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13 pages, 4209 KiB

Open AccessArticle

Photodeposition of Silver on Zinc/Calcium Ferrite Nanoparticles: A Contribution to Efficient Effluent Remediation and Catalyst Reutilization

by Ricardo J. C. Fernandes, Carlos A. B. Magalhães, Ana Rita O. Rodrigues, Bernardo G. Almeida, Ana Pires, André Miguel Pereira, João Pedro Araujo, Elisabete M. S. Castanheira and Paulo J. G. Coutinho

Nanomaterials 2021, 11(4), 831; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11040831 - 24 Mar 2021

Cited by 2 | Viewed by 2016

Abstract

The efficient photodegradation of textile dyes is still a challenge, especially considering resistant azo dyes. In this work, zinc/calcium mixed ferrite nanoparticles prepared by the sol–gel method were coupled with silver by a photodeposition method to enhance the photocatalytic potency. The obtained zinc/calcium [...] Read more.

The efficient photodegradation of textile dyes is still a challenge, especially considering resistant azo dyes. In this work, zinc/calcium mixed ferrite nanoparticles prepared by the sol–gel method were coupled with silver by a photodeposition method to enhance the photocatalytic potency. The obtained zinc/calcium ferrites are mainly cubic-shaped nanoparticles sized 15 ± 2 nm determined from TEM and XRD and an optical bandgap of 1.6 eV. Magnetic measurements indicate a superparamagnetic behavior with saturation magnetizations of 44.22 emu/g and 27.97 emu/g, respectively, for Zn/Ca ferrite and Zn/Ca ferrite with photodeposited silver. The zinc/calcium ferrite nanoparticles with photodeposited silver showed efficient photodegradation of the textile azo dyes C.I. Reactive Blue 250 and C.I. Reactive Yellow 145. Subsequent cycles of the use of the photocatalyst indicate the possibility of magnetic recovery and reutilization without a significant loss of efficiency. Full article

(This article belongs to the Special Issue Application of Nanomaterials in Photocatalysis)

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17 pages, 4616 KiB

Open AccessArticle

Suitability of Different Titanium Dioxide Nanotube Morphologies for Photocatalytic Water Treatment

by Clayton Farrugia, Alessandro Di Mauro, Frederick Lia, Edwin Zammit, Alex Rizzo, Vittorio Privitera, Giuliana Impellizzeri, Maria Antonietta Buccheri, Giancarlo Rappazzo, Maurice Grech, Paul Refalo and Stephen Abela

Nanomaterials 2021, 11(3), 708; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11030708 - 11 Mar 2021

Cited by 15 | Viewed by 2612

Abstract

Photocatalysis has long been touted as one of the most promising technologies for environmental remediation. The ability of photocatalysts to degrade a host of different pollutants, especially recalcitrant molecules, is certainly appealing. Titanium dioxide (TiO₂) has been used extensively for this [...] Read more.

Photocatalysis has long been touted as one of the most promising technologies for environmental remediation. The ability of photocatalysts to degrade a host of different pollutants, especially recalcitrant molecules, is certainly appealing. Titanium dioxide (TiO₂) has been used extensively for this purpose. Anodic oxidation allows for the synthesis of a highly ordered nanotubular structure with a high degree of tunability. In this study, a series of TiO₂ arrays were synthesised using different electrolytes and different potentials. Mixed anatase-rutile photocatalysts with excellent wettability were achieved with all the experimental iterations. Under UVA light, all the materials showed significant photoactivity towards different organic pollutants. The nanotubes synthesised in the ethylene glycol-based electrolyte exhibited the best performance, with near complete degradation of all the pollutants. The antibacterial activity of this same material was similarly high, with extremely low bacterial survival rates. Increasing the voltage resulted in wider and longer nanotubes, characteristics which increase the level of photocatalytic activity. The ease of synthesis coupled with the excellent activity makes this a viable material that can be used in flat-plate reactors and that is suitable for photocatalytic water treatment. Full article

(This article belongs to the Special Issue Application of Nanomaterials in Photocatalysis)

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11 pages, 3770 KiB

Open AccessArticle

TiO₂ Nanowires with Doped g-C₃N₄ Nanoparticles for Enhanced H₂ Production and Photodegradation of Pollutants

by Liushan Jiang, Fanshan Zeng, Rong Zhong, Yu Xie, Jianli Wang, Hao Ye, Yun Ling, Ruobin Guo, Jinsheng Zhao, Shiqian Li and Yuying Hu

Nanomaterials 2021, 11(1), 254; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11010254 - 19 Jan 2021

Cited by 5 | Viewed by 3357

Abstract

With the rapid consumption of fossil fuels, along with the ever-increasing environmental pollution, it is becoming a top priority to explore efficient photocatalysts for the production of renewable hydrogen and degradation of pollutants. Here, we fabricated a composite of g-C₃N₄ [...] Read more.

With the rapid consumption of fossil fuels, along with the ever-increasing environmental pollution, it is becoming a top priority to explore efficient photocatalysts for the production of renewable hydrogen and degradation of pollutants. Here, we fabricated a composite of g-C₃N₄/TiO₂ via an in situ growth method under the conditions of high-temperature calcination. In this method, TiO₂ nanowires with a large specific surface area could provide enough space for loading more g-C₃N₄ nanoparticles to obtain C₃N₄/TiO₂ composites. Of note, the g-C₃N₄/TiO₂ composite could effectively photocatalyze both the degradation of several pollutants and production of hydrogen, both of which are essential for environmental governance. Combining multiple characterizations and experiments, we found that the heterojunction constructed by the TiO₂ and g-C₃N₄ could increase the photocatalytic ability of materials by prompting the separation of photogenerated carriers. Furthermore, the photocatalytic mechanism of the g-C₃N₄/TiO₂ composite was also clarified in detail. Full article

(This article belongs to the Special Issue Application of Nanomaterials in Photocatalysis)

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26 pages, 7886 KiB

Open AccessArticle

Microwave-Assisted Synthesis of Chalcopyrite/Silver Phosphate Composites with Enhanced Degradation of Rhodamine B under Photo-Fenton Process

by Shun-An Chang, Po-Yu Wen, Tsunghsueh Wu and Yang-Wei Lin

Nanomaterials 2020, 10(11), 2300; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10112300 - 20 Nov 2020

Cited by 10 | Viewed by 2524

Abstract

A new composite by coupling chalcopyrite (CuFeS₂) with silver phosphate (Ag₃PO₄) (CuFeS₂/Ag₃PO₄) was proposed by using a cyclic microwave heating method. The prepared composites were characterized by scanning and transmission electron [...] Read more.

A new composite by coupling chalcopyrite (CuFeS₂) with silver phosphate (Ag₃PO₄) (CuFeS₂/Ag₃PO₄) was proposed by using a cyclic microwave heating method. The prepared composites were characterized by scanning and transmission electron microscopy and X-ray diffraction, Fourier-transform infrared, UV–Vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. Under optimum conditions and 2.5 W irradiation (wavelength length > 420 nm, power density = 0.38 Wcm⁻²), 96% of rhodamine B (RhB) was degraded by CuFeS₂/Ag₃PO₄ within a 1 min photo-Fenton reaction, better than the performance of Ag₃PO₄ (25% degradation within 10 min), CuFeS₂ (87.7% degradation within 1 min), and mechanically mixed CuFeS₂/Ag₃PO₄ catalyst. RhB degradation mainly depended on the amount of hydroxyl radicals generated from the Fenton reaction. The degradation mechanism of CuFeS₂/Ag₃PO₄ from the photo-Fenton reaction was deduced using a free radical trapping experiment, the chemical reaction of coumarin, and photocurrent and luminescence response. The incorporation of CuFeS₂ in Ag₃PO₄ enhanced the charge separation of Ag₃PO₄ and reduced Ag₃PO₄ photocorrosion as the photogenerated electrons on Ag₃PO₄ were transferred to regenerate Cu²⁺/Fe³⁺ ions produced from the Fenton reaction to Cu⁺/Fe²⁺ ions, thus simultaneously maintaining the CuFeS₂ intact. This demonstrates the synergistic effect on material stability. However, hydroxyl radicals were produced by both the photogenerated holes of Ag₃PO₄ and the Fenton reaction of CuFeS₂ as another synergistic effect in catalysis. Notably, the degradation performance and the reusability of CuFeS₂/Ag₃PO₄ were promoted. The practical applications of this new material were demonstrated from the effective performance of CuFeS₂/Ag₃PO₄ composites in degrading various dyestuffs (90–98.9% degradation within 10 min) and dyes in environmental water samples (tap water, river water, pond water, seawater, treated wastewater) through enhanced the Fenton reaction under sunlight irradiation. Full article

(This article belongs to the Special Issue Application of Nanomaterials in Photocatalysis)

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14 pages, 4339 KiB

Open AccessArticle

Study of the Photothermal Catalytic Mechanism of CO₂ Reduction to CH₄ by Ruthenium Nanoparticles Supported on Titanate Nanotubes

by Maria Novoa-Cid and Herme G. Baldovi

Nanomaterials 2020, 10(11), 2212; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10112212 - 06 Nov 2020

Cited by 11 | Viewed by 2666

Abstract

The Sabatier reaction could be a key tool for the future of the renewable energy field due to the potential of this reaction to produce either fuels or to stabilize H₂ in the form of stable chemicals. For this purpose, a new [...] Read more.

The Sabatier reaction could be a key tool for the future of the renewable energy field due to the potential of this reaction to produce either fuels or to stabilize H₂ in the form of stable chemicals. For this purpose, a new composite made of ruthenium oxide nanoparticles (NPs) deposited on titanate nanotubes (TiNTs) was tested. Titanate nanotubes are a robust semiconductor with a one-dimensional (1D) morphology that results in a high contact area making this material suitable for photocatalysis. Small ruthenium nanoparticles (1.5 nm) were deposited on TiNTs at different ratios by Na⁺-to-Ru³⁺ ion exchanges followed by calcination. These samples were tested varying light power and temperature conditions to study the reaction mechanism during catalysis. Methanation of CO₂ catalyzed by Ru/TiNT composite exhibit photonic and thermic contributions, and their ratios vary with temperature and light intensity. The synthesized composite achieved a production rate of 12.4 mmol CH₄·g_cat⁻¹·h⁻¹ equivalent to 110.7 mmol of CH₄·g_Ru⁻¹·h⁻¹ under 150 mW/cm² simulated sunlight irradiation at 210 °C. It was found that photo-response derives either from Ru nanoparticle excitation in the visible (VIS) and near-infrared (NIR) region (photothermal and plasmon excitation mechanism) or from TiNT excitation in the ultraviolet (UV) region leading to electron–hole separation and photoinduced electron transfer. Full article

(This article belongs to the Special Issue Application of Nanomaterials in Photocatalysis)

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27 pages, 4096 KiB

Open AccessArticle

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

by S. Belekbir, M. El Azzouzi, A. El Hamidi, L. Rodríguez-Lorenzo, J. Arturo Santaballa and M. Canle

Nanomaterials 2020, 10(5), 996; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10050996 - 22 May 2020

Cited by 24 | Viewed by 3324

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Application of Nanomaterials in Photocatalysis)

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22 pages, 8758 KiB

Open AccessArticle

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

by Salma Bougarrani, Preetam K. Sharma, Jeremy W. J. Hamilton, Anukriti Singh, Moisés Canle, Mohammed El Azzouzi and John Anthony Byrne

Nanomaterials 2020, 10(5), 896; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10050896 - 08 May 2020

Cited by 5 | Viewed by 3027

Abstract

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 Ca_x [...] Read more.

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 Ca_xMnO_y-TiO₂, and on the identification of the corresponding degradation pathways and reaction intermediates. Ca_xMnO_y-TiO₂ was formed by mixing Ca_xMnO_y and TiO₂ by mechanical grinding followed by annealing at 500 °C. A complete structural characterization of Ca_xMnO_y-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, Ca_xMnO_y-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 Ca_xMnO_y-TiO₂ and 1.21 μM·h⁻¹ for TiO₂. In the Ca_xMnO_y-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 Ca_xMnO_y-TiO₂ for the complete degradation of the Imazapyr and intermediates is attributed to an increased adsorption of polar species on the surface of Ca_xMnO_y. 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 Ca_xMnO_y-TiO₂. Hydroxyl radicals were found to be main reactive oxygen species responsible for the photocatalytic degradation through radical scavenger investigations. Full article

(This article belongs to the Special Issue Application of Nanomaterials in Photocatalysis)

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1 pages, 179 KiB

Open AccessErratum

Erratum: Canle, M., et al. Improved Photocatalyzed Degradation of Phenol, as a Model Pollutant, over Metal-Impregnated Nanosized TiO₂. Nanomaterials 2020, 10, 996

by S. Belekbir, M. El Azzouzi, A. El Hamidi, L. Rodríguez-Lorenzo, J. Arturo Santaballa and M. Canle

Nanomaterials 2020, 10(6), 1109; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10061109 - 03 Jun 2020

Cited by 1 | Viewed by 1484

Abstract

The authors wish to make the following corrections to this paper: [...] Full article

(This article belongs to the Special Issue Application of Nanomaterials in Photocatalysis)

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