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Editorial

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4 pages, 209 KiB

Open AccessEditorial

Photocatalytic Oxidation/Ozonation Processes

by Juan F. García-Araya and Fernando J. Beltrán

Catalysts 2023, 13(2), 314; https://doi.org/10.3390/catal13020314 - 01 Feb 2023

Cited by 2 | Viewed by 994

Abstract

Diffuse pollution and the presence in waters of so-called emerging pollutants, among others, represent a major global environmental problem [...] Full article

(This article belongs to the Special Issue Photocatalytic Oxidation/Ozonation Processes)

Research

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12 pages, 2343 KiB

Open AccessFeature PaperArticle

Six Flux Model for the Central Lamp Reactor Applied to an External Four-Lamp Reactor

by Fernando J. Beltrán, Javier Rivas and Juan-Fernando Garcia-Araya

Catalysts 2021, 11(10), 1190; https://doi.org/10.3390/catal11101190 - 29 Sep 2021

Cited by 2 | Viewed by 1226

Abstract

One of the difficulties of establishing the intrinsic kinetics of photocatalytic oxidation processes is due to the complex mathematical formula used to determine the rate of photon absorption. To solve this problem, some models have been proposed and checked, such as the Six [...] Read more.

One of the difficulties of establishing the intrinsic kinetics of photocatalytic oxidation processes is due to the complex mathematical formula used to determine the rate of photon absorption. To solve this problem, some models have been proposed and checked, such as the Six Flux Model (SFM) confirmed in central lamp photoreactors. External lamp photoreactors are also one of the most used configurations to study the photocatalytic oxidation of contaminants in water, and complex mathematical solutions have been reported to solve the rate of photon absorption. In this work, SFM Equations already reported for the central lamp photoreactor have been adapted to determine the rate of photon absorption in an external four-lamp photoreactor. The results obtained show slight differences from those of the Monte Carlo method. Additionally, once the rate of photon absorption was validated, the intrinsic rate constant and scavenging factor of the photocatalytic oxidation of some contaminant compounds from results already published have been determined. Full article

(This article belongs to the Special Issue Photocatalytic Oxidation/Ozonation Processes)

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16 pages, 3110 KiB

Open AccessArticle

Enhanced Naproxen Elimination in Water by Catalytic Ozonation Based on NiO Films

by Claudia M. Aguilar-Melo, Julia L. Rodríguez, Isaac Chairez, Iván Salgado, J. A. Andraca Adame, J. A. Galaviz-Pérez, Jorge Vazquez-Arenas and Tatyana Poznyak

Catalysts 2020, 10(8), 884; https://doi.org/10.3390/catal10080884 - 05 Aug 2020

Cited by 5 | Viewed by 2582

Abstract

This study evaluates naproxen (NP) degradation efficiency by ozonation using nickel oxide films (

N i O_{(F)}

) as a catalyst. The NiO films were synthesized by chemical vapor deposition and characterized by X-ray diffraction, scanning electron microscopy, atomic force [...] Read more.

This study evaluates naproxen (NP) degradation efficiency by ozonation using nickel oxide films (

N i O_{(F)}

) as a catalyst. The NiO films were synthesized by chemical vapor deposition and characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. NP degradation was conducted for 5 min using 10 films of

N i O_{(F)}

comparing against ozonation using 100 mg/L

N i O

powder in suspension (

N i O_{(S)}

) and conventional ozonation (

O_{3}

-conv). Total organic carbon analysis demonstrated a mineralization degree of 12% with

O_{3}

-conv, 35% with

N i O

as powder and 22% with

N i O_{(F)}

after 60 min of reaction. The films of

N i O_{(F)}

were sequentially used 4 times in ozonation demonstrating the stability of the synthesized material, as well as its properties as a catalyst for ozonation. A proposed modeling strategy using robust parametric identification techniques allows the comparison of NP decomposition pseudo-monomolecular reaction rates. Full article

(This article belongs to the Special Issue Photocatalytic Oxidation/Ozonation Processes)

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9 pages, 1930 KiB

Open AccessArticle

Oxidative Dehydrogenation of Methane When Using TiO₂- or WO₃-Doped Sm₂O₃ in the Presence of Active Oxygen Excited with UV-LED

by Shigeru Sugiyama, Yasunori Hayashi, Ikumi Okitsu, Naohiro Shimoda, Masahiro Katoh, Akihiro Furube, Yuki Kato and Wataru Ninomiya

Catalysts 2020, 10(5), 559; https://doi.org/10.3390/catal10050559 - 18 May 2020

Cited by 3 | Viewed by 2798

Abstract

There are active oxygen species that contribute to oxidative coupling or the partial oxidation during the oxidative dehydrogenation of methane when using solid oxide catalysts, and those species have not been definitively identified. In the present study, we clarify which of the active [...] Read more.

There are active oxygen species that contribute to oxidative coupling or the partial oxidation during the oxidative dehydrogenation of methane when using solid oxide catalysts, and those species have not been definitively identified. In the present study, we clarify which of the active oxygen species affect the oxidative dehydrogenation of methane by employing photo-catalysts such as TiO₂ or WO₃, which generate active oxygen from UV-LED irradiation conditions under an oxygen flow. These photo-catalysts were studied in combination with Sm₂O₃, which is a methane oxidation coupling catalyst. For this purpose, we constructed a reaction system that could directly irradiate UV-LED to a solid catalyst via a normal fixed-bed continuous-flow reactor operated at atmospheric pressure. Binary catalysts prepared from TiO₂ or WO₃ were either supported on or kneaded with Sm₂O₃ in the present study. UV-LED irradiation clearly improved the partial oxidation from methane to CO and/or slightly improved the oxidative coupling route from methane to ethylene when binary catalysts consisting of Sm₂O₃ and TiO₂ are used, while negligible UV-LED effects were detected when using Sm₂O₃ and WO₃. These results indicate that with UV-LED irradiation the active oxygen of O₂⁻ from TiO₂ certainly contributes to the activation of methane during the oxidative dehydrogenation of methane when using Sm₂O₃, while the active oxygen of H₂O₂ from WO₃ under the same conditions afforded only negligible effects on the activation of methane. Full article

(This article belongs to the Special Issue Photocatalytic Oxidation/Ozonation Processes)

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12 pages, 3358 KiB

Open AccessArticle

Potassium Ferrite as Heterogeneous Photo-Fenton Catalyst for Highly Efficient Dye Degradation

by Xinghui Zhang, Zhibin Geng, Juan Jian, Yiqiang He, Zipeng Lv, Xinxin Liu and Hongming Yuan

Catalysts 2020, 10(3), 293; https://doi.org/10.3390/catal10030293 - 04 Mar 2020

Cited by 20 | Viewed by 3440

Abstract

In this work, hexagon-shaped potassium ferrite (K₂Fe₄O₇) crystals with different sizes were prepared using the hydrothermal method. The crystals showed a narrow band gap of 1.44 eV, revealed by UV-visible diffuse reflectance spectroscopy, and was thus used [...] Read more.

In this work, hexagon-shaped potassium ferrite (K₂Fe₄O₇) crystals with different sizes were prepared using the hydrothermal method. The crystals showed a narrow band gap of 1.44 eV, revealed by UV-visible diffuse reflectance spectroscopy, and was thus used as a heterogeneous Fenton catalyst to degrade methylene blue (MB) and crystal violet (CV) in the presence of green oxidant H₂O₂ under visible-light irradiation. Among the investigated crystals, the as-prepared one with an average size of 20 µm (KFO-20) exhibited better photocatalytic activity due to its high surface area. When it was used as a photo-Fenton catalyst, 100% MB and 92% CV were degraded within 35 min. Moreover, the catalyst maintained high photocatalytic activity and was stable after four continuous cycles. The trapping experiments showed that the active hydroxyl radical (·OH) was dominant in the photo-Fenton reaction. Therefore, this new photo-Fenton catalyst has great potential for the photocatalytic degradation of dye contaminants in water. Full article

(This article belongs to the Special Issue Photocatalytic Oxidation/Ozonation Processes)

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12 pages, 3382 KiB

Open AccessArticle

Photocatalytic Oxidation of Methyl Tert-Butyl Ether in Presence of Various Phase Compositions of TiO₂

by Marcel Šihor, Martin Reli, Michal Vaštyl, Květoslava Hrádková, Lenka Matějová and Kamila Kočí

Catalysts 2020, 10(1), 35; https://doi.org/10.3390/catal10010035 - 26 Dec 2019

Cited by 5 | Viewed by 2648

Abstract

MTBE (methyl tert-butyl ether) represents a rising threat to the environment, especially drinking water, and its effective removal (with all by-products) is necessary. Even a very low concentration of MTBE makes the water undrinkable; therefore, an effective treatment has to be developed. [...] Read more.

MTBE (methyl tert-butyl ether) represents a rising threat to the environment, especially drinking water, and its effective removal (with all by-products) is necessary. Even a very low concentration of MTBE makes the water undrinkable; therefore, an effective treatment has to be developed. This work is focused on MTBE photocatalytic oxidation in presence of various TiO₂ photocatalysts with different phase composition prepared by different methods. It was confirmed the phase composition of TiO₂ had the most significant influence on the photocatalytic degradation of MTBE. The rutile phase more easily reduces adsorbed oxygen by photogenerated electrons to superoxide radical, supporting separation of charge carriers. The presence and concentrations of by-products have to be taken into account as well. The conversion of total organic carbon (TOC) was used for the comparison, 40% of TOC was removed after 1 h of irradiation in presence of TiO₂–ISOP–C/800 photocatalyst composed of anatase and rutile phase. Full article

(This article belongs to the Special Issue Photocatalytic Oxidation/Ozonation Processes)

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12 pages, 5473 KiB

Open AccessArticle

Enhanced Photocatalytic Ozonation of Phenol by Ag/ZnO Nanocomposites

by Junmin Peng, Tong Lu, Hongbo Ming, Zhengxin Ding, Zhiyang Yu, Jinshui Zhang and Yidong Hou

Catalysts 2019, 9(12), 1006; https://doi.org/10.3390/catal9121006 - 30 Nov 2019

Cited by 22 | Viewed by 4317

Abstract

Ag/ZnO nanocomposites were synthesized and applied in the photocatalytic ozonation of phenol. Their crystal, textural, morphological, optical, and electrochemical properties were investigated by XRD, Raman, SEM, TEM, UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoemission spectroscopy (XPS), and photoluminescence (PL) techniques in detail. The [...] Read more.

Ag/ZnO nanocomposites were synthesized and applied in the photocatalytic ozonation of phenol. Their crystal, textural, morphological, optical, and electrochemical properties were investigated by XRD, Raman, SEM, TEM, UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoemission spectroscopy (XPS), and photoluminescence (PL) techniques in detail. The results indicated that silver nanoparticles were well dispersed on the surface of porous ZnO and the intimate contacts were formed at the Ag/ZnO interfaces. This prominently favored the separation and transfer of photoinduced electrons from ZnO to Ag nanoparticles for the activation of ozone to produce •OH and •O₂⁻. As a result, a significant enhancement in photocatalytic ozonation of phenol was achieved over Ag/ZnO catalysts. It also showed a synergistic effect between photocatalysis and ozonation. Full article

(This article belongs to the Special Issue Photocatalytic Oxidation/Ozonation Processes)

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Review

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63 pages, 3027 KiB

Open AccessFeature PaperReview

The Role of Catalytic Ozonation Processes on the Elimination of DBPs and Their Precursors in Drinking Water Treatment

by Fernando J. Beltrán, Ana Rey and Olga Gimeno

Catalysts 2021, 11(4), 521; https://doi.org/10.3390/catal11040521 - 20 Apr 2021

Cited by 20 | Viewed by 3729

Abstract

Formation of disinfection byproducts (DBPs) in drinking water treatment (DWT) as a result of pathogen removal has always been an issue of special attention in the preparation of safe water. DBPs are formed by the action of oxidant-disinfectant chemicals, mainly chlorine derivatives (chlorine, [...] Read more.

Formation of disinfection byproducts (DBPs) in drinking water treatment (DWT) as a result of pathogen removal has always been an issue of special attention in the preparation of safe water. DBPs are formed by the action of oxidant-disinfectant chemicals, mainly chlorine derivatives (chlorine, hypochlorous acid, chloramines, etc.), that react with natural organic matter (NOM), mainly humic substances. DBPs are usually refractory to oxidation, mainly due to the presence of halogen compounds so that advanced oxidation processes (AOPs) are a recommended option to deal with their removal. In this work, the application of catalytic ozonation processes (with and without the simultaneous presence of radiation), moderately recent AOPs, for the removal of humic substances (NOM), also called DBPs precursors, and DBPs themselves is reviewed. First, a short history about the use of disinfectants in DWT, DBPs formation discovery and alternative oxidants used is presented. Then, sections are dedicated to conventional AOPs applied to remove DBPs and their precursors to finalize with the description of principal research achievements found in the literature about application of catalytic ozonation processes. In this sense, aspects such as operating conditions, reactors used, radiation sources applied in their case, kinetics and mechanisms are reviewed. Full article

(This article belongs to the Special Issue Photocatalytic Oxidation/Ozonation Processes)

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26 pages, 5868 KiB

Open AccessEditor’s ChoiceReview

Review on the Visible Light Photocatalysis for the Decomposition of Ciprofloxacin, Norfloxacin, Tetracyclines, and Sulfonamides Antibiotics in Wastewater

by Samar Shurbaji, Pham Thi Huong and Talal Mohammed Altahtamouni

Catalysts 2021, 11(4), 437; https://doi.org/10.3390/catal11040437 - 29 Mar 2021

Cited by 66 | Viewed by 6257

Abstract

Antibiotics are chemical compounds that are used to kill or prevent bacterial growth. They are used in different fields, such as the medical field, agriculture, and veterinary. Antibiotics end up in wastewater, which causes the threat of developing antibacterial resistance; therefore, antibiotics must [...] Read more.

Antibiotics are chemical compounds that are used to kill or prevent bacterial growth. They are used in different fields, such as the medical field, agriculture, and veterinary. Antibiotics end up in wastewater, which causes the threat of developing antibacterial resistance; therefore, antibiotics must be eliminated from wastewater. Different conventional elimination methods are limited due to their high cost and effort, or incomplete elimination. Semiconductor-assisted photocatalysis arises as an effective elimination method for different organic wastes including antibiotics. A variety of semiconducting materials were tested to eliminate antibiotics from wastewater; nevertheless, research is still ongoing due to some limitations. This review summarizes the recent studies regarding semiconducting material modifications for antibiotic degradation using visible light irradiation. Full article

(This article belongs to the Special Issue Photocatalytic Oxidation/Ozonation Processes)

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