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Photo/Electrocatalysis for Wastewater Treatment

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

Deadline for manuscript submissions: closed (10 July 2022) | Viewed by 34508

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Special Issue Editors

Dr. Aida M. Diez

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Guest Editor

Nanochemistry research group, International Iberian Nanotechnology Laboratory (INL), Avda. Mestre José Veiga s/n, 4715-330, Braga, Portugal
Interests: Advanced Oxidation Processes combination for organic pollutants abatement; real wastewaters treatment; reactor set-up for performance enhancement; synthesis of new photocatalyst based on TiO2; adsorption with inexpensive materials and their regeneration process; photocatalytic plastic degradation; water splitting and CO2 photo-reduction

Dr. Vitor J. P. Vilar

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Guest Editor

Associate Laboratory LSRE-LCM (Laboratory of Separation and Reaction Engineering - Laboratory of Catalysis and Materials), Faculty of Engineering University of Porto, R. Dr. Roberto Frias s/n, 4200-465 Porto, Portugal
Interests: environmental assessment and monitoring of surface waters; environmental friendly technologies for pollution control; advanced oxidation processes; electrochemical advanced oxidation processes, ozonation, membrane filtration, sorption/biosorption, biological degradation, process integration and intensification; water/waste reuse, recycling and valorisation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Researchers,

A wide array of wastewater treatment alternatives are being investigated nowadays, which is in harmony with the increase in polluted wastewater generation due to the growth in population and industrial activities.

Advanced oxidation processes (AOPs) have become in the last few years a selected alternative due to several advantages, such as their non-selective degradation of pollutants and their easy setup. Photo-based processes have always been one of the most preferred AOP options, due to the possibility of using solar radiation which may reduce the AOPs’ high elevated costs.

Nevertheless, photolysis is usually inefficient for pollutant degradation, due to the lack of radiation adsorption of the vast majority of compounds, and even in the case when pollutant is photo-active, the degradation rates are usually slow. Thus, the utilization of photocatalysis has risen lately. Thus, the photocatalyst is activated with radiation, which brings about the separation of electrons and holes from, respectively, the valence and conduction bands of semiconductor photocatalysts, starting a series of chain reactions which leads to the generation of oxidants and, ultimately, to pollutant degradation.

However, even photocatalysis has limitations for future applications; for instance, the electrons and holes are usually recombined, long treatment times are required, etc. As a solution, the combination of photocatalysis with the application of an electrochemical field (photoelectrocatalysis) has been contemplated.

This Special Issue is focused on the application of photoelectrocatalysis for the treatment of different wastewaters. Thus, recent research focused on photoelectrocatalysis which somehow enhances previous studies for the degradation of pollutants and which contributes to the future application of this technology is welcome to form part of this Special Issue. For instance, the submission of manuscripts related to the synthesis of new photocatalysts which defeat the performance of the typical TiO₂, the set-up of new reactor configurations, the modification of the electrodes to ensure long and efficacious treatments, the evaluation of the process with real wastewaters, the scale-up of the process, etc. is encouraged.

Dr. Aida M. Diez
Dr. Vitor J. P. Vilar
Guest Editors

Manuscript Submission Information

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Keywords

Wastewater pollutant degradation
Photocatalysis coupled to electrolysis
Catalysts synthesis
Electrodes characterization
Advanced Oxidation Processes
Reactor set-up
Real applications

Published Papers (9 papers)

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Research

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15 pages, 4000 KiB

Open AccessArticle

Electro-Fenton-Based Technologies for Selectively Degrading Antibiotics in Aqueous Media

by Ángela Moratalla, Engracia Lacasa, Pablo Cañizares, Manuel A. Rodrigo and Cristina Sáez

Catalysts 2022, 12(6), 602; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12060602 - 31 May 2022

Cited by 4 | Viewed by 1655

Abstract

The viability of the Electro-Fenton (EF) process in the selective degradation of penicillin G (PenG) in complex solutions has been studied. The role of the anode material (boron-doped diamond (BDD) or mixed metal oxide (MMO)) and the cathode 3D support (foam or mesh), as well as the synergistic effect of UVC light irradiation (photoelectron-Fenton, PEF), have been evaluated. The results show that Pen G can be efficiently and selectively removed by EF, obtaining higher PenG removal rates when using the BDD anode (100%) than when using the MMO anode (75.5%). Additionally, mineralization is not favored under the experimental conditions tested (pH 3, 5 mA cm⁻²), since both aromatic and carboxylic acids accumulate in the reaction system as final products. In this regard, the EF-treated solution presents a high biological oxygen demand and a low percentage of Vibrio fischeri inhibition, which leads to high biodegradability and low toxicity of this final effluent. Furthermore, the combination with UVC radiation in the PEF process shows a clear synergistic effect on the degradation of penicillin G: 166.67% and 83.18% using MMO and BBD anodes, respectively. The specific energy required to attain the complete removal of PenG and high inhibition of the antibiotic effect is less than 0.05 Ah dm⁻³. This confirms that PEF can be efficiently used as a pretreatment of conventional wastewater treatment plants to decrease the chemical risk of complex solutions polluted with antibiotics. Full article

(This article belongs to the Special Issue Photo/Electrocatalysis for Wastewater Treatment)

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13 pages, 7890 KiB

Open AccessArticle

Inactivation of Escherichia coli Using Biogenic Silver Nanoparticles and Ultraviolet (UV) Radiation in Water Disinfection Processes

by Ljubica Tasic, Danijela Stanisic, Caio H. N. Barros, Letícia Khater Covesi and Erick R. Bandala

Catalysts 2022, 12(4), 430; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12040430 - 11 Apr 2022

Cited by 3 | Viewed by 2103

Abstract

This work tested the antimicrobial activity of three different biogenic silver nanoparticles (AgNPs) against Escherichia coli (E. coli) for water disinfection processes. The influence of different AgNP capping or stabilizing agents (e.g., protein or carbohydrate capped) and the use of ultraviolet (UV) radiation on the disinfection process were also assessed. The use of UV radiation was found to enhance the antimicrobial effects of AgNPs on E. coli. The antibacterial effects of AgNPs depended on the type of the capping biomolecules. Protein-capped nanoparticles showed greater antimicrobial effects compared with carbohydrate-capped (cellulose nanofibers, CNF) nanoparticles. Those capped with the fungal secretome proteins were the most active in E. coli inactivation. The least E. coli inactivation was observed for CNF-capped AgNPs. The size of the tested AgNPs also showed an expected effect on their anti-E. coli activity, with the smallest particles being the most active. The antimicrobial effects of biogenic AgNPs on E. coli make them an effective, innovative, and eco-friendly alternative for water disinfection processes, which supports further research into their use in developing sustainable water treatment processes. Full article

(This article belongs to the Special Issue Photo/Electrocatalysis for Wastewater Treatment)

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17 pages, 3466 KiB

Open AccessArticle

Evaluation of the Activation Procedure on Oxone Efficiency for Synthetic Olive Mill Wastewater Treatment

by Telma Vaz, Eva Domingues, João Gomes and Rui C. Martins

Catalysts 2022, 12(3), 291; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12030291 - 04 Mar 2022

Cited by 6 | Viewed by 2001

Abstract

Wastewater from the olive oil industry is an environmental problem which is growing in the Mediterranean region. Presence of phenolic compounds and high organic matter load are characteristics of this effluent that make it difficult to treat. In this study, the applicability of sulfate radical based advanced oxidation processes (SRbAOPs), using peroxymonosulfate (PMS) as oxidant, was evaluated in the treatment of synthetic olive mill wastewater (OMW). Different procedures for PMS activation were studied such as activation by Fe(II), radiation (visible and UV-A) and ultrasounds. The operation conditions were optimized by testing pH values, Fe(II) and PMS loads. At optimal conditions ([PMS] = 1600 mg/L, [Fe²⁺] = 700 mg/L and pH = 5) 60 ± 2% COD removal was achieved. This process shows to be selective since complete degradation of 3,4,5-trimetoxybenzoic acid was obtained after 3 min of reaction. The addition of light, PMS/LED/Fe(II) and PMS/UV-A/Fe(II), did not increase the efficiency of organic matter removal, with 56 ± 2% and 58 ± 1% of COD removal, respectively, comparatively to PMS/Fe(II) (60 ± 2%). PMS activated by ultrasounds led to 52 ± 3% and 23 ± 2% removal of phenolic compounds and COD, respectively, after 60 min. Toxicity tests using Lepidium sativum showed that treatment with PMS/UV-A led to a treated sample with mild inhibition of plant growth. Full article

(This article belongs to the Special Issue Photo/Electrocatalysis for Wastewater Treatment)

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12 pages, 2552 KiB

Open AccessFeature PaperArticle

Photocatalytic-Fenton Process under Simulated Solar Radiation Promoted by a Suitable Catalyst Selection

by Aida M. Díez, Helen E. Valencia, Maria Meledina, Joachim Mayer and Yury V. Kolen'ko

Catalysts 2021, 11(8), 885; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11080885 - 22 Jul 2021

Cited by 2 | Viewed by 2101

Abstract

Considering water scarcity, photo-based processes have been presented as a depollution technique, which should be optimized in order to be applied in the future. For that, the addition of an active photocatalyst and the usage of solar radiation are mandatory steps. Thus, Fe₃O₄–SiO₂–TiO₂ was synthesized, and its performance was evaluated using simulated solar radiation and methylene blue as a model pollutant. Under optimal conditions, 86% degradation was attained in 1 h. These results were compared to recent published data, and the better performance can be attributed to both the operational conditions selection and the higher photocatalyst activity. Indeed, Fe₃O₄–SiO₂–TiO₂ was physico-chemically characterized with techniques such as XRD, N₂ isotherms, spectrophotometry, FTIR, electrochemical assays and TEM. Full article

(This article belongs to the Special Issue Photo/Electrocatalysis for Wastewater Treatment)

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17 pages, 5569 KiB

Open AccessArticle

Green Synthesis of Flower-Shaped Copper Oxide and Nickel Oxide Nanoparticles via Capparis decidua Leaf Extract for Synergic Adsorption-Photocatalytic Degradation of Pesticides

by Amna Iqbal, Atta ul Haq, Gabriel Antonio Cerrón-Calle, Syed Ali Raza Naqvi, Paul Westerhoff and Sergi Garcia-Segura

Catalysts 2021, 11(7), 806; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11070806 - 30 Jun 2021

Cited by 43 | Viewed by 6827

Abstract

Green manufacturing of catalysts enables sustainable advanced oxidation processes and water treatment processes for removing trace contaminants such as pesticides. An environmentally friendly biosynthesis process produced high-surface-area CuO and NiO nanocatalysts using phytochemicals in the Capparis decidua leaf extract, which served as a reductant and influenced catalyst shape. Capparis decidua is a bushy shrub, widely distributed in dry and arid regions of Africa, Pakistan, India, Egypt, Jordan, Sudan, Saudi Arabia. The synthesized CuO and NiO nanoparticles were characterized by UV-vis spectroscopy (UV-vis), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) and thermo-gravimetric analysis/differential thermal analysis (TGA/DTA). The produced nanoparticles were spherical and flower-like in shape and have a characteristic face-centered cubic structure of CuO and NiO. Biosynthesized catalysts were photoactive and degraded recalcitrant pesticide Lambda-cyhalothrin (L-CHT). Photocatalytic degradation of L-CHT was affected by the initial L-CHT concentration, solution pH levels between 5 and 9, and photocatalyst concentration. The L-CHT removal percentage attained by CuO photocatalyst (~99%) was higher than for NiO photocatalyst (~89%). The degradation of L-CHT follows a pseudo-first-order kinetic model, and the apparent rate constant (k_app) decreased from 0.033 min⁻¹ for CuO to 0.0084 min⁻¹ for NiO photocatalyst. The novel flower-shaped nanoparticles demonstrated high stability in water and recyclability for removing L-CHT pesticide contamination in water. Full article

(This article belongs to the Special Issue Photo/Electrocatalysis for Wastewater Treatment)

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18 pages, 32481 KiB

Open AccessFeature PaperArticle

Turning Carbon Dioxide and Ethane into Ethanol by Solar-Driven Heterogeneous Photocatalysis over RuO₂- and NiO-co-Doped SrTiO₃

by Larissa O. Paulista, Josep Albero, Ramiro J. E. Martins, Rui A. R. Boaventura, Vítor J. P. Vilar, Tânia F. C. V. Silva and Hermenegildo García

Catalysts 2021, 11(4), 461; https://doi.org/10.3390/catal11040461 - 01 Apr 2021

Cited by 17 | Viewed by 3905

Abstract

The current work focused on the sunlight-driven thermo-photocatalytic reduction of carbon dioxide (CO₂), the primary greenhouse gas, by ethane (C₂H₆), the second most abundant element in shale gas, aiming at the generation of ethanol (EtOH), a renewable fuel. To promote this process, a hybrid catalyst was prepared and properly characterized, comprising of strontium titanate (SrTiO₃) co-doped with ruthenium oxide (RuO₂) and nickel oxide (NiO). The photocatalytic activity towards EtOH production was assessed in batch-mode and at gas-phase, under the influence of different conditions: (i) dopant loading; (ii) temperature; (iii) optical radiation wavelength; (vi) consecutive uses; and (v) electron scavenger addition. From the results here obtained, it was found that: (i) the functionalization of the SrTiO₃ with RuO₂ and NiO allows the visible light harvest and narrows the band gap energy (ca. 14–20%); (ii) the selectivity towards EtOH depends on the presence of Ni and irradiation; (iii) the catalyst photoresponse is mainly due to the visible photons; (iv) the photocatalyst loses > 50% efficiency right after the 2nd use; (v) the reaction mechanism is based on the photogenerated electron-hole pair charge separation; and (vi) a maximum yield of 64 μmol EtOH g_cat⁻¹ was obtained after 45-min (85 μmol EtOH g_cat⁻¹ h⁻¹) of simulated solar irradiation (1000 W m⁻²) at 200 °C, using 0.4 g L⁻¹ of SrTiO₃:RuO₂:NiO (0.8 wt.% Ru) with [CO₂]:[C₂H₆] and [Ru]:[Ni] molar ratios of 1:3 and 1:1, respectively. Notwithstanding, despite its exploratory nature, this study offers an alternative route to solar fuels’ synthesis from the underutilized C₂H₆ and CO₂. Full article

(This article belongs to the Special Issue Photo/Electrocatalysis for Wastewater Treatment)

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15 pages, 25529 KiB

Open AccessArticle

The Efficient Removal of Methylene Blue Dye Using CuO/PET Nanocomposite in Aqueous Solutions

by Suhad Abdulrahman Yasin, Samie Yaseen Sharaf Zeebaree, Aymn Yaseen Sharaf Zeebaree, Osama Ismail Haji Zebari and Ibtisam Abdulmajeed Saeed

Catalysts 2021, 11(2), 241; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11020241 - 11 Feb 2021

Cited by 22 | Viewed by 4031

Abstract

The present research investigates the application of the green method to produce nanocomposites. The CuO/PET fiber nanocomposite can be prepared in two ways. The first way involves the application of the electrospinning technique by which waste plastic cups of polyethylene terephthalate (PET) are converted into nanofibers. In the second way, the copper nanoparticle (CuONPs) is synthesized with the natural capped plant extract of sumac (Rhus Coriaria L., family Anacardiaceae) and the CuONPs are then combined as a filler with the PET nanofiber using a cross-linked solvent. The X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersion spectroscopy (EDS), and map elements distribution can be applied to investigate the surface modification and alteration of the composite nanofiber morphology. The collected data show that the produced CuO/PET nanocomposites have a high surface area, well distribution of elements, magnificent shape, and stable dispersion state. Furthermore, the CuO/PET nanocomposites are considered as an efficient photocatalytic removal of the toxic methylene blue dye (MB) in aqueous solutions. The results of the present study demonstrate that the photocatalytic efficiency for removing MB dye is achieved in a short time using a low-intensity irradiation ultraviolet light. Full article

(This article belongs to the Special Issue Photo/Electrocatalysis for Wastewater Treatment)

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Review

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31 pages, 2617 KiB

Open AccessFeature PaperReview

Heterogeneous Advanced Oxidation Processes: Current Approaches for Wastewater Treatment

by Gabriela Lama, Jessica Meijide, Angeles Sanromán and Marta Pazos

Catalysts 2022, 12(3), 344; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12030344 - 17 Mar 2022

Cited by 36 | Viewed by 4880

Abstract

Nowadays, water pollution is one of the most dangerous environmental problems in the world. The presence of the so-called emerging pollutants in the different water bodies, impossible to eliminate through conventional biological and physical treatments used in wastewater treatment plants due to their persistent and recalcitrant nature, means that pollution continues growing throughout the world. The presence of these emerging pollutants involves serious risks to human and animal health for aquatic and terrestrial organisms. Therefore, in recent years, advanced oxidation processes (AOPs) have been postulated as a viable, innovative and efficient technology for the elimination of these types of compounds from water bodies. The oxidation/reduction reactions triggered in most of these processes require a suitable catalyst. The most recent research focuses on the use and development of different types of heterogeneous catalysts, which are capable of overcoming some of the operational limitations of homogeneous processes such as the generation of metallic sludge, difficult separation of treated water and narrow working pH. This review details the current advances in the field of heterogeneous AOPs, Fenton processes and photocatalysts for the removal of different types of emerging pollutants. Full article

(This article belongs to the Special Issue Photo/Electrocatalysis for Wastewater Treatment)

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22 pages, 2847 KiB

Open AccessReview

The Influence of Photocatalytic Reactors Design and Operating Parameters on the Wastewater Organic Pollutants Removal—A Mini-Review

by Alexandru Enesca

Catalysts 2021, 11(5), 556; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11050556 - 27 Apr 2021

Cited by 36 | Viewed by 4616

Abstract

The organic pollutants removal by conventional methods (adsorption, coagulation, filtration, microorganism and enzymes) showed important limitation due to the reluctance of these molecules. An alternative to this issue is represented by the photocatalytic technology considered as an advanced oxidation process (AOP). The photoreactors design and concepts vary based on the working regime (static or dynamic), photocatalyst morphology (powders or bulk) and volume. This mini-review aims to provide specific guidelines on the correlations between the photoreactor concept characteristics (working regime, volume and flow rate), irradiation scenarios (light spectra, irradiation period and intensity) and the photocatalytic process parameters (photocatalyst materials and dosage, pollutant type and concentration, pollutant removal efficiency and constant rate). The paper considers two main photoreactor geometries (cylindrical and rectangular) and analyses the influence of parameters optimization on the overall photocatalytic efficiency. Based on the systematic evaluation of the input data reported in the scientific papers, several perspectives regarding the photocatalytic reactors’ optimization were included. Full article

(This article belongs to the Special Issue Photo/Electrocatalysis for Wastewater Treatment)

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