Catalysts

Editorial

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5 pages, 172 KiB

Open AccessEditorial

Advanced Oxidation Catalysts—Innovative Approaches and Emerging Trends

by Meng Li and Chenxi Li

Catalysts 2024, 14(10), 700; https://doi.org/10.3390/catal14100700 - 8 Oct 2024

Viewed by 581

Abstract

Novel oxidation catalysts in water treatment and purification have garnered major attention due to the growing demand for clean water resources [...] Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

Research

Jump to: Editorial, Review

13 pages, 3012 KiB

Open AccessCommunication

Magnetically Separable Mixed-Phase α/γ-Fe₂O₃ Catalyst for Photo-Fenton-like Oxidation of Rhodamine B

by Asiyat Magomedova, Abdulgalim Isaev, Farid Orudzhev, Dinara Sobola, Rabadanov Murtazali, Alina Rabadanova, Nabi S. Shabanov, Mingshan Zhu, Ruslan Emirov, Sultanakhmed Gadzhimagomedov, Nariman Alikhanov and Kaviyarasu Kasinathan

Catalysts 2023, 13(5), 872; https://doi.org/10.3390/catal13050872 - 11 May 2023

Cited by 12 | Viewed by 2338

Abstract

Iron oxides are widely used as catalysts for photo-Fenton-like processes for dye oxidation. In this study, we report on the synthesis of an α/γ-Fe₂O₃ mixed-phase catalyst with magnetic properties for efficient separation. The catalyst was synthesized using glycine–nitrate precursors. The [...] Read more.

Iron oxides are widely used as catalysts for photo-Fenton-like processes for dye oxidation. In this study, we report on the synthesis of an α/γ-Fe₂O₃ mixed-phase catalyst with magnetic properties for efficient separation. The catalyst was synthesized using glycine–nitrate precursors. The synthesized α/γ-Fe₂O₃ samples were characterized using scanning electron microscopy, X-ray diffraction spectroscopy (XRD), Raman shift spectroscopy, X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometer (VSM). The diffraction peaks were indexed with two phases, α-Fe₂O₃ as the main phase (79.6 wt.%) and γ-Fe₂O₃ as the secondary phase (20.4 wt.%), determined using the Rietveld refinement method. The presence of Fe²⁺ was attributed to oxygen vacancies. The mixed-phase α/γ-Fe₂O₃ catalyst exhibited remarkable photo-Fenton-like degradation performance for Rhodamine B (RhB) in neutral pH. The effects of operating parameters, including H₂O₂ concentration, catalyst concentration, and RhB concentration, on the degradation efficiency were investigated. The removal rates of color were 99.2% after 12 min at optimal conditions of photo-Fenton-like oxidation of RhB. The sample exhibited a high saturation magnetization of 28.6 emu/g. Additionally, the α/γ-Fe₂O₃ mixed-phase catalyst showed long-term stability during recycle experiments, with only a 5% decrease in activity. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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13 pages, 2990 KiB

Open AccessArticle

Enhanced Visible-Light Photocatalytic Activities of CeVO₄-V₂O₃ Composite: Effect of Ethylene Glycol

by Yuxin Wang, Yinxiu Jin, Minghan Jia, Hu Ruan, Xuefen Tao, Xuefeng Liu, Guang Lu and Xiaodong Zhang

Catalysts 2023, 13(4), 659; https://doi.org/10.3390/catal13040659 - 27 Mar 2023

Cited by 6 | Viewed by 1721

Abstract

CeVO₄-V₂O₃ composites were prepared by simple hydrothermal method, and the effects of ethylene glycol(EG) on the products were studied by XRD, N₂ adsorption–desorption, SEM, EDS, XPS, PL and UV-vis spectra. The characterization reveals a slight decrease in [...] Read more.

CeVO₄-V₂O₃ composites were prepared by simple hydrothermal method, and the effects of ethylene glycol(EG) on the products were studied by XRD, N₂ adsorption–desorption, SEM, EDS, XPS, PL and UV-vis spectra. The characterization reveals a slight decrease in surface area and a slight enhancement of visible light absorption in the final sample, while the crystalline phase, morphology and separation efficiency of the collective carriers are severely affected by the EG. At the same time, the photocatalytic effect of CeVO₄-V₂O₃ composites was evaluated by the degradation rate of methylene blue (MB) under simulated visible light. The sample for 10 mL EG obtained the highest efficiency of 96.9%, while the one for 15 mL EG showed the lowest efficiency of 67.5% within 300 min. The trapping experiments and ESR experiment showed that the contribution of active species to the photocatalytic degradation of MB was ∙OH > h⁺ > ∙O²⁻ in descending order, and a possible degradation mechanism was proposed. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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16 pages, 2110 KiB

Open AccessArticle

Sonocatalytic Degradation of Chrysoidine R Dye Using Ultrasonically Synthesized NiFe₂O₄ Catalyst

by Yogesh M. Gote, Pankaj S. Sinhmar and Parag R. Gogate

Catalysts 2023, 13(3), 597; https://doi.org/10.3390/catal13030597 - 16 Mar 2023

Cited by 11 | Viewed by 1790

Abstract

The novel ultrasound-assisted co-precipitation method was successfully applied for the synthesis of the NiFe₂O₄ catalyst, which offered the advantages of lower particle size and better crystalline structure without affecting the phase planes. Furthermore, the efficacy of synthesized catalysts was evaluated [...] Read more.

The novel ultrasound-assisted co-precipitation method was successfully applied for the synthesis of the NiFe₂O₄ catalyst, which offered the advantages of lower particle size and better crystalline structure without affecting the phase planes. Furthermore, the efficacy of synthesized catalysts was evaluated using ultrasound-assisted catalytic degradation of Chrysoidine R dye. The study was designed to evaluate the effect of different parameters, such as pH, duty cycle, power output, and catalyst loading on Chrysoidine R dye degradation using a 5 wt% NiFe₂O₄ catalyst synthesized ultrasonically. At the optimized condition of 120 W ultrasonic power, 70% duty cycle, 3 pH, 0.5 g/L catalyst loading, and 160 min of reaction time, the best degradation of 45.01% was obtained. At similar conditions, the conventionally synthesized catalyst resulted in about 15% less degradation. Chrysoidine R dye degradation was observed to follow second-order kinetics. To accelerate the degradation, studies were performed using hydrogen peroxide at various loadings where it was elucidated that optimum use of 75 ppm loading showed the maximum degradation of 92.83%, signifying the important role of the co-oxidant in ultrasound-assisted catalytic degradation of Chrysoidine R dye. Overall, the present study clearly demonstrated the potential benefits of ultrasound in catalyst synthesis as well as in catalytic degradation. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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21 pages, 3002 KiB

Open AccessArticle

A Comparison of Different Reagents Applicable for Destroying Halogenated Anionic Textile Dye Mordant Blue 9 in Polluted Aqueous Streams

by Barbora Kamenická and Tomáš Weidlich

Catalysts 2023, 13(3), 460; https://doi.org/10.3390/catal13030460 - 22 Feb 2023

Cited by 4 | Viewed by 2072

Abstract

This article aimed to compare the degradation efficiencies of different reactants applicable for the oxidative or reductive degradation of a chlorinated anionic azo dye, Mordant Blue 9 (MB9). In this article, the broadly applied Fenton oxidation process was optimized for the oxidative treatment [...] Read more.

This article aimed to compare the degradation efficiencies of different reactants applicable for the oxidative or reductive degradation of a chlorinated anionic azo dye, Mordant Blue 9 (MB9). In this article, the broadly applied Fenton oxidation process was optimized for the oxidative treatment of MB9, and the obtained results were compared with other innovative chemical reduction methods. In the reductive degradation of MB9, we compared the efficiencies of different reductive agents such as Fe⁰ (ZVI), Al⁰, the Raney Al-Ni alloy, NaBH₄, NaBH₄/Na₂S₂O₅, and other combinations of these reductants. The reductive methods aimed to reduce the azo bond together with the bound chlorine in the structure of MB9. The dechlorination of MB9 produces non-chlorinated aminophenols, which are more easily biodegradable in wastewater treatment plants (WWTPs) compared to their corresponding chlorinated aromatic compounds. The efficiencies of both the oxidative and reductive degradation processes were monitored by visible spectroscopy and determined based on the chemical oxygen demand (COD). The hydrodechlorination of MB9 to non-chlorinated products was expressed using the measurement of adsorbable organically bound halogens (AOXs) and controlled by LC–MS analyses. Optimally, 28 mol of H₂SO₄, 120 mol of H₂O₂, and 4 mol of FeSO₄ should be applied per one mol of dissolved MB9 dye for a practically complete oxidative degradation after 20 h of action. On the other hand, the application of the Al-Ni alloy/NaOH (100 mol of Al in the Al-Ni alloy + 100 mol of NaOH per one mol of MB9) proceeded smoothly and seven-times faster than the Fenton reaction, consumed similar quantities of reagents, and produced dechlorinated aminophenols. The cost of the Al-Ni alloy/NaOH-based method could be decreased significantly by applying a pretreatment with Al⁰/NaOH and a subsequent hydrodechlorination using smaller Al-Ni alloy doses. The homogeneous reduction accompanied by HDC using in situ produced Na₂S₂O₄ (by the action of NaBH₄/Na₂S₂O₅) was an effective, rapid, and simple treatment method. This reductive system consumed quantities of reagents that are almost twice as low (66 mol of NaBH₄ + 66 mol of Na₂S₂O₅ + 18 mol of H₂SO₄ per one mol of MB9) in comparison with the other oxidative/reductive systems and allowed the effective and fast degradation of MB9 accompanied by the effective removal of AOX. A comparison of the oxidative and reductive methods for chlorinated acid azo dye MB9 degradation showed that an innovative combination of reduction methods offers a smooth, simple, and efficient degradation and hydrodehalogenation of chlorinated textile MB9 dye. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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13 pages, 5256 KiB

Open AccessFeature PaperArticle

Synthesis of Novel Zn₃V₂O₈/Ag Nanocomposite for Efficient Photocatalytic Hydrogen Production

by Fahad A. Alharthi, Alanood Sulaiman Ababtain, Hend Khalid Aldubeikl, Hamdah S. Alanazi and Imran Hasan

Catalysts 2023, 13(3), 455; https://doi.org/10.3390/catal13030455 - 21 Feb 2023

Cited by 3 | Viewed by 2018

Abstract

In this study, we fabricated Zn₃V₂O₈ and a Ag-modified Zn₃V₂O₈ composite (Zn₃V₂O₈/Ag) by utilizing effective and benign approaches. Further characterization techniques such as powder X-ray diffraction (XRD) [...] Read more.

In this study, we fabricated Zn₃V₂O₈ and a Ag-modified Zn₃V₂O₈ composite (Zn₃V₂O₈/Ag) by utilizing effective and benign approaches. Further characterization techniques such as powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) were explored to examine the phase and structural properties, respectively, of the synthesized Zn₃V₂O₈/Ag and Zn₃V₂O₈/Ag composite materials. The oxidation states and elemental composition of the synthesized Zn₃V₂O₈/Ag and Zn₃V₂O₈/Ag were characterized by adopting X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX). The optical band gaps of the synthesized Zn₃V₂O₈/Ag and Zn₃V₂O₈/Ag were examined by employing ultraviolet–visible (UV-vis) diffuse reflection spectroscopy. HRTEM images clearly show that ZnV@Ag NC has a hexagonal plate-like morphology. Subsequently, Zn₃V₂O₈ and Zn₃V₂O₈/Ag were used as photocatalysts for photocatalytic hydrogen (H₂) production. It was observed that after Ag doping, the energy band gap of ZnV was reduced from 2.33 eV to 2.19 eV. EDX mapping images also show the presence of Ag, O, Zn, and V elements and confirm the formation of ZnV@Ag NC with good phase purity. Observations clearly showed the presence of excellent photocatalytic properties of the synthesized photocatalyst. The Zn₃V₂O₈/Ag photocatalyst exhibited H₂ generation of 37.52 µmolg⁻¹h⁻¹, which is higher compared to pristine Zn₃V₂O₈. The Zn₃V₂O₈/Ag photocatalyst also demonstrated excellent reusability, including decent stability. The reusability experiments suggested that ZnV@Ag NC has excellent cyclic stability for up to six cycles. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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17 pages, 5580 KiB

Open AccessArticle

Hydrothermal Synthesis of Bimetallic (Zn, Co) Co-Doped Tungstate Nanocomposite with Direct Z-Scheme for Enhanced Photodegradation of Xylenol Orange

by Fahad A. Alharthi, Wedyan Saud Al-Nafaei, Alanoud Abdullah Alshayiqi, Hamdah S. Alanazi and Imran Hasan

Catalysts 2023, 13(2), 404; https://doi.org/10.3390/catal13020404 - 14 Feb 2023

Cited by 7 | Viewed by 2172

Abstract

In the present study, pristine ZnWO₄, CoWO_4, and mixed metal Zn_0.5Co_0.5WO₄ were synthesized through the hydrothermal process using a Teflon-lined autoclave at 180 ℃. The synthesized nanomaterials were characterized by various spectroscopic techniques, such as [...] Read more.

In the present study, pristine ZnWO₄, CoWO_4, and mixed metal Zn_0.5Co_0.5WO₄ were synthesized through the hydrothermal process using a Teflon-lined autoclave at 180 ℃. The synthesized nanomaterials were characterized by various spectroscopic techniques, such as TEM, FTIR, UV–vis, XRD, and SEM-EDX-mapping to confirm the formation of nanocomposite material. The synthesized materials were explored as photocatalysts for the degradation of xylenol orange (XO) under a visible light source and a comparative study was explored to check the efficiency of the bimetallic co-doped nanocomposite to the pristine metal tungstate NPs. XRD analysis proved that reinforcement of Co²⁺ in ZnWO₄ lattice results in a reduction in interplanar distance from 0.203 nm to 0.185 nm, which is reflected in its crystallite size, which reduced from 32 nm to 24 nm. Contraction in crystallite size reflects on the optical properties as the energy bandgap of ZnWO₄ reduced from 3.49 eV to 3.33 eV in Zn_0.5Co_0.5WO₄, which is due to the formation of a Z-scheme for charge transfer and enhancement in photocatalytic efficiency. The experimental results suggested that ZnWO₄, CoWO_4, and Zn_0.5Co_0.5WO₄ NPs achieved a photocatalytic efficiency of 97.89%, 98.10%, and 98.77% towards XO in 120 min of visible solar light irradiation. The kinetics of photodegradation was best explained by pseudo-first-order kinetics and the values of apparent rate const (k_app) also supported the enhanced photocatalytic efficiency of mixed metal Zn_0.5Co_0.5WO₄ NPs towards XO degradation. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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13 pages, 4841 KiB

Open AccessFeature PaperArticle

G-C₃N₄ Dots Decorated with Hetaerolite: Visible-Light Photocatalyst for Degradation of Organic Contaminants

by Zahra Lahootifar, Aziz Habibi-Yangjeh, Shima Rahim Pouran and Alireza Khataee

Catalysts 2023, 13(2), 346; https://doi.org/10.3390/catal13020346 - 3 Feb 2023

Cited by 5 | Viewed by 1854

Abstract

In this paper, a facile hydrothermal approach was used to integrate graphitic carbon nitride dots (CNDs) with hetaerolite (ZnMn₂O₄) at different weight percentages. The morphology, microstructure, texture, electronic, phase composition, and electrochemical properties were identified by field emission scanning [...] Read more.

In this paper, a facile hydrothermal approach was used to integrate graphitic carbon nitride dots (CNDs) with hetaerolite (ZnMn₂O₄) at different weight percentages. The morphology, microstructure, texture, electronic, phase composition, and electrochemical properties were identified by field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), ultraviolet-visible diffuse reflectance (UV-vis DR), photoluminescence (PL), electrochemical impedance spectroscopy (EIS), Brunauer–Emmett–Teller (BET), Barrett–Joyner–Halenda (BJH), and photocurrent density. The results of XRD, FT-IR, EDX, and XPS analyses confirmed the synthesis of CNDs/ZnMn₂O₄ (20%) nanocomposite. As per PL, EIS, and photocurrent outcomes, the binary CNDs/ZnMn₂O₄ nanocomposite revealed superior features for interfacial transferring of charge carriers. The developed p–n heterojunction at the interface of CNDs and ZnMn₂O₄ nanoparticles partaken a significant role in the impressive charge segregation and migration. The binary nanocomposites were employed for the photodegradation of several dye pollutants, including rhodamine B (RhB), fuchsin, malachite green (MG), and methylene blue (MB) at visible wavelengths. Amongst the fabricated photocatalysts, the CNDs/ZnMn₂O₄ (20%) nanocomposite gave rise to about 98% RhB degradation efficiency within 45 min with the rate constant of 747 × 10⁻⁴ min⁻¹, which was 66.5-, 3.44-, and 2.72-fold superior to the activities of CN, CNDs, and ZnMn₂O₄ photocatalysts, respectively. The impressive photodegradation performance of this nanocomposite was not only associated with the capacity for impressive visible-light absorption and boosted separation and transport of charge carriers, but also with its large surface area. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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18 pages, 3861 KiB

Open AccessArticle

Synthesis of Nanocrystalline Metal Tungstate NiWO₄/CoWO₄ Heterojunction for UV-Light-Assisted Degradation of Paracetamol

by Fahad Ahmed Alharthi, Alanoud Abdullah Alshayiqi, Wedyan Saud Al-Nafaei, Adel El Marghany, Hamdah Saleh Alanazi and Imran Hasan

Catalysts 2023, 13(1), 152; https://doi.org/10.3390/catal13010152 - 9 Jan 2023

Cited by 6 | Viewed by 2690

Abstract

The discharge of pharma products such as paracetamol (PCT) into water has resulted in great harm to humans and emerged as a potential threat requiring a solution. Therefore, the development of smart and efficient materials as photocatalysts has become imperative in order to [...] Read more.

The discharge of pharma products such as paracetamol (PCT) into water has resulted in great harm to humans and emerged as a potential threat requiring a solution. Therefore, the development of smart and efficient materials as photocatalysts has become imperative in order to treat PCT in wastewater. The present study demonstrates the synthesis of pristine NiWO₄ and CoWO₄ and a heterojunction nanostructure, NiWO₄/CoWO₄, through a hydrothermal process using a Teflon-lined autoclave at 180 °C for 18 h. Various spectroscopic techniques, such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), ultraviolet–visible (UV–Vis), transmission electron microscopy (TEM), scanning electron microscopy–energy dispersive X-ray (SEM–EDX), and X-ray photoelectron spectroscopy (XPS) were utilised to determine the lattice, structural, optical, and morphological information of the solid nanomaterial upon heterojunction formation. The synthesised nanomaterials were exploited for the photocatalytic degradation of paracetamol (PCT) under UV light irradiation. Photocatalytic experiments were performed for the optimization of various reaction parameters, such as irradiation time, pH, catalyst dose, and PCT concentration at room temperature. The results obtained suggested that the heterojunction nanocomposite NiWO₄/CoWO₄ exhibited enhanced photocatalytic efficiency (97.42%) with PCT as compared to its precursors—96.50% for NiWO₄ and 97.12% for CoWO₄. The photocatalytic data were best defined by the Langmuir–Hinshelwood (L–H) model of pseudo-first-order kinetics, with apparent rates constant at 0.015 min⁻¹ for NiWO₄, 0.017 min⁻¹ for CoWO₄, and 0.019 min⁻¹ for NiWO₄/CoWO₄ NC. It was observed that NiWO₄/CoWO₄ NC with enhanced optical properties effected a higher rate of PCT degradation due to the improved bandgap energy upon heterojunction formation. The scavenger test revealed the involvement of ^•OH radicals as reactive oxidant species (ROS) in PCT degradation. The material was found to be highly stable and reusable for the degradation of PCT at optimized reaction conditions. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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16 pages, 3470 KiB

Open AccessArticle

Removal of Persistent Acid Pharmaceuticals by a Biological-Photocatalytic Sequential Process: Clofibric Acid, Diclofenac, and Indomethacin

by María J. Cruz-Carrillo, Rosa M. Melgoza-Alemán, Cecilia Cuevas-Arteaga and José B. Proal-Nájera

Catalysts 2022, 12(11), 1488; https://doi.org/10.3390/catal12111488 - 21 Nov 2022

Viewed by 1399

Abstract

The removal of three acid pharmaceuticals—clofibric acid (CLA), diclofenac (DCL), and indomethacin (IND)—by a biological-photocatalytic sequential system was studied. These pharmaceutical active compounds (PhACs) are considered to persist in the environment and have been found in water and sewage, producing adverse effects on [...] Read more.

The removal of three acid pharmaceuticals—clofibric acid (CLA), diclofenac (DCL), and indomethacin (IND)—by a biological-photocatalytic sequential system was studied. These pharmaceutical active compounds (PhACs) are considered to persist in the environment and have been found in water and sewage, producing adverse effects on the aquatic environment. For the biological process, in batch experiments, a fixed bed bioreactor and activated sludge (hybrid bioreactor), under aerobic conditions, was used as pretreatment. The pretreated effluent was exposed to a photocatalytic process employing TiO₂ nanotubular films (NTF-TiO₂) with the following characteristics: an internal diameter of 112 nm, a wall thickness of 26 nm, nanotube length of 15 µm, a roughness factor of 1840 points, and an anatase-rutile crystalline structure. In the hybrid bioreactor, 39% IND and 50% ACL and DCL were removed. The biological-photocatalysis sequential system achieved the degradation of up to 90% of the initial concentrations of the three acid pharmaceuticals studied. This approach appears to be a viable alternative for the treatment of these non-biodegradable effluents. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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14 pages, 1937 KiB

Open AccessArticle

Effect of the Active Metal on the NO_x Formation during Catalytic Combustion of Ammonia SOFC Off-Gas

by Tobias Weissenberger, Ralf Zapf, Helmut Pennemann and Gunther Kolb

Catalysts 2022, 12(10), 1186; https://doi.org/10.3390/catal12101186 - 7 Oct 2022

Cited by 7 | Viewed by 2284

Abstract

Catalytic combustion of hydrogen and ammonia containing off-gas surrogate from an ammonia solid oxide fuel cell (SOFC) was studied with a focus on nitrogen oxides (NO_x) mitigation. Noble and transition metals (Pt, Pd, Ir, Ru, Rh, Cu, Fe, Ni) supported on [...] Read more.

Catalytic combustion of hydrogen and ammonia containing off-gas surrogate from an ammonia solid oxide fuel cell (SOFC) was studied with a focus on nitrogen oxides (NO_x) mitigation. Noble and transition metals (Pt, Pd, Ir, Ru, Rh, Cu, Fe, Ni) supported on Al₂O₃ were tested in the range of 100 to 800 °C. The tested catalysts were able to completely convert hydrogen and ammonia present in the off-gas. The selectivity to NO_x increased with reaction temperature and stagnated at temperatures of 600 °C and higher. At low temperatures, the formation of N₂O was evident, which declined with increasing temperature until no N₂O was observed at temperatures exceeding 400 °C. Over nickel and iridium-based catalysts, the NO_x formation was reduced drastically, especially at 300 to 400 °C. To the best knowledge of the authors, the current paper is the first study about catalytic combustion of hydrogen-ammonia mixtures as a surrogate of an ammonia-fed SOFC off-gas. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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17 pages, 5371 KiB

Open AccessArticle

Effective Removal of Refractory Pollutants through Cinnamic Acid-Modified Wheat Husk Biochar: Experimental and DFT-Based Analysis

by Umme Habiba, Sadaf Mutahir, Muhammad Asim Khan, Muhammad Humayun, Moamen S. Refat and Khurram Shahzad Munawar

Catalysts 2022, 12(9), 1063; https://doi.org/10.3390/catal12091063 - 17 Sep 2022

Cited by 14 | Viewed by 2634

Abstract

The removal of refractory pollutants, i.e., methylene blue (MB) and ciprofloxacin (CIP), relies heavily on sorption technologies to address global demands for ongoing access to clean water. Because of the poor adsorbent–pollutant contact, traditional sorption procedures are inefficient. To accomplish this, a wheat [...] Read more.

The removal of refractory pollutants, i.e., methylene blue (MB) and ciprofloxacin (CIP), relies heavily on sorption technologies to address global demands for ongoing access to clean water. Because of the poor adsorbent–pollutant contact, traditional sorption procedures are inefficient. To accomplish this, a wheat husk biochar (WHB), loaded with cinnamic acid, was created using a simple intercalation approach to collect dangerous organic pollutants from an aqueous solution. Batch experiments, detecting technologies, and density functional theory (DFT) calculations were used to investigate the interactions at the wheat husk biochar modified with cinnamic acid (WHB/CA) and water interface to learn more about the removal mechanisms. With MB (96.52%) and CIP (94.03%), the functionalized WHB exhibited outstanding adsorption capabilities, with model fitting results revealing that the adsorption process was chemisorption and monolayer contact. Furthermore, DFT studies were performed to evaluate the interfacial interaction between MB and CIP with the WHB/CA surface. The orbital interaction diagram provided a visual representation of the interaction mechanism. These findings open up a new avenue for researchers to better understand adsorption behavior for the utilization of WHB on an industrial scale. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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9 pages, 1831 KiB

Open AccessArticle

CO Oxidation over Alumina-Supported Copper Catalysts

by Guoyan Ma, Le Wang, Xiaorong Wang, Lu Li and Hongfei Ma

Catalysts 2022, 12(9), 1030; https://doi.org/10.3390/catal12091030 - 10 Sep 2022

Cited by 3 | Viewed by 2259

Abstract

CO oxidation, one of the most important chemical reactions, has been commonly studied in both academia and the industry. It is one good probe reaction in the fields of surface science and heterogeneous catalysis, by which we can gain a better understanding and [...] Read more.

CO oxidation, one of the most important chemical reactions, has been commonly studied in both academia and the industry. It is one good probe reaction in the fields of surface science and heterogeneous catalysis, by which we can gain a better understanding and knowledge of the reaction mechanism. Herein, we studied the oxidation state of the Cu species to seek insight into the role of the copper species in the reaction activity. The catalysts were characterized by XRD, N₂ adsorption-desorption, X-ray absorption spectroscopy, and temperature-programmed reduction. The obtained results suggested that adding of Fe into the Cu/Al₂O₃ catalyst can greatly shift the light-off curve of the CO conversion to a much lower temperature, which means the activity was significantly improved by the Fe promoter. From the transient and temperature-programmed reduction experiments, we conclude that oxygen vacancy plays an important role in influencing CO oxidation activity. Adding Fe into the Cu/Al₂O₃ catalyst can remove part of the oxygen from the Cu species and form more oxygen vacancy. These oxygen vacancy sites are the main active sites for CO oxidation reaction and follow a Mars-van Krevelen-type reaction mechanism. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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20 pages, 9506 KiB

Open AccessArticle

Sr₂TiO₄ Prepared Using Mechanochemical Activation: Influence of the Initial Compounds’ Nature on Formation, Structural and Catalytic Properties in Oxidative Coupling of Methane

by Svetlana Pavlova, Yulia Ivanova, Sergey Tsybulya, Yurii Chesalov, Anna Nartova, Evgenii Suprun and Lyubov Isupova

Catalysts 2022, 12(9), 929; https://doi.org/10.3390/catal12090929 - 23 Aug 2022

Cited by 4 | Viewed by 1866

Abstract

Methane oxidative coupling (OCM) is considered a potential direct route to produce C₂ hydrocarbons. Layered perovskite-like Sr₂TiO₄ is a promising OCM catalyst. Mechanochemical activation (MA) is known to be an environmentally friendly method for perovskite synthesis. Sr₂TiO [...] Read more.

Methane oxidative coupling (OCM) is considered a potential direct route to produce C₂ hydrocarbons. Layered perovskite-like Sr₂TiO₄ is a promising OCM catalyst. Mechanochemical activation (MA) is known to be an environmentally friendly method for perovskite synthesis. Sr₂TiO₄ were synthesized using MA of the mixtures containing SrCO₃ or SrO and TiO₂ or TiO(OH)₂ and annealing at 900 and 1100 °C. XRD and FT-IRS showed that MA leads to the starting component disordering and formation of SrTiO₃ only for SrO being pronounced when using TiO(OH)₂. After annealing at 900 °C, Sr₂TiO₄ was mainly produced from the mixtures of SrCO₃ or SrO and TiO(OH)₂. The single-phase Sr₂TiO₄ was only obtained from MA products containing SrCO₃ after calcination at 1100 °C. The surface enrichment with Sr was observed by XPS for all samples annealed at 1100 °C depending on the MA product composition. The OCM activity of the samples correlated with the surface Sr concentration and the ratio of the surface oxygen amount in SrO and perovskite (O_o/O_p). The maximal CH₄ conversion and C₂ yield (25.6 and 15.5% at 900 °C, respectively), and the high long-term stability were observed for the sample obtained from (SrCO₃ + TiO₂), showing the specific surface morphology and optimal values of the surface Sr concentration and O_o/O_p ratio. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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16 pages, 3437 KiB

Open AccessArticle

Tungsten Trioxide and Its TiO₂ Mixed Composites for the Photocatalytic Degradation of NO_x and Bacteria (Escherichia coli) Inactivation

by Ermelinda Falletta, Claudia Letizia Bianchi, Franca Morazzoni, Alessandra Polissi, Flavia Di Vincenzo and Ignazio Renato Bellobono

Catalysts 2022, 12(8), 822; https://doi.org/10.3390/catal12080822 - 26 Jul 2022

Cited by 4 | Viewed by 1775

Abstract

The increased air pollution and its impact on the environment and human health in several countries have caused global concerns. Nitrogen oxides (NO₂ and NO) are principally emitted from industrial activities that strongly contribute to poor air quality. Among bacteria emanated from [...] Read more.

The increased air pollution and its impact on the environment and human health in several countries have caused global concerns. Nitrogen oxides (NO₂ and NO) are principally emitted from industrial activities that strongly contribute to poor air quality. Among bacteria emanated from the fecal droppings of livestock, wildlife, and humans, Escherichia coli is the most abundant, and is often associated with the health risk of water. TiO₂/WO₃ heterostructures represent emerging systems for photocatalytic environmental remediation. However, the results reported in the literature are conflicting, depending on several parameters. In this work, WO₃ and a series of TiO₂/WO₃ composites were properly synthesized by an easy and fast method, abundantly characterized by several techniques, and used for NO_x degradation and E. coli inactivation under visible light irradiation. We demonstrated that the photoactivity of TiO₂/WO₃ composites towards NO₂ degradation under visible light is strongly related to the WO₃ content. The best performance was obtained by a WO₃ load of 20% that guarantees limited e⁻/h⁺ recombination. On the contrary, we showed that E. coli could not be degraded under visible irradiation of the TiO₂/WO₃ composites. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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12 pages, 4559 KiB

Open AccessArticle

Strong Pyro-Electro-Chemical Coupling of Elbaite/H₂O₂ System for Pyrocatalysis Dye Wastewater

by Fei Chen, Jiesen Guo, Dezhong Meng, Yuetong Wu, Ruijin Sun and Changchun Zhao

Catalysts 2021, 11(11), 1370; https://doi.org/10.3390/catal11111370 - 13 Nov 2021

Cited by 7 | Viewed by 2485

Abstract

Elbaite is a natural silicate mineral with a spontaneous electric field. In the current study, it was selected as a pyroelectric catalyst to promote hydrogen peroxide (H₂O₂) for dye decomposition due to its pyro-electro-chemical coupling. The behaviors and efficiency [...] Read more.

Elbaite is a natural silicate mineral with a spontaneous electric field. In the current study, it was selected as a pyroelectric catalyst to promote hydrogen peroxide (H₂O₂) for dye decomposition due to its pyro-electro-chemical coupling. The behaviors and efficiency of the elbaite/H₂O₂ system in rhodamine B (RhB) degradation were systematically investigated. The results indicate that the optimal effective degradability of RhB reaches 100.0% at 4.0 g/L elbaite, 7.0 mL/L H₂O₂, and pH = 2.0 in the elbaite/H₂O₂ system. The elbaite/H₂O₂ system exhibits high recyclability and stability after recycling three times, reaching 94.5% of the degradation rate. The mechanisms of RhB degradation clarified that the hydroxyl radical (·OH) is the main active specie involved in catalytic degradation in the elbaite/H₂O₂ system. Moreover, not only does elbaite act as a pyroelectric catalyst to activate H₂O₂ in order to generate the primary ·OH for subsequent advanced oxidation reactions, but it also has the role of a dye sorbent. The elbaite/H₂O₂ system shows excellent application potential for the degradation of RhB. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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Review

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27 pages, 1968 KiB

Open AccessReview

The Role of Fungal Fuel Cells in Energy Production and the Removal of Pollutants from Wastewater

by Aisha Umar, Łukasz Smółka and Marek Gancarz

Catalysts 2023, 13(4), 687; https://doi.org/10.3390/catal13040687 - 31 Mar 2023

Cited by 8 | Viewed by 3878

Abstract

Pure water, i.e., a sign of life, continuously circulates and is contaminated by different discharges. This emerging environmental problem has been attracting the attention of scientists searching for methods for the treatment of wastewater contaminated by multiple recalcitrant compounds. Various physical and chemical [...] Read more.

Pure water, i.e., a sign of life, continuously circulates and is contaminated by different discharges. This emerging environmental problem has been attracting the attention of scientists searching for methods for the treatment of wastewater contaminated by multiple recalcitrant compounds. Various physical and chemical methods are used to degrade contaminants from water bodies. Traditional methods have certain limitations and complexities for bioenergy production, which motivates the search for new ways of sustainable bioenergy production and wastewater treatment. Biological strategies have opened new avenues to the treatment of wastewater using oxidoreductase enzymes for the degradation of pollutants. Fungal-based fuel cells (FFCs), with their catalysts, have gained considerable attention among scientists worldwide. They are a new, ecofriendly, and alternative approach to nonchemical methods due to easy handling. FFCs are efficiently used in wastewater treatment and the production of electricity for power generation. This article also highlights the construction of fungal catalytic cells and the enzymatic performance of different fungal species in energy production and the treatment of wastewater. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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22 pages, 1378 KiB

Open AccessReview

A Systematic Review on Solar Heterogeneous Photocatalytic Water Disinfection: Advances over Time, Operation Trends, and Prospects

by Felipe de J. Silerio-Vázquez, Cynthia M. Núñez-Núñez, José B. Proal-Nájera and María T. Alarcón-Herrera

Catalysts 2022, 12(11), 1314; https://doi.org/10.3390/catal12111314 - 26 Oct 2022

Cited by 4 | Viewed by 2279

Abstract

Access to drinking water is a human right recognized by the United Nations. It is estimated that more than 2.1 billion people lack access to drinking water with an adequate microbiological quality, which is associated to 80% of all diseases, as well as [...] Read more.

Access to drinking water is a human right recognized by the United Nations. It is estimated that more than 2.1 billion people lack access to drinking water with an adequate microbiological quality, which is associated to 80% of all diseases, as well as with millions of deaths caused by infections, especially in children. Water disinfection technologies need a continuous improvement approach to meet the growing demand caused by population growth and climate change. Heterogeneous photocatalysis with semiconductors, which is an advanced oxidation process, has been proposed as a sustainable technology for water disinfection, as it does not need addition of any chemical substance and it can make use of solar light. Nevertheless, the technology has not been deployed industrially and commercially yet, mainly because of the lack of efficient reactor designs to treat large volumes of water, as most research focus on lab-scale experimentation. Additionally, very few applications are often tested employing actual sunlight. The present work provide a perspective on the operation trends and advances of solar heterogeneous photocatalytic reactors for water disinfection by systematically analyzing pertaining literature that made actual use of sunlight, with only 60 reports found out of the initially 1044 papers detected. These reports were discussed in terms of reactor employed, photocatalyst used, microorganism type, overall disinfection efficiency, and location. General prospects for the progression of the technology are provided as well. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

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