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<p>Emergent compounds (ECs), such as pharmaceuticals, persist in natural waters due to the inefficiency of conventional wastewater treatments. Ozonation is a promising tertiary treatment, yet its large-scale application faces challenges, particularly regarding reactor design and mass transfer efficiency. This study investigates the impact of reactor dimensions (varying the internal diameter – D<sub>i</sub> and the height – H), mass transfer efficiency at five different ozone flow rates (Q<sub>O3</sub>) and operational conditions (pH, Time and Q<sub>O3</sub>) for degradation (%D) and mineralization (%M) of caffeine (CAF), and the volumetric mass transfer coefficient of ozone (O<sub>3</sub>) in the liquid phase (k<sub>La</sub>). Results showed that the reactor dimensions significantly influence process efficiency, with D<sub>i</sub> having a greater impact, particularly on CAF degradation. The selected reactor (D<sub>i</sub> = 3.5&#xa0;cm and H = 15&#xa0;cm) achieved high process efficiency (%D = 41.50 and %M = 14.64) with k<sub>La</sub> = 0.0425&#xa0;s<sup>−1</sup>. The mass transfer efficiency was enhanced at Q<sub>O3</sub> = 0.6 L.min<sup>−1</sup> (%O<sub>3 Consumed(10 min)</sub> = 25.10 and %T<sub>O3(10 min)</sub> = 30.34), achieving values of k<sub>La</sub> (0.0947&#xa0;s<sup>−1</sup>) up to 286% higher than those reported in similar systems, while higher flow rates of Q<sub>O3</sub> = 0.8 and 1.0 L.min<sup>−1</sup> reduced the process efficiency. A dome-shaped diffuser drastically decreased k<sub>La</sub> (0.0141&#xa0;s<sup>−1</sup>). Under optimal conditions (pH = 12, Time = 30&#xa0;min and Q<sub>O3</sub> = 0.6 L.min<sup>−1</sup>) CAF degradation and mineralization reached 100% and 84.29%, respectively, reducing TOC from 28.21 to 4.43&#xa0;mg.L<sup>−1</sup>. Finally, through the toxicity assessment, via quantitative structure–activity relationship (QSAR), indicated that the oxidation by-products were less toxic than the parent compound. Thus, this study underscores the importance of optimizing reactor design and operational parameters to enhance ozonation efficiency, enabling sustainable and cost-effective large-scale implementation without additional equipment and/or reagents, thereby minimizing losses.</p> Graphical Abstract <p></p>

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Optimized Ozonation of Caffeine Targeting its Mineralization: Reactor Design and Environmental Safety Insights

  • 期刊论文

  • 发表日期：

    2025年6月4日

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  • Júlia Toffoli de Oliveira,
  • Letícia Reggiane de Carvalho Costa,
  • Caroline Borges Agustini,
  • Liliana Amaral Féris

摘要

Emergent compounds (ECs), such as pharmaceuticals, persist in natural waters due to the inefficiency of conventional wastewater treatments. Ozonation is a promising tertiary treatment, yet its large-scale application faces challenges, particularly regarding reactor design and mass transfer efficiency. This study investigates the impact of reactor dimensions (varying the internal diameter – Di and the height – H), mass transfer efficiency at five different ozone flow rates (QO3) and operational conditions (pH, Time and QO3) for degradation (%D) and mineralization (%M) of caffeine (CAF), and the volumetric mass transfer coefficient of ozone (O3) in the liquid phase (kLa). Results showed that the reactor dimensions significantly influence process efficiency, with Di having a greater impact, particularly on CAF degradation. The selected reactor (Di = 3.5 cm and H = 15 cm) achieved high process efficiency (%D = 41.50 and %M = 14.64) with kLa = 0.0425 s−1. The mass transfer efficiency was enhanced at QO3 = 0.6 L.min−1 (%O3 Consumed(10 min) = 25.10 and %TO3(10 min) = 30.34), achieving values of kLa (0.0947 s−1) up to 286% higher than those reported in similar systems, while higher flow rates of QO3 = 0.8 and 1.0 L.min−1 reduced the process efficiency. A dome-shaped diffuser drastically decreased kLa (0.0141 s−1). Under optimal conditions (pH = 12, Time = 30 min and QO3 = 0.6 L.min−1) CAF degradation and mineralization reached 100% and 84.29%, respectively, reducing TOC from 28.21 to 4.43 mg.L−1. Finally, through the toxicity assessment, via quantitative structure–activity relationship (QSAR), indicated that the oxidation by-products were less toxic than the parent compound. Thus, this study underscores the importance of optimizing reactor design and operational parameters to enhance ozonation efficiency, enabling sustainable and cost-effective large-scale implementation without additional equipment and/or reagents, thereby minimizing losses.

Graphical Abstract