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Environmental Catalysis in Advanced Oxidation Processes

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A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Environmental Catalysis".

Deadline for manuscript submissions: closed (31 August 2022) | Viewed by 25838

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Special Issue Editors

Prof. Dr. Albin Pintar

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Department of Inorganic Chemistry and Technology, National Institute of Chemistry, Hajdrihova 19, SI-1001 Ljubljana, Slovenia
Interests: heterogeneous catalysis; environmental catalysis; reaction kinetics and mechanisms; synthesis and characterization of catalysts; process development and intensification
Special Issues, Collections and Topics in MDPI journals

Dr. Gregor Žerjav

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Department of Inorganic Chemistry and Technology, National Institute of Chemistry, Hajdrihova 19, SI-1001 Ljubljana, Slovenia
Interests: photocatalysis; heterogeneous catalysis; advanced oxidation processes; visible-light-driven photocatalysts; photocatalysis for water purification; photocatalysts based on TiO₂; preparation and characterization of catalysts and materials; water treatment by advanced oxidation processes
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear colleagues,

Population growth, industry development, and an increase in agriculture are connected with the release into the environment of a large number of toxic pollutants, which cannot be degraded by natural means. In the last few decades, a group of chemical oxidative technologies classified as advanced oxidation processes (AOPs) have received significant interest as pollution removal applications. AOPs are based on generation of highly reactive and non-selective hydroxyl radicals (OH∙). There are several approaches to the generation of hydroxyl radicals, such as Fenton-, UV-, and ozone-based processes as well as heterogeneous photocatalytic processes.

We invite authors to submit original research papers focused on the synthesis and characterization of novel heterogeneous catalysts and their utilization in AOPs for the removal of complex organic and recalcitrant contaminants from the environment. Particular interest will be given to papers that explore novel reactor systems and field applications of AOPs.

Prof. Dr. Albin Pintar
Dr. Gregor Žerjav
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

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Keywords

Advanced oxidation processes
Heterogeneous catalysis/photocatalysis
Water/air treatment
Organic pollutants
Novel catalysts for catalytic/photocatalytic AOPs
In situ and operando catalyst characterization
Reaction mechanisms and kinetics
Pilot-scale studies and field applications

Related Special Issue

Environmental Catalysis in Advanced Oxidation Processes, 2nd Edition in Catalysts (4 articles)

Published Papers (9 papers)

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Research

16 pages, 5643 KiB

Open AccessArticle

Olive Mill Wastewater (OMW) Treatment Using Photocatalyst Media

by Abeer Al Bawab, Muna Abu-Dalo, Aya Khalaf and Duaa Abu-Dalo

Catalysts 2022, 12(5), 539; https://doi.org/10.3390/catal12050539 - 15 May 2022

Cited by 4 | Viewed by 2502

Abstract

A new nanophotocatalysts series of M₂Zr₂O₇ (M = Mn, Cu, and Fe) and doped Fe₂Zr₂O₇ systems were prepared via sol-gel using the pechini method, characterized, and tested in photocatalytic degradation of olive mill wastewater (OMW). The photocatalytic degradation of the prepared materials was evaluated by measuring total phenolic compounds (TPCs) using the Folin-Ciocalteu method for variable pH under a commercial LED lamp (45 W). The removal of TPCs was measured at different contact times ranging from 2 h to 6 days. X-ray diffraction (XRD) and transmission electron microscope (TEM) analysis approved the nano size of (5–17 nm) and quasi-spherical morphology of the prepared materials. ICP-OES analysis confirmed the XRD analysis and approved the structure of the prepared materials. Aggregation of the nanomaterials was observed using TEM imaging. Brunauer-Emmett-Teller (BET) analysis measured a 67 m²/g surface area for Fe₂Zr₂O₇. Doping Fe with Mn increased the surface area to 173 m²/g and increased to 187 m²/g with a further increase of the Mn dopant. Increasing the Mn dopant concentration increased both surface area and photocatalytic degradation. The highest degradation of TPCs was observed for Mn₂Zr₂O₇ around 70% at pH 10 and exposure time up to one day. Full article

(This article belongs to the Special Issue Environmental Catalysis in Advanced Oxidation Processes)

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14 pages, 3336 KiB

Open AccessArticle

Structure and Photocatalytic Activity of Copper and Carbon-Doped Metallic Zn Phase-Rich ZnO Oxide Films

by Simona Tuckute, Sarunas Varnagiris, Marius Urbonavicius, Emilija Demikyte, Kristina Bockute and Martynas Lelis

Catalysts 2022, 12(1), 60; https://doi.org/10.3390/catal12010060 - 06 Jan 2022

Cited by 1 | Viewed by 1624

Abstract

ZnO is one of the most important industrial metal oxide semiconductors. However, in order to fully realise its potential, the electronic structure of ZnO has to be modified to better fit the needs of specific fields. Recent studies demonstrated that reactive magnetron sputtering under Zn-rich conditions promotes the formation of intrinsic ZnO defects and allows the deposition of metallic Zn phase-rich ZnO films. In photocatalytic efficiency tests these films were superior to traditional ZnO oxide, therefore, the purposeful formation of intrinsic ZnO defects, namely Zn interstitials and oxygen vacancies, can be considered as advantageous self-doping. Considering that such self-doped ZnO remains a semiconductor, the natural question is if it is possible to further improve its properties by adding extrinsic dopants. Accordingly, in the current study, the metallic Zn phase-rich ZnO oxide film formation process (reactive magnetron sputtering) was supplemented by simultaneous sputtering of copper or carbon. Effects of the selected dopants on the structure of self-doped ZnO were investigated by X-ray diffractometer, scanning electron microscope, X-ray photoelectron spectroscope and photoluminescence techniques. Meanwhile, its effect on photocatalytic activity was estimated by visible light activated bleaching of Methylene Blue. It was observed that both dopants modify the microstructure of the films, but only carbon has a positive effect on photocatalytic efficiency. Full article

(This article belongs to the Special Issue Environmental Catalysis in Advanced Oxidation Processes)

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15 pages, 2459 KiB

Open AccessArticle

Influence of the Metabolic Activity of Microorganisms on Disinfection Efficiency of the Visible Light and P25 TiO₂ Photocatalyst

by Sandra Sakalauskaite, Deimante Vasiliauske, Emilija Demikyte, Rimantas Daugelavicius and Martynas Lelis

Catalysts 2021, 11(12), 1432; https://doi.org/10.3390/catal11121432 - 25 Nov 2021

Cited by 3 | Viewed by 1308

Abstract

The beneficial photocatalytic properties of UV light activated TiO₂ powder are well-known and have been demonstrated with various pollutants and pathogens. However, traditionally observed photocatalytic activity of visible light activated pristine TiO₂ is insignificant but there are a few studies which have reported that under some specific conditions commercially available TiO₂ powder could at least partially disinfect microorganisms even under visible light. To better understand this phenomenon, in the current study we focused on bacteria response to the treatment by visible light and P25 TiO₂ powder. More specifically, we analyzed the relationship between the bacteria viability, outer membrane permeability, metabolism, and its capacity to generate intracellular reactive oxygen species. During the study we assayed the viability of treated bacteria by the spread plate technique and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction method. Changes in bacterial outer membrane permeability were determined by measuring the fluorescence of N-phenyl-1-naphthylamine (NPN). To detect intracellular reactive oxygen species formation, the fluorescence of dichlorodihydrofluorescein diacetate (DCFH-DA) was assayed. Results of our study indicated that TiO₂ and wide spectrum visible light irradiation damaged the integrity of the outer membrane and caused oxidative stress in the metabolizing bacteria. When favorable conditions were created, these effects added up and unexpectedly high bacterial inactivation was achieved. Full article

(This article belongs to the Special Issue Environmental Catalysis in Advanced Oxidation Processes)

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12 pages, 3907 KiB

Open AccessArticle

Removal of Nonylphenol Polyethylene Glycol (NPEG) with Au-TiO₂ Catalysts: Kinetic and Initial Transformation Path

by Claudia Aguilar, Mayra Garcia, Carlos Montalvo, Francisco Anguebes, Edgar Moctezuma, Mohamed Abatal and Sandra Figueroa

Catalysts 2020, 10(10), 1205; https://doi.org/10.3390/catal10101205 - 17 Oct 2020

Viewed by 2104

Abstract

The purpose of this study was to evaluate the efficiency of the Au-TiO₂ catalyst in the degradation of nonylphenol polyethylene glycol (NPEG). In the first part of the study, the catalyst was synthesized and characterized. Initially, the catalyst (TiO₂ Degussa P-25) was doped with gold precursor salts (HAuCl₄) at different concentrations (5, 10, and 15%) and the photodeposition method with UV light. It was determined by diffuse reflectance (DF) and scanning electron microscopy (SEM) that the photodeposition method was effective for the inclusion of gold particles on the surface. The catalyst band gap showed a reduction to 2.9 e.v (compared to TiO₂ Degussa P-25), and it was observed that the gold-doped catalyst showed absorption in the visible light range 500 to 600 nm. The percentage of deposited gold was determined by energy dispersive spectroscopy (EDS). In the second part of the study, various NPEG degradation experiments were performed; with the catalyst that showed the best conversion percentages of NPEG, the experimental data were analyzed using UV-Vis spectrophotometry and TOC (total organic carbon). With these results, a carbon-based mass balance and reaction kinetics were generated using the Langmuir–Hinshelwood (L–H) heterogeneous catalysis model. For the estimation of the kinetic constants, the non-linear regression of the Levenger–Marquardt algorithm was used. With these results, kinetic models of the degradation of the molecule and the generation and consumption of organic intermediate products (OIPs) were generated. Full article

(This article belongs to the Special Issue Environmental Catalysis in Advanced Oxidation Processes)

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16 pages, 3258 KiB

Open AccessArticle

The Influence of a Surface Treatment of Metallic Titanium on the Photocatalytic Properties of TiO₂ Nanotubes Grown by Anodic Oxidation

by Živa Marinko, Luka Suhadolnik, Zoran Samardžija, Janez Kovač and Miran Čeh

Catalysts 2020, 10(7), 803; https://doi.org/10.3390/catal10070803 - 19 Jul 2020

Cited by 1 | Viewed by 2771

Abstract

Titanium dioxide (TiO₂) nanotubes obtained by the anodic oxidation of titanium metal foils can be used for the photocatalytic degradation of organic pollutants. The aim of our study was to determine the influence of the titanium foil’s surface treatment on the final morphology of the TiO₂ nanotubes and their photocatalytic activity. In our experiments, we used two different titanium foils that were electropolished or untreated prior to the anodic oxidation. The morphologies of the starting titanium foils and the resulting TiO₂ nanotube layers were investigated and the photocatalytic activities measured by the decomposition of caffeine under UV irradiation. Our results showed that electropolishing of the starting foils produced a more uniform and smoother TiO₂ nanotubes surface. In contrast, the TiO₂ nanotube surfaces from untreated titanium foils mimic the initial surface roughness of the titanium foil. A comparison of the photocatalytic properties of the TiO₂ nanotube layers obtained from the untreated and electropolished titanium foils showed that electropolishing does not necessarily improve the photocatalytic properties of the resulting TiO₂ nanotube layer. It was found that the determining factors influencing the photocatalytic activity are the chemical impurities (Ti-nitride) on the surface of the titanium foils and the surface roughness of the TiO₂ nanotube layer. The highest photocatalytic activity was achieved with the anodized untreated foil with the minimal presence of Ti-nitride and a relatively high roughness of the TiO₂ nanotubes. Full article

(This article belongs to the Special Issue Environmental Catalysis in Advanced Oxidation Processes)

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16 pages, 4112 KiB

Open AccessFeature PaperArticle

Influence of TiO₂ Morphology and Crystallinity on Visible-Light Photocatalytic Activity of TiO₂-Bi₂O₃ Composite in AOPs

by Gregor Žerjav and Albin Pintar

Catalysts 2020, 10(4), 395; https://doi.org/10.3390/catal10040395 - 03 Apr 2020

Cited by 8 | Viewed by 2618

Abstract

Solution combustion synthesis was used to produce a junction between different TiO₂ supports (anatase TiO₂ nanorods (TNR) and nanoparticles (TNP) and TiO₂ with anatase core and amorphous shell (a-TNR)) and narrow bandgap (BG) semiconductor β-Bi₂O₃. β-Bi₂O₃ acted as a visible-light photosensitizer and enabled us to carry out photocatalytic oxidation of water dissolved bisphenol A (BPA) with TiO₂ based catalysts under visible-light illumination. Heterojunction between TiO₂ and β-Bi₂O₃ in TNR + Bi and TNP + Bi composites enables the transfer of visible-light generated holes from the β-Bi₂O₃ valence band (VB) to the upper lying TiO₂ VB. A p–n junction, established upon close chemical contact between TiO₂ and β-Bi₂O₃, enables the transfer of visible-light generated electrons in the β-Bi₂O₃ conduction band (CB) to the TiO₂ CB. In TNR + Bi and a-TNR + Bi composites, the supplied heat energy during the synthesis of samples was not sufficient to completely transform (BiO)₂CO₃ into β-Bi₂O₃. A p–n junction between (BiO)₂CO₃ and β-Bi₂O₃ enables the transfer of electrons generated by β-Bi₂O₃ to (BiO)₂CO₃. Hindered charge carrier recombination originating from the crystallinity of TiO₂ is a more important factor in the overall kinetics of BPA degradation than high specific surface area of the amorphous TiO₂ and reduction/oxidation of surface adsorbed substrates. Full article

(This article belongs to the Special Issue Environmental Catalysis in Advanced Oxidation Processes)

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18 pages, 3570 KiB

Open AccessArticle

SnO₂-Containing Clinoptilolite as a Composite Photocatalyst for Dyes Removal from Wastewater under Solar Light

by Andraž Šuligoj, Jelena Pavlović, Iztok Arčon, Nevenka Rajić and Nataša Novak Tušar

Catalysts 2020, 10(2), 253; https://doi.org/10.3390/catal10020253 - 19 Feb 2020

Cited by 24 | Viewed by 3085

Abstract

Due to their adsorbent, ion exchange and catalytic properties zeolites are suitable for a variety of applications. We report on the photocatalytic activity of a readily available and inexpensive natural zeolite clinoptilolite (Z) containing SnO₂ (Sn-Z). The Sn-Z samples with 3–15 wt. % of Sn were prepared by using a precipitation–deposition method. Powder X-ray diffraction analysis showed that the zeolite structure was unaffected by the introduction of the Sn-phase. Diffuse reflectance UV/VIS spectra of the Sn-Z samples confirmed the presence of SnO₂ and X-Ray absorption spectroscopy analyses suggested that the SnO₂ particles mainly resided on the surface of the clinoptilolite, while ATR-FTIR analysis gave some clues that part of the SnO₂ phase was incorporated in the pores of the zeolite. The presence of SnO₂ in Sn-Z increased both adsorption capacity and photocatalytic performance which could be partially explained by higher surface area and partially with an increased negative potential of the surface. Adsorption and total degradation of methylene blue (MB) for the Sn-Z with the highest amount of Sn (15 wt.%) was about 30% and 45%, respectively, suggesting a synergetic effect between SnO₂ and the clinoptilolite lattice. Reusability tests showed that these catalysts present a promising material for water purification. Full article

(This article belongs to the Special Issue Environmental Catalysis in Advanced Oxidation Processes)

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15 pages, 5219 KiB

Open AccessArticle

Acceleration of Persulfate Activation by MIL-101(Fe) with Vacuum Thermal Activation: Effect of FeII/FeIII Mixed-Valence Center

by Jieyang Yang, Zequan Zeng, Zhanggen Huang and Yan Cui

Catalysts 2019, 9(11), 906; https://doi.org/10.3390/catal9110906 - 29 Oct 2019

Cited by 15 | Viewed by 3592

Abstract

In this work, the activation effect of vacuum thermal treatment on MIL-101(Fe) (MIL: Materials of Institute Lavoisier) was investigated for the first time. It demonstrated that vacuum thermal activation could accelerate the activation of persulfate (PS) by MIL-101(Fe), and the enhancement of the catalytic capacity of MIL-101(Fe) was mainly attributed to the change in the FeII/FeIII mixed-valence center. The results of the SEM and XRD showed that vacuum thermal activation had a negligible effect on the crystal structure and particle morphology of MIL-101(Fe). Meanwhile, the higher temperature of vacuum thermal activation caused a higher relative content ratio of FeII/FeIII. A widely used azo dye, X-3B, was chosen as the probe molecule to investigate the catalytic performance of all samples. The results showed that the activated samples could remove X-3B more effectively, and the sample activated at 150 °C without regeneration could effectively activate PS to remove X-3B for at least 5 runs and approximately 900 min. This work highlights the often-overlooked activation effect of vacuum thermal treatment and provides a simple way to improve the catalytic capacity and reusability of MIL-101(Fe) which is beneficial for the application of MIL-101(Fe)/PS systems in azo dye wastewater treatment. Full article

(This article belongs to the Special Issue Environmental Catalysis in Advanced Oxidation Processes)

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17 pages, 2920 KiB

Open AccessArticle

Activated Carbon as a Cathode for Water Disinfection through the Electro-Fenton Process

by Long Chen, Ameet Pinto and Akram N. Alshawabkeh

Catalysts 2019, 9(7), 601; https://doi.org/10.3390/catal9070601 - 12 Jul 2019

Cited by 15 | Viewed by 4808

Abstract

Unlike many other water disinfection methods, hydroxyl radicals (HO^•) produced by the Fenton reaction (Fe²⁺/H₂O₂) can inactivate pathogens regardless of taxonomic identity of genetic potential and do not generate halogenated disinfection by-products. Hydrogen peroxide (H₂O₂) required for the process is typically electrogenerated using various carbonaceous materials as cathodes. However, high costs and necessary modifications to the cathodes still present a challenge to large-scale implementation. In this work, we use granular activated carbon (GAC) as a cathode to generate H₂O₂ for water disinfection through the electro-Fenton process. GAC is a low-cost amorphous carbon with abundant oxygen- and carbon-containing groups that are favored for oxygen reduction into H₂O₂. Results indicate that H₂O₂ production at the GAC cathode is higher with more GAC, lower pH, and smaller reactor volume. Through the addition of iron ions, the electrogenerated H₂O₂ is transformed into HO^• that efficiently inactivated model pathogen (Escherichia coli) under various water chemistry conditions. Chick–Watson modeling results further showed the strong lethality of produced HO^• from the electro-Fenton process. This inactivation coupled with high H₂O₂ yield, excellent reusability, and relatively low cost of GAC proves that GAC is a promising cathodic material for large-scale water disinfection. Full article

(This article belongs to the Special Issue Environmental Catalysis in Advanced Oxidation Processes)

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