Open Access
Magnetically recyclable TiO2/MXene/MnFe2O4 photocatalyst for enhanced peroxymonosulphate-assisted photocatalytic degradation of carbamazepine and ibuprofen under simulated solar light
(Elsevier, 2023) Grzegórska, Anna; Ofoegbu, Joseph Chibueze; Cervera Gabalda, Laura María; Gómez Polo, Cristina; Sannino, Diana; Zielinska-Jurek, Anna; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
In this study, a novel TiO2/Ti3C2/MnFe2O4 magnetic photocatalyst with dual properties, enabling (i) improved photocatalytic degradation with PMS activation under simulated solar light and (ii) magnetic separation after the degradation process in an external magnetic field was developed and applied for the efficient photodegradation pharmaceutically active compounds (PhACs) frequently present in wastewater and surface waters worldwide. MXene was used as a Ti precursor for anatase/rutile synthesis and as a co-catalyst in the photodegradation process. Manganese ferrite with ferrimagnetic properties was coupled with the TiO2/Ti3C2 composite to facilitate the magnetic separation after the purification process in an external magnetic field. Moreover, MnFe2O4 was used for PMS activation, producing •SO4- radicals with a strong oxidation ability and higher redox potential of 2.5–3.1 V (vs. NHE) than •OH radicals with a standard oxidation–reduction potential of 2.8 V. The effect of the manganese ferrite content in the composite structure (5 wt% and 20 wt%) on the physicochemical properties and photocatalytic activity of the magnetic photocatalyst was investigated. Furthermore, the most photocatalytic active composite of TiO2/MXene/5%MnFe2O4 was used for peroxymonosulphate-assisted photocatalytic degradation of ibuprofen and carbamazepine. The effect of peroxymonosulphate concentration (0.0625 mM, 0.125 mM, and 0.25 mM) and the synergistic effect of PMS activation on photocatalytic degradation was studied. Based on the obtained results, it was found that TiO2/MXene/5%MnFe2O4/PMS process is an efficient advanced treatment technology for the oxidation of emerging contaminants that are not susceptible to biodegradation. Carbamazepine and ibuprofen were completely degraded within 20 min and 10 min of the PMS-assisted photodegradation process under simulated solar light. The trapping experiments confirmed that •SO4- and •O2- are the main oxidising species involved in the CBZ degradation, while •SO4- and h+ in the IBP degradation. Furthermore, introducing interfering ions of Na+, Ca2+, Mg2+, Cl-, and SO42– in the model seawater did not affect the removal efficiency of both pharmaceuticals. In terms of reusability, the performance of the TiO2/MXene/5%MnFe2O4/PMS photocatalyst was stable after four subsequent cycles of carbamazepine and ibuprofen degradation.
Open Access
Magnetic-field-assisted photocatalysis of N-TiO2 nanoparticles
(IEEE, 2023-09-04) Cervera Gabalda, Laura María; Garayo Urabayen, Eneko; Beato López, Juan Jesús; Pérez de Landazábal Berganzo, José Ignacio; Gómez Polo, Cristina; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
Nitrogen doped TiO2 nanoparticles were synthesized through solvothermal method employing Ti (IV) butoxide and HNO3 as precursors. Structural and optical characterizations confirm their nanometer nature (sizes around 10 nm) and the band-gap energy values in the UV range (3.2 eV). Nitrogen doping enhances the occurrence of optical Urbach tails extending towards the visible region. Visible photocatalytic performance (degradation of methyl orange) is correlated with maximum values in the magnetic susceptibility linked to a magnetic polarization of the anatase structure via defects (oxygen vacancies). The application of magnetic field provides a positive effect (acceleration in reaction kinetics) within the UV-Vis range.
Open Access
Improved photocatalytic and antibacterial performance of Cr doped TiO2 nanoparticles
(Elsevier, 2021) Gómez Polo, Cristina; Larumbe Abuin, Silvia; Gil Bravo, Antonio; Muñoz Labiano, Delia; Rodríguez Fernández, L.; Fernández Barquín, Luis; García-Prieto, Ana; Fernández-Gubieda, María Luisa; Muela, Alicia; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
The effect of Cr and N doping in the adsorption capacity, photocatalytic properties and antibacterial response of TiO2 anatase nanoparticles is analyzed. The nanoparticles (N-TiO2, Cr-TiO2 and Cr/N-TiO2) were prepared by the sol-gel method. The structural (X-ray diffraction and TEM) and magnetic (SQUID magnetometry) characterization confirms the nanosized nature of the anatase nanoparticles and the absence of secondary phases. The enhancement of the adsorption capacity of the dye (methyl orange) on the surface of the catalysts for the Cr and Cr/N doped samples, together with the redshift of the UV-Vis absorbance spectra promote a high photocatalytic performance under visible light in these nanocatalysts. The culturability and viability of the Escherichia coli DH5α in a medium supplemented with the nanoparticles was characterized and compared with the evolution under visible light (both without and with nanoparticles). The results show that Cr-TiO2 nanoparticles under visible light display antibacterial activity that cannot be accounted by the toxicity of the nanoparticles alone. However the antibacterial effect is not observed in N-TiO2 and Cr/N-TiO2. The differences in the electrostatic charge (isoelectric point) and the degree of nanoparticle dispersion are invoked as the main origins of the different antibacterial response in the Cr-TiO2 nanoparticles.
Open Access
Synthesis, characterization, and application of 2D/2D TiO2-GO-ZnFe2O4 obtained by the fluorine-free lyophilization method for solar light-driven photocatalytic degradation of ibuprofen
(Springer, 2022) Malinowska, Izabela; Kubica, Pawel; Madajski, Piotr; Ostrowski, Adam; Gómez Polo, Cristina; Carvera, Laura; Bednarski, Waldemar; Zielinska-Jurek, Anna; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
In this study, we report the potential of 2D/2D TiO2-GO-ZnFe2O4 photocatalyst obtained using the fluorine-free lyophilization technique for the degradation of ibuprofen belonging to the group of active pharmaceutical ingredients (API). The improved ibuprofen degradation under simulated solar light was achieved in the presence of a composite of 2D TiO2 combined with GO and embedded ZnFe2O4, which additionally provides superparamagnetic properties and enables photocatalyst separation after the photodegradation process. After only 20 min of the photodegradation process in the presence of 2D/2D TiO2-GO-ZnFe2O4 composite, more than 90% of ibuprofen was degraded under simulated solar light, leading to non-toxic and more susceptible to biodegradation intermediates. At the same time, photolysis of ibuprofen led to the formation of more toxic intermediates. Furthermore, based on the photocatalytic degradation analysis, the degradation by-products and possible photodegradation pathways of ibuprofen were investigated. The photodegradation tests and electronic spin resonance analyses indicated the significant involvement of superoxide radicals and singlet oxygen in the ibuprofen photodegradation process.
Open Access
Modulating photocatalytic activity of nitrogen doped TiO2 nanoparticles via magnetic field
(Elsevier, 2024-07-30) Gómez Polo, Cristina; Cervera Gabalda, Laura María; Garayo Urabayen, Eneko; Beato López, Juan Jesús; Pérez de Landazábal Berganzo, José Ignacio; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The effect of the magnetic field on the photocatalytic activity of TiO2-based nanoparticles is analyzed using a magnetically-assisted photoreactor with permanent magnets to generate a controlled uniform magnetic field, B (¿82 mT). Nitrogen doped TiO2 nanoparticles (sizes around 10 nm) were synthesized through a solvothermal method employing Ti(IV) butoxide and HNO3 (x = 0, 0.5, 1, 1.5 and 2 mL) as precursors and their structural, optical and magnetic properties were analyzed. Specifically, nitrogen doping is confirmed through Hard X-ray Photoelectron Spectroscopy (HAXPES) in those samples synthesized with low HNO3 concentrations (x = 0.5, 1). The correlation between spin polarization (magnetic susceptibility) and visible photocatalytic activity (methyl orange as a model organic pollutant) is particularly analyzed. Surprisingly, opposite effects of the magnetic field on the photocatalytic performance are found in the visible range (above 400 nm) or under UV-Vis irradiation (decrease and increase in the photocatalytic activity, respectively, under magnetic field). The Langmuir-Hinshelwood model allows us to conclude that the strong decrease in adsorption under the magnetic field (around 42 % for x = 0.5) masks the increase in the kinetic constant (close to 58 % for x = 0.5) related mainly to the effect of Lorentz forces on the reduction of the electron-hole recombination.