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12 pages, 2099 KiB

Open AccessArticle

Wavelength Dependence of the Photocatalytic Performance of Pure and Doped TiO₂ Photocatalysts—A Reflection on the Importance of UV Excitability

by Gábor Veréb, Tamás Gyulavári, Orsolya Virág, Tünde Alapi, Klara Hernadi and Zsolt Pap

Catalysts 2022, 12(12), 1492; https://doi.org/10.3390/catal12121492 - 22 Nov 2022

Cited by 3 | Viewed by 2130

Abstract

The photocatalytic performances of doped and non-doped TiO₂ photocatalysts (TiO₂-s) were compared under solar and various types of artificial irradiation using phenol as a model contaminant. Non-doped (mainly anatase phase) TiO₂-s had significantly higher photocatalytic efficiency than highly [...] Read more.

The photocatalytic performances of doped and non-doped TiO₂ photocatalysts (TiO₂-s) were compared under solar and various types of artificial irradiation using phenol as a model contaminant. Non-doped (mainly anatase phase) TiO₂-s had significantly higher photocatalytic efficiency than highly visible-light-active TiO₂-s under natural solar irradiation. To explain these unexpected results, we measured the wavelength dependence of photocatalytic efficiency at six different wavelength ranges (λ = 300–650 nm). For this purpose, UV fluorescence tubes and five LED lights of different colors (violet, blue, green, yellow, and red) were used to activate the photocatalysts. The photon fluxes of the irradiation were measured, and apparent quantum yields were calculated for all irradiation conditions. The highest apparent quantum yield was 1.43% for our own TiO₂ (prepared via flame hydrolysis) under UV irradiation. However, apparent quantum yields were significantly lower (by 1–2 orders of magnitude) in the visible range, even for the most visible-light-active TiO₂. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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13 pages, 3710 KiB

Open AccessArticle

Thermal Stability and Utilization of 1D-Nanostructured Co₃O₄ Rods Derived by Simple Solvothermal Processing

by Vilko Mandić, Stanislav Kurajica, Milivoj Plodinec and Ivana Panžić

Catalysts 2022, 12(10), 1162; https://doi.org/10.3390/catal12101162 - 2 Oct 2022

Cited by 1 | Viewed by 1631

Abstract

For p-type semiconductor nanoparticles, such as the cobalt oxide spinel, enhancing the nanoparticle geometry can expose more of the surface and bring up the sensitivity and applicability, pointing to even more advantageous behaviour in comparison to n-type semiconductors which are known for a [...] Read more.

For p-type semiconductor nanoparticles, such as the cobalt oxide spinel, enhancing the nanoparticle geometry can expose more of the surface and bring up the sensitivity and applicability, pointing to even more advantageous behaviour in comparison to n-type semiconductors which are known for a somewhat faster reactivity. Here, we present a strategy that relies on fostering a simple synthetic route that can deliver reasonably or comparably performing p-type-semiconducting partially 1D-Co₃O₄ material prepared under less technically and economically demanding conditions. Structurally monophasic Co₃O₄ nanoparticles with a spinel structure were indicated by powder X-ray diffraction, while the presence of traces of organic-phase residuals in otherwise chemically homogeneous material was observed by Fourier-transform infrared spectroscopy. Scanning electron microscopy further showed that the observed fine nanoparticle matter formed agglomerates with the possible presence of rod-like formations. Interestingly, using transmission electron microscopy, it was possible to reveal that the agglomerates of the fine nanoparticulated material were actually nanostructured, i.e., the presence of 1D-shaped Co₃O₄ rods embedded in fine nanoparticulated matrix was confirmed. In conjunction with the N₂ adsorption–desorption isotherms, discussion about the orientation, exposure of nanostructured rod domains, and derivative geometry parameters was possible. The nanostructured Co₃O₄ material was shown to be stable up to 800 °C whereat the decomposition to CoO takes place. The specific surface area of the nanostructured sample was raised. For the purpose of testing the photoactivity of the prepared samples, simple sorption/photodegradation tests using methylene blue as the model pollutant were performed. The degradation performance of the prepared nanostructured Co₃O₄ was better described by a pseudo-second-order fit, suggesting that the prepared material is worth further development toward improved and stable immobilized photocatalysts. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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16 pages, 3434 KiB

Open AccessArticle

Sorbent and Photocatalytic Potentials of Local Clays for the Removal of Organic Xenobiotic: Case of Crystal Violet

by Sadou Dalhatou, Mouhamadou Sali, Samuel Tetteh, Abdoulaye Boubakari, Bouba Talami, Hicham Zeghioud, Abdoulaye Kane, Atef El Jery, Aymen Amin Assadi and David Olubiyi Obada

Catalysts 2022, 12(8), 899; https://doi.org/10.3390/catal12080899 - 16 Aug 2022

Cited by 4 | Viewed by 1887

Abstract

Natural materials are widely used in the field of environmental remediation and are appreciated for their surface physical and chemical properties. Clay constitutes a typical example. In this work, we report the evaluation of sorbent and photocatalytic potentials of local clay of two [...] Read more.

Natural materials are widely used in the field of environmental remediation and are appreciated for their surface physical and chemical properties. Clay constitutes a typical example. In this work, we report the evaluation of sorbent and photocatalytic potentials of local clay of two irrigated rice field waters in the degradation of crystal violet. The structural, textural and compositional properties of the local clay were investigated by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) analysis. The analysis results showed that these materials were composed mainly of quartz and kaolinite. The efficiency of these adsorbents (Y. Clay and L. Clay) to eliminate crystal violet dye from aqueous medium was examined at different initial concentrations, pH, contact time, adsorbent dose and the possible interference of inorganic salts from fertilizers. Kinetic studies showed that the adsorption process was well described by the pseudo-second order model and the equilibrium modelling results fitted adequately to the Freundlich model. The maximum amount of uptake capacity achieved at pH 2.0 was 18.40 (mg·g⁻¹) and 20.40 (mg·g⁻¹), respectively, for Y. Clay and L. Clay. The evaluation of the photocatalytic potential showed that the raw clay samples do not show photocatalytic activities during the 30 min of exposure to UV light. On the other hand, their photocatalytic potential is manifested when loaded with titanium dioxide (TiO₂). Clays coupled with TiO₂ under UV light showed an improvement in the degradation of the crystal violet dye by 15%. The synergistic effects between the high photocatalytic activity of TiO₂ and the strong adsorption capacity of clays can be one promising technique for in situ remediation of contaminated soaked rice field. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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11 pages, 2277 KiB

Open AccessArticle

NO_x Photooxidation over Different Noble Metals Modified TiO₂

by Kinga Skalska, Anna Malankowska, Jacek Balcerzak, Maria Gazda, Grzegorz Nowaczyk, Stefan Jurga and Adriana Zaleska-Medynska

Catalysts 2022, 12(8), 857; https://doi.org/10.3390/catal12080857 - 3 Aug 2022

Cited by 5 | Viewed by 1946

Abstract

We compared the activity enhancement effect of noble metal deposited on TiO₂ in photocatalytic nitrogen oxides oxidation. Titanium dioxide was decorated with Ag, Au, Pt or Pd in the sol-gel process. Synthesized catalysts were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller measurement (BET), [...] Read more.

We compared the activity enhancement effect of noble metal deposited on TiO₂ in photocatalytic nitrogen oxides oxidation. Titanium dioxide was decorated with Ag, Au, Pt or Pd in the sol-gel process. Synthesized catalysts were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller measurement (BET), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). All catalysts together with pure TiO₂ obtained by sol-gel (SG) technique were tested for their photocatalytic activity towards nitrogen oxide oxidation (high concentrations of 50, 150 and 250 ppm). FTIR spectrometry was used to determine the gas phase composition and identify TiO₂ surface species. The Ag0.1 sample turned out to be deactivated within 60 min of UV/Vis irradiation. Photocatalytic oxidation rate towards NO₂ turned to be the highest over SG (photocatalyst without metal deposition). NO₂ formation was also observed for Au0.1, Au0.5, Pt0.1, Pt0.5 and Pd0.1. The best NO_x removal, i.e., conversion to final product HNO₃ was obtained with the Au0.5 photocatalyst. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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14 pages, 3488 KiB

Open AccessArticle

Fabrication of WS₂/WSe₂ Z-Scheme Nano-Heterostructure for Efficient Photocatalytic Hydrogen Production and Removal of Congo Red under Visible Light

by Tsung-Mo Tien, Yu-Jen Chung, Chen-Tang Huang and Edward L. Chen

Catalysts 2022, 12(8), 852; https://doi.org/10.3390/catal12080852 - 3 Aug 2022

Cited by 16 | Viewed by 2706

Abstract

In this study, a novel tungsten disulfide/tungsten diselenide (WS₂/WSe₂) heterojunction photocatalyst by a facile hydrothermal process with great capable photocatalytic efficiency for hydrogen evolution from water and organic compound removal was discussed. The WS₂/WSe₂ heterojunction photocatalyst [...] Read more.

In this study, a novel tungsten disulfide/tungsten diselenide (WS₂/WSe₂) heterojunction photocatalyst by a facile hydrothermal process with great capable photocatalytic efficiency for hydrogen evolution from water and organic compound removal was discussed. The WS₂/WSe₂ heterojunction photocatalyst to form heterojunctions to inhibit the quick recombination rate of photo-response holes and electrons is reflected to be a useful method to enhance the capability of photocatalysis hydrogen production. The hydrogen production rate of the WS₂/WSe₂ photocatalyst approach is 3856.7 μmol/g/h, which is 12 and 11 folds the efficiency of bare WS₂ and WSe₂, respectively. Moreover, the excellent photocatalytic performance for Congo Red (CR) removal (92.4%) was 2.4 and 2.1 times higher than those of bare WS₂ and WSe₂, respectively. The great photocatalytic efficiency was owing to the capable electrons and holes separation of WS₂/WSe₂ and the construction of Z-scheme heterostructure, which possessed vigorous photocatalytic oxidation and reduction potentials. The novel one-dimensional structure of WS₂/WSe₂ heterojunction shortens the transport pathway of photo-induced electrons and holes. This work provided an insight to the pathway of interfacial separation and transferring for induced charge carriers, which can refer to the interfacial engineering of developed nanocomposite photocatalysts. It possessed great capable photocatalytic efficiency of hydrogen production and organic dye removal. This study offers an insight to the route of interfacial migration and separation for induced charge carriers to generating clean hydrogen energy and solve environmental pollution issue. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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11 pages, 4134 KiB

Open AccessArticle

The Organic Bromide Sources Adjusting the Shape and Band Structures of BiOBr Nanosheets for Enhanced Photodegradation Performances of BPA

by Donghao Xia, Kaiyang Sun, Youwei Zeng, Lulu Wang, Yi Zhang, Jie Shen, Zhaohui Wu and Wenhui Feng

Catalysts 2022, 12(8), 820; https://doi.org/10.3390/catal12080820 - 26 Jul 2022

Cited by 2 | Viewed by 1839

Abstract

Bismuth oxybromide (BiOBr) nanosheets were prepared by employing organic bromide sources. In the presence of organic bromide sources, the effects of different conditions on the band structure, shape, size, and light responses of BiOBr nanosheets were examined. The reaction conditions, including different types [...] Read more.

Bismuth oxybromide (BiOBr) nanosheets were prepared by employing organic bromide sources. In the presence of organic bromide sources, the effects of different conditions on the band structure, shape, size, and light responses of BiOBr nanosheets were examined. The reaction conditions, including different types of organic bromide sources, solvent, concentration, temperature, and time, were examined regarding the formation of BiOBr nanosheets. Then, the photocatalytic performances of different BiOBr nanosheets were also examined. Especially, the BiOBr nanosheets obtained from the addition of over 2 mmol of tetramethyl ammonium bromide (TMAB) in mannitol or EG at a higher temperature and longer reaction time showed superior photocatalytic activity. The enhanced photocatalytic performance of bisphenol A over these BiOBr nanosheets was achieved within 50 min due to efficient charge transfer and separation. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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22 pages, 4070 KiB

Open AccessArticle

Phyco-Synthesized Zinc Oxide Nanoparticles Using Marine Macroalgae, Ulva fasciata Delile, Characterization, Antibacterial Activity, Photocatalysis, and Tanning Wastewater Treatment

by Amr Fouda, Ahmed M. Eid, Ayman Abdelkareem, Hanan A. Said, Ehab F. El-Belely, Dalal Hussien M. Alkhalifah, Khalid S. Alshallash and Saad El-Din Hassan

Catalysts 2022, 12(7), 756; https://doi.org/10.3390/catal12070756 - 8 Jul 2022

Cited by 48 | Viewed by 3847

Abstract

The aqueous extract of marine green macroalgae, Ulva fasciata Delile, was harnessed for the synthesis of zinc oxide nanoparticles (ZnO-NPs). The conversion to ZnO-NPs was characterized by color change, UV–vis spectroscopy, FT-IR, TEM, SEM-EDX, and XRD. Data showed the formation of spherical and [...] Read more.

The aqueous extract of marine green macroalgae, Ulva fasciata Delile, was harnessed for the synthesis of zinc oxide nanoparticles (ZnO-NPs). The conversion to ZnO-NPs was characterized by color change, UV–vis spectroscopy, FT-IR, TEM, SEM-EDX, and XRD. Data showed the formation of spherical and crystalline ZnO-NPs with a size range of 3–33 nm. SEM-EDX revealed the presence of Zn and O in weight percentages of 45.3 and 31.62%, respectively. The phyco-synthesized ZnO-NPs exhibited an effective antibacterial activity against the pathogenic Gram-positive and Gram-negative bacteria. The bacterial clear zones ranged from 21.7 ± 0.6 to 14.7 ± 0.6 mm with MIC values of 50–6.25 µg mL⁻¹. The catalytic activity of our product was investigated in dark and visible light conditions, using the methylene blue (MB) dye. The maximum dye removal (84.9 ± 1.2%) was achieved after 140 min in the presence of 1.0 mg mL⁻¹ of our nanocatalyst under the visible light at a pH of 7 and a temperature of 35 °C. This percentage was decreased to 53.4 ± 0.7% under the dark conditions. This nanocatalyst showed a high reusability with a decreasing percentage of ~5.2% after six successive cycles. Under the optimum conditions, ZnO-NPs showed a high efficacy in decolorizing the tanning wastewater with a percentage of 96.1 ± 1.7%. Moreover, the parameters of the COD, BOD, TSS, and conductivity were decreased with percentages of 88.8, 88.5, 96.9, and 91.5%, respectively. Moreover, nano-ZnO had a high efficacy in decreasing the content of the tanning wastewater Cr (VI) from 864.3 ± 5.8 to 57.3 ± 4.1 mg L⁻¹ with a removal percentage of 93.4%. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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23 pages, 6105 KiB

Open AccessArticle

Synergistic Mechanism of Photocatalysis and Photo-Fenton by Manganese Ferrite and Graphene Nanocomposite Supported on Wood Ash with Real Sunlight Irradiation

by Maria Eliana Camargo Ferreira, Lara de Souza Soletti, Eduarda Gameleira Bernardino, Heloise Beatriz Quesada, Francielli Gasparotto, Rosângela Bergamasco and Natália Ueda Yamaguchi

Catalysts 2022, 12(7), 745; https://doi.org/10.3390/catal12070745 - 7 Jul 2022

Cited by 11 | Viewed by 2638

Abstract

The present research aimed to evaluate the photocatalytic activity of reduced graphene oxide and manganese ferrite nanocomposite supported on eucalyptus wood ash waste (WA) from industrial boilers, for the decolorization of methylene blue (MB) solutions, using sunlight as an irradiation source. For this, [...] Read more.

The present research aimed to evaluate the photocatalytic activity of reduced graphene oxide and manganese ferrite nanocomposite supported on eucalyptus wood ash waste (WA) from industrial boilers, for the decolorization of methylene blue (MB) solutions, using sunlight as an irradiation source. For this, the photocatalyst named MnFe₂O₄-G@WA was synthesized by a solvothermal method and characterized by analyzes of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, Brunauer–Emmett–Teller and zeta potential. Firstly, the photocatalyst was evaluated for photocatalytic decolorization of MB under different reaction conditions. Then, the influence of pH, photocatalyst dose and H₂O₂ was evaluated. MnFe₂O₄-G@WA showed 94% of efficiency for photocatalytic decolorization of MB under operating conditions of solar irradiation, 0.25 g/L of catalyst, 300 mg/L of H₂O₂. The proposed degradation reaction mechanism suggested that the photodegradation of MB was through a synergistic mechanism of photocatalysis and photo-Fenton reactions, with the combined action of the three materials used. The data adjusted to the first order kinetics from the Langmuir–Hinshelwood model. In addition, MnFe₂O₄-G@WA showed high stability, maintaining its efficiency above 90% after 5 cycles. The results indicated that the nanophotocatalyst is a potential technology for the decolorization of MB solutions. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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21 pages, 6374 KiB

Open AccessFeature PaperArticle

High-Performance Hydrogel Based on Modified Chitosan for Removal of Heavy Metal Ions in Borehole: A Case Study from the Bahariya Oasis, Egypt

by Mohammed F. Hamza, Saad H. Alotaibi, Yuezhou Wei and Noha M. Mashaal

Catalysts 2022, 12(7), 721; https://doi.org/10.3390/catal12070721 - 30 Jun 2022

Cited by 15 | Viewed by 2502

Abstract

Globally, there is a rising demand for water purification. This demand is driven by numerous factors, including economic growth, increasing population, water shortage, and deterioration of water quality. The current work highlights the manufacturing of environmentally friendly and highly efficient sorbent based on [...] Read more.

Globally, there is a rising demand for water purification. This demand is driven by numerous factors, including economic growth, increasing population, water shortage, and deterioration of water quality. The current work highlights the manufacturing of environmentally friendly and highly efficient sorbent based on chitosan nanoparticles after successive crosslinking (using glutaraldehyde) and modification through grafting of 4-aminoazobenzene-3,4′-disulfonic acid (AZDS) as a source of sulfonic groups. First, the produced sorbent was thoroughly specified using FTIR, TGA, SEM, SEM-EDX, pH_pzc, BET (nitrogen sorption desorption isotherms), and elemental analyses (EA). The sorbent was tested for the sorption of Fe(III) before application to highly contaminated iron water well samples. Next, the sorption was improved as the sulfonation process was conducted under the selected experimental conditions within 25 and 20 min with a maximum capacity of 2.7 and 3.0 mmol Fe g⁻¹ in visible light and under UV, respectively. Then, the uptake kinetics for both techniques were fitted by the pseudo-first-order rate equation (PFORE), in which the effect of the resistance to intraparticle diffusion has remained an unneglected factor, while the Langmuir equation has fitted the sorption isotherms. After that, the efficient desorption was achieved by using 0.2 M hydrochloric acid solution, and the desorption process was as fast as the sorption process; 15 min was sufficient for complete desorption. The sorbent shows high selectivity for heavy metal ions compared to the representative elements. Finally, the sorbent was used for the removal of heavy metal ions from a highly contaminated water well in the Bahariya Oasis and appeared to be highly efficient for heavy metal removal even in a diluted solution. Accordingly, it can be implemented in the task of water treatment. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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15 pages, 4161 KiB

Open AccessArticle

Palladium and Graphene Oxide Doped ZnO for Aqueous Acetamiprid Degradation under Visible Light

by Carolina Sayury Miyashiro and Safia Hamoudi

Catalysts 2022, 12(7), 709; https://doi.org/10.3390/catal12070709 - 28 Jun 2022

Cited by 7 | Viewed by 2232

Abstract

Acetamiprid is a neonicotinoid insecticide widely used in pest control. In recent years, it has been considered as a contaminant in groundwater, lakes, and rivers. Photocatalysis under visible light radiation proved to be an effective process for getting rid of several organic pollutants. [...] Read more.

Acetamiprid is a neonicotinoid insecticide widely used in pest control. In recent years, it has been considered as a contaminant in groundwater, lakes, and rivers. Photocatalysis under visible light radiation proved to be an effective process for getting rid of several organic pollutants. In the present work, photodegradation of aqueous acetamiprid was investigated over bare zinc oxide (ZnO) photocatalyst as well as ZnO doped with either palladium or palladium combined with graphene oxide. Both ZnO and doped-ZnO were synthesized via a microwave-assisted hydrothermal procedure. The obtained photocatalysts were characterized using different techniques. After 5 h of reaction at ambient temperature under visible light irradiation, acetamiprid conversions attained ca. 38, 82, and 98% in the presence of bare ZnO, Pd-doped ZnO and Pd-GO-doped ZnO photocatalysts, respectively, thus demonstrating the positive effect of Pd- and GO-doping on the photocatalytic activity of ZnO. In addition, Pd-GO-doped ZnO was shown to keep its activity even when it is recycled five times, thus proving its stability in the reaction medium. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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19 pages, 5047 KiB

Open AccessArticle

Synthesis of a Novel Adsorbent Based on Chitosan Magnetite Nanoparticles for the High Sorption of Cr (VI) Ions: A Study of Photocatalysis and Recovery on Tannery Effluents

by Maram H. Zahra, Mohammed F. Hamza, Gehan El-Habibi, Adel A.-H. Abdel-Rahman, Hamed I. Mira, Yuezhou Wei, Saad H. Alotaibi, Hamada H. Amer, Adel E.-S. Goda and Nora A. Hamad

Catalysts 2022, 12(7), 678; https://doi.org/10.3390/catal12070678 - 21 Jun 2022

Cited by 26 | Viewed by 2724

Abstract

This study aims to evaluate the functionalization of chitosan biopolymer with heterocyclic moieties of 2-thioxodihydropyrimidine-4,6(1H,5H)-dione used for enhancing the sorption of Cr ions from aqueous solution. A synthesized sorbent is a nanoscale particle (around 5–7 nm), which explains the fast kinetics of sorption. [...] Read more.

This study aims to evaluate the functionalization of chitosan biopolymer with heterocyclic moieties of 2-thioxodihydropyrimidine-4,6(1H,5H)-dione used for enhancing the sorption of Cr ions from aqueous solution. A synthesized sorbent is a nanoscale particle (around 5–7 nm), which explains the fast kinetics of sorption. The sorbent is specified using elemental analysis (EA), FTIR, BET (nitrogen sorption desorption isotherms), TGA, and SEM-EDX analyses. Sorption properties are investigated using ultraviolet emission (UV) but also using visible light (L). In the sorption diagram, the high sorption uptake and fast kinetics observed using ultraviolet conditions are shown. This work is conducted by removing Cr ions from highly contaminated tannery effluents, which have a high concentration of Cr associated with other poisonous elements such as Cd(II) and Pb(II). Under the selected conditions, complete sorption is performed during the first 60 and 45 min with a capacity of 2.05 and 2.5 mmol Cr g⁻¹ for the crosslinked chitosan (without functionalization) in L and UV, respectively. This sorption is enhanced by functionalizing to 5.7 and 6.8 mmol Cr g⁻¹ at the L and UV, respectively, as well as improving the sorption kinetics to 35 and 30 min for both techniques, respectively. The PFORE, and (Langmuir and Sips equations) fit the kinetics and isotherms, respectively. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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19 pages, 4199 KiB

Open AccessFeature PaperArticle

Aspergillus flavus-Mediated Green Synthesis of Silver Nanoparticles and Evaluation of Their Antibacterial, Anti-Candida, Acaricides, and Photocatalytic Activities

by Amr Fouda, Mohamed A. Awad, Zarraq E. AL-Faifi, Mohammed E. Gad, Areej A. Al-Khalaf, Reham Yahya and Mohammed F. Hamza

Catalysts 2022, 12(5), 462; https://doi.org/10.3390/catal12050462 - 21 Apr 2022

Cited by 50 | Viewed by 3748

Abstract

Aspergillus flavus F5 was used to reduce AgNO₃ to form silver nanoparticles (Ag-NPs) that were monitored by a color change from colorless to yellowish-brown. The characterizations were achieved by UV-Vis spectroscopy, FT-IR, TEM, SEM-EDX, and XRD. Data showed that there was a [...] Read more.

Aspergillus flavus F5 was used to reduce AgNO₃ to form silver nanoparticles (Ag-NPs) that were monitored by a color change from colorless to yellowish-brown. The characterizations were achieved by UV-Vis spectroscopy, FT-IR, TEM, SEM-EDX, and XRD. Data showed that there was a successful formation of crystalline, spherical shape Ag-NPs with a particle average size of 12.5 ± 5.1 nm. The FT-IR clarified the role of various functional groups in the reducing/capping process. EDX-SEM revealed that the main component of the as-formed sample was set to be mainly Ag with a weight percentage of 46.1%. The synthesized Ag-NPs exhibit antibacterial and anti-Candida activity against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, Candida albicans, C. glabrata, C. tropicalis, and C. parapsilosis, with inhibition zones ranging between 9.3 ± 0.5 to 20.8 ± 0.3 nm based on concentrations used and MIC values between 6.25 to 25 ppm. The mortality percentages of Tyrophagus putrescentiae mite species due to the mixing of their diet with different Ag-NPs concentrations of 0.5, 1.0, and 1.5 mg were 55.7 ± 2.1, 73.3 ± 1.5, and 87.4 ± 1.6% respectively after 20 days post-treatment. The catalytic activity of Ag-NPs to degrade methylene blue (MB) was investigated in the presence and absence of light irradiation. Data showed that a high photocatalytic degradation of MB compared with dark conditions at various times and concentrations. At a concentration of 70 mg/30 mL after 200 min., the dye removal percentages were 86.4 ± 0.4% in the presence of light irradiation versus 66.5 ± 1.1% in dark conditions. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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22 pages, 5789 KiB

Open AccessFeature PaperArticle

Photocatalytic Efficacy of Heterocyclic Base Grafted Chitosan Magnetite Nanoparticles on Sorption of Pb(II); Application on Mining Effluent

by Mohammed F. Hamza, Adel E.-S. Goda, Shunyan Ning, Hamed I. Mira, Adel A.-H. Abdel-Rahman, Yuezhou Wei, Toyohisa Fujita, Hamada H. Amer, Saad H. Alotaibi and Amr Fouda

Catalysts 2022, 12(3), 330; https://doi.org/10.3390/catal12030330 - 14 Mar 2022

Cited by 12 | Viewed by 3177

Abstract

Development of bio-based sorbents (i.e., chitosan moieties) at nanoscale size for the removal of metal contaminants is the main target of this research. Grafting with thiazole heterocyclic derivative gives fast kinetics sorption, highly metal loading, and good recyclability for mining leaching solution. Different [...] Read more.

Development of bio-based sorbents (i.e., chitosan moieties) at nanoscale size for the removal of metal contaminants is the main target of this research. Grafting with thiazole heterocyclic derivative gives fast kinetics sorption, highly metal loading, and good recyclability for mining leaching solution. Different analyses tools including (thermogravimetric analysis (TGA), scanning electron microscope and energy dispersive spectroscopy (SEM-EDX), X-ray diffraction (XRD), Fourier transform infrared (FTIR), BET surface area (nitrogen sorption desorption), titration, and TEM (transmission electron microscopy)) were used to investigate the chemical and textural properties of the functionalized sorbent. The sorption was measured in normal visible light and under UV emission. The highest capacity was measured at pH 5, which reached 0.251 mmol Pb g⁻¹ in visible light compared with 0.346 mmol Pb g⁻¹ under UV for the pristine crosslinked chitosan (MCc). The sorption performances were improved by functionalization; (0.7814 and 1.014 mmol Pb g⁻¹) for the functionalized sorbent (MCa-ATA) under visible light and UV, respectively. PFORE (pseudo-first-order rate equation) and RIDE (resistance to intraparticle diffusion) fit kinetics, the Sips equation is the most fit profile for the sorption isotherms for the MCc in either light and UV processes, while PFORE and RIDE for kinetics under light and UV for MCa-ATA and Sips in light and Sips and Langmuir under the UV emission. Finally, the sorbent was investigated toward a raffinate solution from ore processing and shows promising extraction tools for the most interesting elements. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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Review

Jump to: Research

23 pages, 3250 KiB

Open AccessFeature PaperReview

A Review of the Single-Step Flame Synthesis of Defective and Heterostructured TiO₂ Nanoparticles for Photocatalytic Applications

by Sovann Khan, Jin-Sung Park and Tatsumi Ishihara

Catalysts 2023, 13(1), 196; https://doi.org/10.3390/catal13010196 - 13 Jan 2023

Cited by 11 | Viewed by 3152

Abstract

Titanium dioxide (TiO₂) is an excellent UV-photocatalytic material that is widely used in various applications, including clean energy production, environmental remediation, and chemical production. However, the use of TiO₂ is limited in the field of visible light photocatalysis due to [...] Read more.

Titanium dioxide (TiO₂) is an excellent UV-photocatalytic material that is widely used in various applications, including clean energy production, environmental remediation, and chemical production. However, the use of TiO₂ is limited in the field of visible light photocatalysis due to its large bandgap and fast recombination rate between electron and hole pairs, which generally results in a low photocatalytic reaction. Defect/bandgap engineering by doping and the introduction of heterojunctions has been successfully employed to improve the photocatalytic activities of TiO₂ over a wide wavelength. To apply the unconventional structured TiO₂ with high photocatalytic performance to industries, the development of efficient methods for large-scale production is of high importance. Flame synthesis is a very promising method for the rapid production of nanoparticles. In this article, we summarize the latest reports on the synthesis of defective and heterostructured TiO₂ using the single-step method of flame synthesis. Fundamental understandings of reactor configurations, synthesis conditions, precursor preparation and their physicochemical properties are intensively discussed. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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21 pages, 2874 KiB

Open AccessReview

Applications of Fluorescent Carbon Dots as Photocatalysts: A Review

by Ricardo M. S. Sendão, Joaquim C. G. Esteves da Silva and Luís Pinto da Silva

Catalysts 2023, 13(1), 179; https://doi.org/10.3390/catal13010179 - 12 Jan 2023

Cited by 24 | Viewed by 4069

Abstract

Carbon dots (CDs) have attracted considerable interest from the scientific community due to their exceptional properties, such as high photoluminescence, broadband absorption, low toxicity, water solubility and (photo)chemical stability. As a result, they have been applied in several fields, such as sensing, bioimaging, [...] Read more.

Carbon dots (CDs) have attracted considerable interest from the scientific community due to their exceptional properties, such as high photoluminescence, broadband absorption, low toxicity, water solubility and (photo)chemical stability. As a result, they have been applied in several fields, such as sensing, bioimaging, artificial lighting and catalysis. In particular, CDs may act as sole photocatalysts or as part of photocatalytic nanocomposites. This study aims to provide a comprehensive review on the use of CDs as sole photocatalysts in the areas of hydrogen production via water splitting, photodegradation of organic pollutants and photoreduction and metal removal from wastewaters. Furthermore, key limitations preventing a wider use of CDs as photocatalysts are pointed out. It is our hope that this review will serve as a basis on which researchers may find useful information to develop sustainable methodologies for the synthesis and use of photocatalytic CDs. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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31 pages, 1759 KiB

Open AccessReview

An Insight into Carbon Nanomaterial-Based Photocatalytic Water Splitting for Green Hydrogen Production

by Muhammad Asghar Rasool, Rabia Sattar, Ayesha Anum, Sami A. Al-Hussain, Sajjad Ahmad, Ali Irfan and Magdi E. A. Zaki

Catalysts 2023, 13(1), 66; https://doi.org/10.3390/catal13010066 - 29 Dec 2022

Cited by 19 | Viewed by 4357

Abstract

At present, the energy shortage and environmental pollution are the burning global issues. For centuries, fossil fuels have been used to meet worldwide energy demand. However, thousands of tons of greenhouse gases are released into the atmosphere when fossil fuels are burned, contributing [...] Read more.

At present, the energy shortage and environmental pollution are the burning global issues. For centuries, fossil fuels have been used to meet worldwide energy demand. However, thousands of tons of greenhouse gases are released into the atmosphere when fossil fuels are burned, contributing to global warming. Therefore, green energy must replace fossil fuels, and hydrogen is a prime choice. Photocatalytic water splitting (PWS) under solar irradiation could address energy and environmental problems. In the past decade, solar photocatalysts have been used to manufacture sustainable fuels. Scientists are working to synthesize a reliable, affordable, and light-efficient photocatalyst. Developing efficient photocatalysts for water redox reactions in suspension is a key to solar energy conversion. Semiconductor nanoparticles can be used as photocatalysts to accelerate redox reactions to generate chemical fuel or electricity. Carbon materials are substantial photocatalysts for total WS under solar irradiation due to their high activity, high stability, low cost, easy production, and structural diversity. Carbon-based materials such as graphene, graphene oxide, graphitic carbon nitride, fullerenes, carbon nanotubes, and carbon quantum dots can be used as semiconductors, photosensitizers, cocatalysts, and support materials. This review comprehensively explains how carbon-based composite materials function as photocatalytic semiconductors for hydrogen production, the water-splitting mechanism, and the chemistry of redox reactions. Also, how heteroatom doping, defects and surface functionalities, etc., can influence the efficiency of carbon photocatalysts in H₂ production. The challenges faced in the PWS process and future prospects are briefly discussed. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis)

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