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<div>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<br></div>

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In the photo-chemical conversion of hydrogen peroxide (H2O2) into radical ⦁OH, the impact of radiation dose (the quantum yield) on the oxidation kinetics has been properly reported, whereas the H2O2 dose is mostly treated as an attempt-and-error variable. This present work formally analyses the oxidant dose in terms of the efficiency of ⦁OH consumption by the micropollutant mineralization, which ultimately enables a generalist strategy for more cost-effective dosimetry of the oxidant. The experimental timedependent measure of two reagents (pollutant and oxidant) and one product (CO2) enables assessment to the micro-kinetics from the perspective of the chemical dynamic. The analysis was demonstrated for photo-Fenton (FP) oxidation of hydrochlorothiazide (HCT) using a tubular photo-reactor and UVA radiation. The average value of ~ 38% was on top of the best efficiencies in association with some of the fastest rates of mineralization. Such efficiencies are demonstrated to depend on the stochiometric concentration of the oxidant. Here, the variable stoichiometric H2O2 excess for mineralization is proposed as a universal metric to quantify the (under-) over-dose of H2O2. Overall, H2O2 excess between 2 and 5 leads to H2O2 consumption efficiencies above 30% together with a fast rate of CO2 formation (mineralization), whereas any value below 1 invariably leads to a sluggish oxidation rate, leading even to the full depletion of the oxidant. Aside from proposing a selection criterion for the most cost-effective H2O2dose and providing some examples, this work carefully analyzes the commitment of the H2O2 excess with respect to the energy costs (EEO).

<div>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<br></div>