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Photo-Fenton Process in Water Treatment

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Green Chemistry".

Deadline for manuscript submissions: closed (31 August 2023) | Viewed by 13662

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Prof. Dr. M. Gilles Mailhot

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Institut de Chimie de Clermont-Ferrand, Université Clermont Auvergne—CNRS, F-63000 Clermont-Ferrand, France
Interests: environmental chemistry; water treatment; atmospheric chemistry; solar technologies; micropollutants removal
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Prof. Dr. José Antonio Sánchez Pérez

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1. Centre (CIESOL), Joint Centre University of Almería—CIEMAT, Ctra. Sacramento s/n, 04120 Almería, Spain
2. Chemical Engineering Department, University of Almería, Ctra. Sacramento s/n, 04120 Almería, Spain
Interests: environmental chemical engineering; solar photocatalysis; advanced oxidation processes; contaminants of emerging concern; wastewater treatment
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Dear Colleagues,

The degradation of water resource quality, mainly due to organic compounds from human activities, requires increasingly advanced treatments. Among the most studied and successful treatments are the advanced oxidation processes (AOPs), of which the (photo-)Fenton process occupies an important place in terms of development and efficiency. It has been reported to be effective for the removal of many families of contaminants, such as pesticides, pharmaceuticals, benzene and phenol derivatives, dyes, PCBs and so on. However, due to some drawbacks of the Fenton process, many modifications of the process have been and are still being proposed in order enable the use of this process in natural environments. Among them, the addition of iron-complexing agents or the synthesis of new composites including iron species have shown promising results for the effectiveness of the Fenton process at neutral pH.

All researchers working in the field are cordially invited to contribute original research papers or reviews to this Special Issue of Molecules, which will report on the use of Fenton or photo-Fenton processes in water treatment.

Prof. Dr. M. Gilles Mailhot
Prof. Dr. José Antonio Sánchez Pérez
Guest Editors

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Keywords

photochemistry
(photo)catalysis
nanocomposites
complexing agents
iron
degradation
pollutants

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Published Papers (6 papers)

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Research

16 pages, 2578 KiB

Open AccessArticle

Possibilities and Limitations of the Sono-Fenton Process Using Mid-High-Frequency Ultrasound for the Degradation of Organic Pollutants

by Efraím A. Serna-Galvis, Javier Silva-Agredo, Judy Lee, Adriana Echavarría-Isaza and Ricardo A. Torres-Palma

Molecules 2023, 28(3), 1113; https://doi.org/10.3390/molecules28031113 - 22 Jan 2023

Cited by 9 | Viewed by 2230

Abstract

Mid-high-frequency ultrasound (200–1000 kHz) eliminates organic pollutants and also generates H₂O₂. To take advantage of H₂O₂, iron species can be added, generating a hybrid sono-Fenton process (sF). This paper presents the possibilities and limitations of sF. Heterogeneous (a natural mineral) and homogeneous (Fe²⁺ and Fe³⁺ ions) iron sources were considered. Acetaminophen, ciprofloxacin, and methyl orange were the target organic pollutants. Ultrasound alone induced the pollutants degradation, and the dual competing role of the natural mineral (0.02–0.20 g L⁻¹) meant that it had no significant effects on the elimination of pollutants. In contrast, both Fe²⁺ and Fe³⁺ ions enhanced the pollutants’ degradation, and the elimination using Fe²⁺ was better because of its higher reactivity toward H₂O₂. However, the enhancement decreased at high Fe²⁺ concentrations (e.g., 5 mg L⁻¹) because of scavenger effects. The Fe²⁺ addition significantly accelerated the elimination of acetaminophen and methyl orange. For ciprofloxacin, at short treatment times, the degradation was enhanced, but the pollutant complexation with Fe³⁺ that came from the Fenton reaction caused degradation to stop. Additionally, sF did not decrease the antimicrobial activity associated with ciprofloxacin, whereas ultrasound alone did. Therefore, the chemical structure of the pollutant plays a crucial role in the feasibility of the sF process. Full article

(This article belongs to the Special Issue Photo-Fenton Process in Water Treatment)

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14 pages, 5922 KiB

Open AccessArticle

Use of Fluorescence Spectroscopy and Chemometrics to Visualise Fluoroquinolones Photodegradation Major Trends: A Confirmation Study with Mass Spectrometry

by Iván Sciscenko, Paula García-Negueroles, Ana María Amat, Isabel Oller, Carlos Escudero-Oñate, Laura Ferrando-Climent and Antonio Arques

Molecules 2023, 28(2), 777; https://doi.org/10.3390/molecules28020777 - 12 Jan 2023

Cited by 3 | Viewed by 1884

Abstract

In this work, we employed EEM-PARAFAC (fluorescence excitation-emission matrices-parallel factor analysis) as a low-cost tool to study the oxidation pathways of (fluoro)quinolones. Amounts of 12.5 μM of enrofloxacin (ENR), ciprofloxacin (CIP), ofloxacin (OFL), oxolinic acid (OA), and flumequine (FLU), as individual solutions, were irradiated under UVA light. A 5-component PARAFAC model was obtained, four of them related to the parent pollutants, named as ENR-like (including CIP), OFL-like, OA-like, and FLU-like, and an additional one related to photoproducts, called ENRox-like (with an emission red-shift with respect to the ENR-like component). Mass spectrometry was employed to correlate the five PARAFAC components with their plausible molecular structures. Results indicated that photoproducts presenting: (i) hydroxylation or alkyl cleavages exhibited fingerprints analogous to those of the parent pollutants; (ii) defluorination and hydroxylation emitted within the ENRox-like region; (iii) the aforementioned changes plus piperazine ring cleavage emitted within the OA-like region. Afterwards, the five antibiotics were mixed in a single solution (each at a concentration of 0.25 μM) in seawater, PARAFAC being also able to deconvolute the fingerprint of humic-like substances. This approach could be a potential game changer in the analysis of (fluorescent) contaminants of emerging concern removals in complex matrices, giving rapid visual insights into the degradation pathways. Full article

(This article belongs to the Special Issue Photo-Fenton Process in Water Treatment)

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13 pages, 2394 KiB

Open AccessArticle

Molecular Oxygen Activation by Citric Acid Boosted Pyrite–Photo–Fenton Process for Degradation of PPCPs in Water

by Juntao Guo, Yihui Zhang, Jinjun Li, Feng Wu and Liting Luo

Molecules 2023, 28(2), 607; https://doi.org/10.3390/molecules28020607 - 6 Jan 2023

Cited by 5 | Viewed by 1875

Abstract

Pyrite has been used in photo-Fenton reactions for the degradation of pollutants, but the application of photo-Fenton processes with extra H₂O₂ in real water/wastewater treatment has still been limited by the economic cost of H₂O₂ and artificial light sources. Herein, citric acid (CA) and simulated/natural sunlight are used to develop a pyrite-based photo-Fenton system (pyrite–CA–light) in situ generating H₂O₂ through the enhanced activation of molecular oxygen. The degradation of pharmaceuticals and personal care products (PPCPs), especially acetaminophen (APAP) as the main target pollutant, in the pyrite–CA–light system was investigated. The effects of influencing factors such as various organic acids, APAP concentration, pH, pyrite dosage, CA concentration and co-existing anions (HCO₃⁻, Cl⁻, NO₃⁻, SO₄²⁻ and H₂PO₄⁻) were examined. At a pyrite dosage of 0.1 g L⁻¹, CA concentration of 0.6 mM and an initial pH of 6.0, the degradation efficiency of APAP (30 μM) was 99.1% within 30 min under the irradiation of xenon lamp (70 W, λ ≥ 350 nm). Almost the same high efficiency of APAP degradation (93.9%) in the system was achieved under natural sunlight irradiation (ca. 650 W m⁻²). The scavenging experiments revealed that the dominant active species for degrading APAP was hydroxyl radical (HO^•). Moreover, a quantitative structural–activity relationship (QSAR) model for pseudo-first-order rate constants (k_obs) was established with a high significance (R² = 0.932, p = 0.001) by using three descriptors: octanol–water partition coefficient (logKow), dissociation constant (pK_a) and highest occupied molecular orbital (HOMO). This work provides an innovative strategy of the photo-Fenton process for the degradation of PPCPs using natural minerals and ordinary carboxylic acid under sunlight. Full article

(This article belongs to the Special Issue Photo-Fenton Process in Water Treatment)

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14 pages, 3057 KiB

Open AccessArticle

Effect of Iron Complex Source on MWWTP Effluent Treatment by Solar Photo-Fenton: Micropollutant Degradation, Toxicity Removal and Operating Costs

by Eduardo O. Marson, Ivo A. Ricardo, Cleiseano E. S. Paniagua, Serena M. Malta, Carlos Ueira-Vieira, Maria Clara V. M. Starling, José Antonio Sánchez Pérez and Alam G. Trovó

Molecules 2022, 27(17), 5521; https://doi.org/10.3390/molecules27175521 - 27 Aug 2022

Cited by 4 | Viewed by 1777

Abstract

Benzophenone-3, fipronil and propylparaben are micropollutants that are potential threats to ecosystems and have been detected in aquatic environments. However, studies involving the investigation of new technologies aiming at their elimination from these matrices, such as advanced oxidation processes, remain scarce. In this study, different iron complexes (FeCit, FeEDTA, FeEDDS and FeNTA) were evaluated for the degradation of a mixture of these micropollutants (100 µg L⁻¹ each) spiked in municipal wastewater treatment plant (MWWTP) effluent at pH 6.9 by solar photo-Fenton. Operational parameters (iron and H₂O₂ concentration and Fe/L molar ratio) were optimized for each complex. Degradation efficiencies improved significantly by increasing the concentration of iron complexes (1:1 Fe/L) from 12.5 to 100 µmol L⁻¹ for FeEDDS, FeEDTA and FeNTA. The maximum degradation reached with FeCit for all iron concentrations was limited to 30%. Different Fe/L molar ratios were required to maximize the degradation efficiency for each ligand: 1:1 for FeNTA and FeEDTA, 1:3 for FeEDDS and 1:5 for FeCit. Considering the best Fe/L molar ratios, higher degradation rates were reached using 5.9 mmol L⁻¹ H₂O₂ for FeNTA and FeEDTA compared to 1.5 and 2.9 mmol L⁻¹ H₂O₂ for FeEDDS and FeCit, respectively. Acute toxicity to Canton S. strain D. melanogaster flies reduced significantly after treatment for all iron complexes, indicating the formation of low-toxicity by-products. FeNTA was considered the best iron complex source in terms of the kinetic constant (0.10 > 0.063 > 0.051 > 0.036 min⁻¹ for FeCit, FeNTA, FeEDTA and FeEDDS, respectively), organic carbon input and cost-benefit (USD 327 m⁻³ > USD 20 m⁻³ > USD 16 m⁻³ > USD 13 m⁻³ for FeEDDS, FeCit, FeEDTA and FeNTA, respectively) when compared to the other tested complexes. Full article

(This article belongs to the Special Issue Photo-Fenton Process in Water Treatment)

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11 pages, 1455 KiB

Open AccessArticle

Miniaturized Method for Chemical Oxygen Demand Determination Using the PhotoMetrix PRO Application

by Lisandro von Mühlen, Osmar D. Prestes, Marco F. Ferrão and Carla Sirtori

Molecules 2022, 27(15), 4721; https://doi.org/10.3390/molecules27154721 - 23 Jul 2022

Cited by 6 | Viewed by 2580

Abstract

The analysis of chemical oxygen demand (COD) plays an important role in measuring water pollution, but it normally has a high ecological price. Advances in image acquisition and processing techniques enable the use of mobile devices for analytical purposes. Here, the PhotoMetrix PRO application was used for image acquisition and multivariate analysis. Statistical analysis showed no significant difference in the results compared to the standard method, with no adverse effect of the volume reduction. The cost of analysis and waste generation were reduced by one third, while the analysis time was reduced by one fifth. The miniaturized method was successfully employed in the analysis of several matrices and for the evaluation of advanced oxidation processes. The AGREE score was improved by 25% due to miniaturization. For these reasons, the miniaturized PhotoMetrix PRO method is a suitable option for COD analysis, being less hazardous to the environment due to reductions in the chemicals used and in waste generation. Full article

(This article belongs to the Special Issue Photo-Fenton Process in Water Treatment)

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17 pages, 2236 KiB

Open AccessArticle

Comparative Effect of UV, UV/H₂O₂ and UV/H₂O₂/Fe on Terbuthylazine Degradation in Natural and Ultrapure Water

by José Antonio Andrades, Manuel Lojo-López, Agata Egea-Corbacho and José María Quiroga

Molecules 2022, 27(14), 4507; https://doi.org/10.3390/molecules27144507 - 14 Jul 2022

Cited by 8 | Viewed by 2128

Abstract

Different advanced oxidation processes (AOPs) (ultraviolet radiation, hydrogen peroxide photolysis and photo-Fenton) were applied to test the degradation of terbuthylazine in three types of water: (a) ultrapure water, (b) surface water from the Gaditana area (Los Hurones reservoir, Cádiz, Spain) and (c) groundwater from the Tempul spring in Jerez de la Frontera (Cádiz, Spain). The experiments were carried out on a laboratory scale, using two different types of reactors, batch and semi-continuous. In batch reactors, the most efficient process for the experiments carried out with both ultrapure water and underground groundwater was ultraviolet radiation, whereas for surface water from the Gaditana area, the process that obtained the best results was the photolysis of hydrogen peroxide with 2.5 mg L⁻¹ of H₂O₂. In semi-continuous reactors, the most efficient process was the photolysis of hydrogen peroxide with 2.5 mg L⁻¹ of H₂O₂ for all the matrices studied. In both types of reactors, terbuthylazine degradation percentages higher than 90% were achieved; the main difference was in the reaction time, which varied from minutes in the batch reactor to seconds in the semi-continuous reactor. In all the applied AOPs, N-terbutyl-6-hydroxy-N′ethyl-1,3,5-triazine-2,4-diamine (TBA-212) was generated as a reaction intermediate. Full article

(This article belongs to the Special Issue Photo-Fenton Process in Water Treatment)

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