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Photocatalytic degradation of acetaminophen and caffeine using magnetite–hematite combined nanoparticles: kinetics and mechanisms

Abstract

The increased use of pharmaceutical and personal care products (PPCPs) has contributed to the contamination of water systems and put pressure on the development of new techniques to deal with this problem. Acetaminophen (paracetamol), a common analgesic and antipyretic drug, and caffeine, a known central nervous system stimulant, are being used frequently by many people and found in large amounts in wastewater systems. In this work, their removal, by photocatalytic degradation, was promoted using magnetic nanoparticles (NPs) based on iron oxides. Besides being obtained from cheap and plentiful source, the magnetic properties of these NPs provide an easy way to separate them from the solution when the reaction is complete. Three types of hematite-based NPs, one pure (1) and two of them composed by a magnetite core partially (2) or completely (3) covered by a hematite shell, were synthesized and characterized. Sample 2 was the best photocatalyst for both pollutants’ photo-assisted degradation. Under UV-vis irradiation and using a 0.13 g catalyst/L solution, the total acetaminophen and caffeine degradation (20 ppm/150 mL) was achieved in 45 min and 60 min, respectively. The identification of some of the intermediate products was carried out by liquid chromatography in combination with electrospray ionization mass spectrometry. A complementary Density Functional Theory (DFT) study revealed the relative stability of several species formed during the acetaminophen and caffeine degradation processes and gave some insight about the most favorable degradation pathways.

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Data availability

All data generated or analyzed during this study are included in this published article and its supplementary information files.

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Acknowledgments

We thank Ms. A. Dias for the LC-MS(±) experimental assistance.

Funding

This work was supported by the Fundação para a Ciência e a Tecnologia (FCT) through projects PEst-OE/FIS/UI0261/2014, PEst-OE/MULTI/UI0612/2013, UIDB/04046/2020 and UIDP/04046/2020, UIDB/00100/2020 and UIDP/00100/2020, Lisboa-01-2020, and 0145FEDER-022125-IST/RNEM. TAF thanks CQB and FCT for a fellowship (PEst-OE/MULTI/00612/2013). AG is thankful to the FCT for the awarded project PTDC/QUI-QFI/29236/2017 and the PEst-OE/MULTI/00612/2013 grant.

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Authors and Affiliations

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Contributions

Tiago A. Fernandes: conceptualization, investigation, formal analysis, visualization, and writing of the original draft; Sofia G. Mendo: investigation and formal analysis; Liliana P. Ferreira: investigation, methodology, formal analysis, and visualization; Nuno R. Neng: methodology and formal analysis; M. Conceição Oliveira: resources, methodology, and formal analysis; Adrià Gil: investigation, methodology, formal analysis, visualization, and writing of the original draft; Maria Deus Carvalho: conceptualization, formal analysis, and writing of the original draft; Olinda C. Monteiro: conceptualization, resources, writing of the original draft, and review and editing; José M. F. Nogueira: resources and methodology; Maria José Calhorda: conceptualization, methodology, visualization, supervision, and writing (review and editing). All authors have given approval to the final version of the manuscript.

Corresponding author

Correspondence to Maria José Calhorda.

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The authors declare that they have no competing interests.

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Responsible Editor: Sami Rtimi

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Supplementary information

ESM 1

†Electronic Supplementary Information (ESI) contains: magnetic behavior of samples 2 and 3 (Fig. S1), linearized plot for the photocatalytic degradation for APAP and CAF (Figs. S2 and S3), repetitive APAP photodegradation during 5 cycles runs (Fig. S4), electronic spectra of APAP photodegradation and CAF photodegradation (Fig. S5), LC-ESI(+)/MS2 of APAP (Figs. S6-S11) and CAF adducts (Figs. S13-S16), and DFT calculated fragmentation pathways of APAP (Fig. S12) and CAF (Fig. S17). (DOCX 1.56 mb).

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Fernandes, T.A., Mendo, S.G., Ferreira, L.P. et al. Photocatalytic degradation of acetaminophen and caffeine using magnetite–hematite combined nanoparticles: kinetics and mechanisms. Environ Sci Pollut Res 28, 17228–17243 (2021). https://doi.org/10.1007/s11356-020-12016-z

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  • DOI: https://doi.org/10.1007/s11356-020-12016-z

Keywords

  • Photocatalysis
  • Acetaminophen
  • Caffeine
  • Degradation
  • Magnetic nanoparticles
  • DFT calculations