Abstract
In this work, primidone, a high persistent pharmacological drug typically found in urban wastewaters, was degraded by different ozone combined AOPs using TiO2 P25 and commercial WO3 as photocatalyst. The comparison of processes, kinetics, nature of transformation products, and ecotoxicity of treated water samples, as well as the influence of the water matrix (ultrapure water or a secondary effluent), is presented and discussed. In presence of ozone, primidone is rapidly eliminated, with hydroxyl radicals being the main species involved. TiO2 was the most active catalyst regardless of the water matrix and the type of solar (global or visible) radiation applied. The synergy between ozone and photocatalysis (photocatalytic ozonation) for TOC removal was more evident at low O3 doses. In spite of having a lower band gap than TiO2 P25, WO3 did not bring any beneficial effects compared to TiO2 P25 regarding PRM and TOC removal. Based on the transformation products identified during ozonation and photocatalytic ozonation of primidone (hydroxyprimidone, phenyl-ethyl-malonamide, and 5-ethyldihydropirimidine-4,6(1H,5H)-dione), a degradation pathway is proposed. The application of the different processes resulted in an environmentally safe effluent for Daphnia magna.
Highlights
IntroductionPresent in waters at very low concentrations (μg L−1 or ng L−1 ), pharmaceuticals, personal care products, pesticides, etc., may cause adverse effects on aquatic organisms due to their toxicity and/or mutagenicity and/or endocrine disruptor character [1,2,3]
Present in waters at very low concentrations, pharmaceuticals, personal care products, pesticides, etc., may cause adverse effects on aquatic organisms due to their toxicity and/or mutagenicity and/or endocrine disruptor character [1,2,3]. Most of these compounds known as contaminants of emerging concern (CEC) are not regulated, many of them being recalcitrant towards the classical operations applied in urban wastewater treatment plants (UWWTP)
This high degradation rate was unexpected considering the low reactivity of PRM towards ozone, and that at the pH of the solution the decomposition of O3 into HO· was not favored
Summary
Present in waters at very low concentrations (μg L−1 or ng L−1 ), pharmaceuticals, personal care products, pesticides, etc., may cause adverse effects on aquatic organisms due to their toxicity and/or mutagenicity and/or endocrine disruptor character [1,2,3]. UWWTP effluents have been identified as the primary source of CEC in the environment [4]. Before the discharge or reuse of the effluents, the application of a tertiary treatment such as ozonation, activated carbon adsorption, membrane filtration, or advanced oxidation processes (AOPs) is highly recommended [5]. The key point to evaluate the efficacy of an AOP is the ability to mineralize the organics present in the water matrix
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