaceutical micropollutant highly toxic to the environment, being strictly mandatory to oxidize it completely toward CO2. In this context, how could the HCT oxidation via advanced oxidative processes benefit from the accelerated oxidation rates promoted by the mineralization stoichiometric excess of H2O2 ? Overall, this work elucidates the role of stoichiometric H2O2 concentration on promoting fast degradation/mineralization rates across Advanced Oxidative Processes (AOP). Employing 0.68 excess of H2O2, it was found absolute (100%) HCT degradation within 60 minutes and 95% within 30 min for UVC-H2O2 oxidation; however, the mineralization of HCT suffered limited optimization even at high H2O2 excess, being at the best performance 26.76% HCT mineralized via UVC photo-Fenton within 60 min at initial 2.00 H2O2 excess. Very presumably, the evaporation of H2O2 was the underlying reason for a low mineralization performance. Together with a detailed mathematical methodology, the time-synchronized evolution of both the residual H2O2 concentration and the TOC depletion were employed to infer the quantity of radical ∙OH that effectively was consumed by the micropollutant mineralization. The global mean efficiency of radicals •OH consumption by the HCT mineralization laid around 15% for UVC Fenton considering H2O2 excess of 2.00. Under these conditions, the residual H2O2 concentration depletes significantly within 30 minutes of UVC photo-Fenton oxidation, which indicates that either the solution heating or stirring is very likely to promote a substantial loss of H2O2 by evaporation in the beaker-assembled reactor