  Citation: Gomes, J.; Bernardo, C.; Jesus, F.; Pereira, J.L.; Martins, R.C. Ozone Kinetic Studies Assessment for the PPCPs Abatement: Mixtures Relevance. ChemEngineering 2022, 6, 20. https://doi.org/10.3390/ chemengineering6020020 Academic Editor: Andrew S. Paluch Received: 26 January 2022 Accepted: 23 February 2022 Published: 1 March 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). chemengineering Article Ozone Kinetic Studies Assessment for the PPCPs Abatement: Mixtures Relevance João Gomes 1, * , Carla Bernardo 1 ,Fátima Jesus 2 , Joana Luísa Pereira 3 and Rui C. Martins 1 1 CIEPQPF—Chemical Engineering Processes and Forest Products Research Center, Department of Chemical Engineering, Faculty of Sciences and Technology, University of Coimbra, Rua Sílvio Lima, 3030-790 Coimbra, Portugal; carla_1997@live.com.pt (C.B.); martins@eq.uc.pt (R.C.M.) 2 CESAM—Centre for Environmental and Marine Studies, Department of Environment and Planning, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal; fatima.jesus@ua.pt 3 CESAM—Centre for Environmental and Marine Studies, Department of Biology, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal; jpereira@ua.pt * Correspondence: jgomes@eq.uc.pt; Tel.: +351-239-798-723 Abstract: The increasing consumption of pharmaceutical and personal care products (PPCPs) by humankind has been causing an accumulation of contaminants (commonly referred to as contam- inants of emerging concern), in effluents and water resources. Ozonation can be used to improve the removal of these contaminants during water treatment to alleviate this burden. In this work, the degradation of methyl (MP), propylparaben (PP), paracetamol (PCT), sulfamethoxazole (SMX), and carbamazepine (CBZ) by ozonation was assessed both for individual compounds and for mix- tures with increasing complexity (two to five compounds). Ozonation was performed at pH3 to gain an insight on the exclusive action of molecular ozone as oxidizing agent. The degradation of contaminants was described as a function of time and transferred ozone dose, and the corresponding pseudo-first order kinetic rate constants (k’) were determined. PPCPs were degraded individually within 1.5 to 10 min. CBZ was the most quickly degraded (k’ = 1.25 min −1 ) and MP the most resistant to ozone (k’ = 0.25 min −1 ). When in the mixture, the degradation rate of the contaminants was slower. For parabens, the increase of the number of compounds in the mixture led to an exponential decrease of the k’ values. Moreover, the presence of more PPCPs within the mixture increased energy consumption associated with the treatment, thereby reflecting higher economic costs. Keywords: ozonation; kinetics studies; contaminants of emerging concern; energy consumption; by-products 1. Introduction Drinking water is one of the most important resources for the humankind [1]. Cur- rently, drinking water scarcity is a major concern, as it affects both public health and the economy [2]. The exponential population growth, increased industry development, and consequent effects concerning climate change have been leading to an increased water demand across the planet [1]. It is expected that the demand for affordable and reliable water to support economic development will grow to about 40% by 2030 [3]. In a more favorable scenario, but nonetheless still concerning one, Boretti and Rosa [4] reported that global water demand is expected to have an increase of up to 20–30% by 2050. Therefore, wastewater reclamation is important issue to face and the impact of water scarcity must be minimized. Within this perspective, wastewater treatment plants (WWTP) need to improve their effectiveness regarding the removal of contaminants of emerging concern (CECs), such as the pharmaceutical and personal care products (PPCP), with the addition of efficient tertiary processes [2,5]. Every day, industries, agriculture, and even the general population use water and then release numerous compounds into wastewater. These pollutants enter the water cycle and ChemEngineering 2022, 6, 20. https://doi.org/10.3390/chemengineering6020020 https://www.mdpi.com/journal/chemengineering