Titanium Dioxide Nanoparticle Photocatalysed Degradation of Ibuprofen and Naproxen in Water: Competing Hydroxyl Radical Attack and Oxidative Decarboxylation by Semiconductor Holes

Romeiro, Andreia; Azenha, M. Emília; Canle, Moisés; Rodrigues, V. H.; Silva, José Paulo da

doi:10.1002/slct.201801953

Cited by 33 publications

(18 citation statements)

References 92 publications

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“…In the latter, photoelectrons are transferred from impregnated TiO2-P25 VB to Cu or V 3d-orbitals lying just below of the CB, then migrate to form O2 -radicals, whereas holes migrate to the surface, react with HOrendering HO radicals, then the so-formed radicals are able to initiate the degradation of the adsorbed phenol molecules (Figure 9). Metal ions with charge different than Ti 4+ could produce oxygen vacancies in the lattice with energy levels below the TiO2-P25 CB (Figure 9), allowing visible light harvesting, acting as active sites for adsorbed water dissociation and capturing holes to diminish electron-hole recombination, thus enhancing the photocatalytic activity [35,[66][67]. Photocatalytic activity, among other factors, is not only dependent on the photogenerated charge carriers trapping, efficient detrap to the surface should also occur.…”

Section: Photodegradation Of Phenol Under Vis and Uv Light Irradiationmentioning

confidence: 99%

Improved Photocatalyzed Degradation of Phenol, as a Model Pollutant, over Metal-Impregnated Nanosized TiO2

Belekbir¹,

Azzouzi²,

Hamidi³

et al. 2020

Nanomaterials

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Photocatalyzed degradation of phenol in aqueous solution over surface impregnated TiO2 (M = Cu, Cr, V) under UV-Vis (366 nm) and UV (254 nm) irradiation is described. Nanosized photocatalyts were prepared from TiO2-P25 by wet impregnation, and characterized by X-ray diffraction, X-ray fluorescence, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy, Raman spectroscopy, and adsorption studies. No oxide phases of the metal dopants were found, although their presence in the TiO2-P25 lattice induces tensile strain in Cu-impregnated TiO2-P25, whereas compressive strain in Cr- and V-impregnated TiO2-P25. Experimental evidences support chemical and mechanical stability of the photocatalysts. Type IV N2 adsorption–desorption isotherms, with a small H3 loop near the maximum relative pressure were observed. Metal surface impregnated photocatalysts are mesoporous with a similar surface roughness, and a narrow pore distribution around ca. 25 Å. They were chemically stable, showing no metal lixiviation. Their photocatalytic activity was followed by UV-Vis spectroscopy and HPLC–UV. A first order kinetic model appropriately fitted the experimental data. The fastest phenol degradation was obtained with M (0.1%)/TiO2-P25, the reactivity order being Cu > V >> Cr > TiO2-P25 under 366 nm irradiation, while TiO2-P25 > Cu > V > Cr, when using 254 nm radiation. TOC removal under 366 nm irradiation for 300 min showed almost quantitative mineralization for all tested materials, while 254 nm irradiation for 60 min led to maximal TOC removal (ca. 30%). Photoproducts and intermediate photoproducts were identified by HPLC–MS, and appropriate reaction pathways are proposed. The energy efficiency of the process was analysed, showing UV lamps are superior to UVA lamps, and that the efficiency of the surface impregnated catalyst varies in the order Cu > V > Cr.

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Section: Photodegradation Of Phenol Under Vis and Uv Light Irradiationmentioning

confidence: 99%

Improved Photocatalyzed Degradation of Phenol, as a Model Pollutant, over Metal-Impregnated Nanosized TiO2

Belekbir¹,

Azzouzi²,

Hamidi³

et al. 2020

Nanomaterials

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“…This material has been used as a titania standard photocatalyst. Indeed, Evonik P25 remains the most used and efficient photocatalyst under UV light on a large range of molecules [25][26][27][28]. This material is prepared by an aerosol process which involves high temperature treatments (1000-1300 °C) [26].…”

Section: Introductionmentioning

confidence: 99%

Ambient temperature ZrO2-doped TiO2 crystalline photocatalysts: Highly efficient powders and films for water depollution

Mahy

Lambert

Tilkin

et al. 2019

Materials Today Energy

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In this paper, several TiO2 materials doped with zirconia precursor (0.7, 1.4, 1.6 and 2.0 mol%) were synthesized by an easy aqueous sol-gel synthesis at ambient temperature. This method consisted in the peptization of the TiO2 colloid in presence of HNO3. The corresponding pure TiO2 material was also synthesized for comparison. The performances and the physicochemical properties of these materials were compared to the well-known Evonik P25 photocatalyst.The physico-chemical characterizations showed that nano-crystalline anatase-brookite particles were produced with the sol-gel process, with higher specific surface area than P25 (~ 200 m 2 g -1 vs. 47 m 2 g -1 ). All samples presented a higher visible absorption than P25. The XPS spectra showed that all the samples were doped with nitrogen and that mixed TiO2-ZrO2 oxide materials were obtained when doping with zirconia precursor.Photoactivity was evaluated through the degradation of p-nitrophenol in water. On the one hand, under UV/visible light, the ZrO2 doping increased the degradation efficiency of the pure TiO2 catalyst due to a better charge separation in the mixed TiO2-ZrO2 oxides. The activity of the sample with the highest dopant content was even higher than the one of P25. On the other hand, under visible light, all samples were much more efficient than P25. This activity shift towards visible range was due to the N-doping of the catalysts, with a slight improvement for the doped ones.Finally, the feasibility of producing films starting from an aqueous suspension of the photocatalyst was assessed on P25, pure TiO2 and the best doped material. The photoactivity of these films, evaluated on the degradation of methylene blue under UV-A light, showed that the sample with the highest dopant concentration had an efficiency 4 times higher than pure TiO2 and 20 times higher than P25.

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“…Atitar et al have reported that Imazapyr shows 5 pKa corresponding to five different ionic equilibria [43]. The adsorption of Imazapyr on the surface of catalyst is accelerated with decreasing the pH of the solution, resulting in stronger and more stable electrostatic interactions, which is expected to enhance the photocatalytic degradation rate of Imazapyr [44]. Carrier et al have reported similar results for photocatalytic degradation of Imazapyr [45].…”

Section: Characterization Of Materialsmentioning

confidence: 91%

“…Compound (2), with m/z = 217 is formed in Pathway IV through decarboxylation of the pyrimidinic ring, confirming oxidation with holes h + , in addition to HO • , as we have recently shown for other compounds possessing carboxylic acid groups. The degradation mechanism involves competition between oxidative decarboxylation of chemisorbed compounds by semiconductor holes, and hydroxyl radical attack on physisorbed substrates [44]. The initial Imazapyr degradation products indicate that Imazapyr adsorbs on the surface of photocatalyst through the carboxylic group [45].…”

Section: Investigation Of the Reaction Products And Reaction Mechanismmentioning

confidence: 99%

Enhanced Photocatalytic Degradation of the Imidazolinone Herbicide Imazapyr upon UV/Vis Irradiation in the Presence of CaxMnOy-TiO2 Hetero-Nanostructures: Degradation Pathways and Reaction Intermediates

Bougarrani¹,

Sharma

Hamilton

et al. 2020

Nanomaterials

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The determination of reaction pathways and identification of products of pollutants degradation is central to photocatalytic environmental remediation. This work focuses on the photocatalytic degradation of the herbicide Imazapyr (2-(4-methyl-5-oxo-4-propan-2-yl-1H-imidazol-2-yl) pyridine-3-carboxylic acid) under UV-Vis and visible-only irradiation of aqueous suspensions of CaxMnOy-TiO2, and on the identification of the corresponding degradation pathways and reaction intermediates. CaxMnOy-TiO2 was formed by mixing CaxMnOy and TiO2 by mechanical grinding followed by annealing at 500 °C. A complete structural characterization of CaxMnOy-TiO2 was carried out. The photocatalytic activity of the hetero-nanostructures was determined using phenol and Imazapyr herbicide as model pollutants in a stirred tank reactor under UV-Vis and visible-only irradiation. Using equivalent loadings, CaxMnOy-TiO2 showed a higher rate (10.6 μM·h−1) as compared to unmodified TiO2 (7.4 μM·h−1) for Imazapyr degradation under UV-Vis irradiation. The mineralization rate was 4.07 µM·h−1 for CaxMnOy-TiO2 and 1.21 μM·h−1 for TiO2. In the CaxMnOy-TiO2 system, the concentration of intermediate products reached a maximum at 180 min of irradiation that then decreased to a half in 120 min. For unmodified TiO2, the intermediates continuously increased with irradiation time with no decrease observed in their concentration. The enhanced efficiency of the CaxMnOy-TiO2 for the complete degradation of the Imazapyr and intermediates is attributed to an increased adsorption of polar species on the surface of CaxMnOy. Based on LC-MS, photocatalytic degradation pathways for Imazapyr under UV-Vis irradiation have been proposed. Some photocatalytic degradation was obtained under visible-only irradiation for CaxMnOy-TiO2. Hydroxyl radicals were found to be main reactive oxygen species responsible for the photocatalytic degradation through radical scavenger investigations.

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Titanium Dioxide Nanoparticle Photocatalysed Degradation of Ibuprofen and Naproxen in Water: Competing Hydroxyl Radical Attack and Oxidative Decarboxylation by Semiconductor Holes

Cited by 33 publications

References 92 publications

Improved Photocatalyzed Degradation of Phenol, as a Model Pollutant, over Metal-Impregnated Nanosized TiO2

Improved Photocatalyzed Degradation of Phenol, as a Model Pollutant, over Metal-Impregnated Nanosized TiO2

Ambient temperature ZrO2-doped TiO2 crystalline photocatalysts: Highly efficient powders and films for water depollution

Enhanced Photocatalytic Degradation of the Imidazolinone Herbicide Imazapyr upon UV/Vis Irradiation in the Presence of CaxMnOy-TiO2 Hetero-Nanostructures: Degradation Pathways and Reaction Intermediates

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