Efficient removal of antibiotic ciprofloxacin by catalytic wet air oxidation using sewage sludge-based catalysts: degradation mechanism by DFT studies
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2023
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Elsevier
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Gutiérrez-Sanchez P, Álvarez-Torrellas S, Larriba M, Gil MV, Garrído Zoido JM, Garcia J. Efficient removal of antibiotic ciprofloxacin by catalytic wet air oxidation using sewage sludge-based catalysts: Degradation mechanism by DFT studies. J Environ Chem Eng. 2021 April 11(2):109344
Abstract
In this work, the sewage sludge-derived activated carbon (SAC) loaded with iron nanoparticles (FeSAC) showed a highly effective catalytic activity in the degradation of the antibiotic ciprofloxacin by the CWAO reaction. The properties of FeSAC catalyst were studied by using N2 adsorption-desorption measurements at 77 K, scanning electron microscopy, X-ray fluorescence spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. The CWAO reaction was evaluated at different temperatures (120–140 ºC), total pressure (10–30 bar) and catalyst doses (0.1–0.7 g/L) in a batch reactor. In this regard, temperature and catalyst dosage showed a significant impact on the removal of the tested antibiotic. By using a catalyst dose of 0.7 g/L, ciprofloxacin degradation and CO2 selectivity were higher than 99 % and 60 %, respectively, and were achieved within two hours at 140 °C and 20 bar. The loss of the active phase (Fe) of the catalyst in the reaction medium was measured, obtaining negligible values (less than 24 ppb). This catalyst showed high stability under the tested reaction conditions. In addition, a potential equation was proposed to correctly describe the evolution of ciprofloxacin degradation. The calculated activation energy of the CWAO process was 53.8 kJ/mol. Additionally, Density Functional Theory (DFT) calculations were performed to illustrate the degradation mechanism of ciprofloxacin, where the electronic energies indicated the compounds that are most difficult to degrade by CWAO. Finally, a proof of concept using an environmentally-relevant matrix was carried out, verifying the technical feasibility of the synthesized catalyst for its application with more complex matrices, consecutive reaction cycles and at a low treatment cost
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This work has been supported by the Spanish MICINN through the project CATAD3.0 PID2020–116478RB-I00. In addition, the authors thank the financial support from the Comunidad de Madrid (Spain) through the Industrial PhD projects (IND2017/AMB-7720 and IND2019/AMB-17114), REMTAVARES Network (S2018/EMT-4341) and the European Social Fund. MVG also thanks Grant PID2021-125295OB-I00 funded by MCIN/AEI/ 10.13039/501100011033 and by “ERDF A way of making Europe” and the Junta de Extremadura and the European Regional Development Fund (ERDF/FEDER), through Grant No. GR21039. The authors are grateful for the Supercomputer facility LUSITANIA funded by CenitS and the Computaex Foundation.