Materials and Processes for Photocatalytic and (Photo)Electrocatalytic Removal of Bio-Refractory Pollutants and Emerging Contaminants from Waters

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

Deadline for manuscript submissions: closed (15 August 2021) | Viewed by 30425

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Dipartimento di Ingegneria Meccanica, Chimica e dei Materiali, Università di Cagliari, Piazza D'armi, 09123 Cagliari, Italy
Interests: synthesis and characterization of materials for electrochemical and photoelectrochemical processes; electrocatalysis for wastewater treatment and energy production; electrochemical water treatment; functionalization of electrode materials with conducting polymers
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Water pollution from biorefractory pollutants and emerging contaminants is still a very topical worldwide problem. Examples of these pollutants include disinfection by-products, pharmaceutical and personal care products, persistent organic chemicals, as well as their degradation products. The occurrence of these contaminants in waters has raised increasing concern due to their accumulation and persistence in the environment and the threat to the ecological system and human health. Conventional water treatment processes are known to be generally inadequate for the elimination of these persistent contaminants. Thus, impressive efforts of the scientific community have been addressed to the development and characterization of materials and processes able to efficiently oxidize these compounds. Among the so-called advanced oxidation processes, the electrochemical and photoelectrochemical processes present such advantages as versatility, high energy efficiency, amenability of automation, and mild operating conditions with limited use of chemicals.

Therefore, this Special Issue focuses on the advancements on materials and processes for electro- and photoelectrochemical removal of biorefractory pollutants and emerging contaminants from waters. Therefore, synthesis, characterization, and application of materials as electrodes and photoelectrodes for the oxidation of contaminants, as well as the studies of catalytic processes, reaction kinetics, and modelling/simulation of reactions and processes are very welcome.

Prof. Dr. Annalisa Vacca
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • electrochemical oxidation
  • photoelectrocatalytic degradation
  • synthesis and characterization of electrodes
  • preparation and application of photoanodes
  • emerging contaminants
  • biorefractory pollutants

Published Papers (10 papers)

Order results
Result details
Select all
Export citation of selected articles as:

Editorial

Jump to: Research

2 pages, 157 KiB  
Editorial
Materials and Processes for Photocatalytic and (Photo)Electrocatalytic Removal of Bio-Refractory Pollutants and Emerging Contaminants from Waters
by Annalisa Vacca
Catalysts 2021, 11(6), 666; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11060666 - 24 May 2021
Viewed by 1324
Abstract
This volume is focused on materials and processes for the electro- and photoelectrochemical removal of biorefractory pollutants and emerging contaminants from waters to show the importance of electrochemistry and photoelectrochemistry in offering solutions to current environmental problems [...] Full article

Research

Jump to: Editorial

21 pages, 4654 KiB  
Article
Simulated Ageing of Crude Oil and Advanced Oxidation Processes for Water Remediation since Crude Oil Pollution
by Filomena Lelario, Giuliana Bianco, Sabino Aurelio Bufo and Laura Scrano
Catalysts 2021, 11(8), 954; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11080954 - 10 Aug 2021
Cited by 1 | Viewed by 1676
Abstract
Crude oil can undergo biotic and abiotic transformation processes in the environment. This article deals with the fate of an Italian crude oil under simulated solar irradiation to understand (i) the modification induced on its composition by artificial ageing and (ii) the transformations [...] Read more.
Crude oil can undergo biotic and abiotic transformation processes in the environment. This article deals with the fate of an Italian crude oil under simulated solar irradiation to understand (i) the modification induced on its composition by artificial ageing and (ii) the transformations arising from different advanced oxidation processes (AOPs) applied as oil-polluted water remediation methods. The AOPs adopted were photocatalysis, sonolysis and, simultaneously, photocatalysis and sonolysis (sonophotocatalysis). Crude oil and its water-soluble fractions underwent analysis using GC-MS, liquid-state 1H-NMR, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), and fluorescence. The crude oil after light irradiation showed (i) significant modifications induced by the artificial ageing on its composition and (ii) the formation of potentially toxic substances. The treatment produced oil oxidation with a particular effect of double bonds oxygenation. Non-polar compounds present in the water-soluble oil fraction showed a strong presence of branched alkanes and a good amount of linear and aromatic alkanes. All remediation methods utilised generated an increase of C5 class and a decrease of C6–C9 types of compounds. The analysis of polar molecules elucidated that oxygenated compounds underwent a slight reduction after photocatalysis and a sharp decline after sonophotocatalytic degradation. Significant modifications did not occur by sonolysis. Full article
Show Figures

Figure 1

15 pages, 5055 KiB  
Article
Analysis of Photocatalytic Degradation of Phenol with Exfoliated Graphitic Carbon Nitride and Light-Emitting Diodes Using Response Surface Methodology
by Adeem Ghaffar Rana and Mirjana Minceva
Catalysts 2021, 11(8), 898; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11080898 - 25 Jul 2021
Cited by 17 | Viewed by 3381
Abstract
Response surface methodology (RSM) involving a Box–Benkhen design (BBD) was employed to analyze the photocatalytic degradation of phenol using exfoliated graphitic carbon nitride (g-C3N4) and light-emitting diodes (wavelength = 430 nm). The interaction between three parameters, namely, catalyst concentration [...] Read more.
Response surface methodology (RSM) involving a Box–Benkhen design (BBD) was employed to analyze the photocatalytic degradation of phenol using exfoliated graphitic carbon nitride (g-C3N4) and light-emitting diodes (wavelength = 430 nm). The interaction between three parameters, namely, catalyst concentration (0.25–0.75 g/L), pollutant concentration (20–100 ppm), and pH of the solution (3–10), was examined and modeled. An empirical regression quadratic model was developed to relate the phenol degradation efficiency with these three parameters. Analysis of variance (ANOVA) was then applied to examine the significance of the model; this showed that the model is significant with an insignificant lack of fit and an R2 of 0.96. The statistical analysis demonstrated that, in the studied range, phenol concentration considerably affected phenol degradation. The RSM model shows a significant correlation between predicted and experimental values of photocatalytic degradation of phenol. The model’s accuracy was tested for 50 ppm of phenol under optimal conditions involving a catalyst concentration of 0.4 g/L catalysts and a solution pH of 6.5. The model predicted a degradation efficiency of 88.62%, whereas the experimentally achieved efficiency was 83.75%. Full article
Show Figures

Graphical abstract

12 pages, 1882 KiB  
Article
Effect of Potential and Chlorides on Photoelectrochemical Removal of Diethyl Phthalate from Water
by Laura Mais, Simonetta Palmas, Michele Mascia and Annalisa Vacca
Catalysts 2021, 11(8), 882; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11080882 - 22 Jul 2021
Cited by 7 | Viewed by 1868
Abstract
Removal of persistent pollutants from water by photoelectrocatalysis has emerged as a promising powerful process. Applied potential plays a key role in the photocatalytic activity of the semi-conductor as well as the possible presence of chloride ions in the solution. This work aims [...] Read more.
Removal of persistent pollutants from water by photoelectrocatalysis has emerged as a promising powerful process. Applied potential plays a key role in the photocatalytic activity of the semi-conductor as well as the possible presence of chloride ions in the solution. This work aims to investigate these effects on the photoelectrocatalytic oxidation of diethyl phthalate (DEP) by using TiO2 nanotubular anodes under solar light irradiation. PEC tests were performed at constant potentials under different concentration of NaCl. The process is able to remove DEP following a pseudo-first order kinetics: values of kapp of 1.25 × 10−3 min−1 and 1.56 × 10−4 min−1 have been obtained at applied potentials of 1.8 and 0.2 V, respectively. Results showed that, depending on the applied potential, the presence of chloride ions in the solution affects the degradation rate resulting in a negative effect: the presence of 500 mM of Cl reduces the value of kapp by 50 and 80% at 0.2 and 1.8 V respectively. Full article
Show Figures

Figure 1

14 pages, 4567 KiB  
Article
Visible Light Responsive Strontium Carbonate Catalyst Derived from Solvothermal Synthesis
by Pornnaphat Wichannananon, Thawanrat Kobkeatthawin and Siwaporn Meejoo Smith
Catalysts 2020, 10(9), 1069; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10091069 - 17 Sep 2020
Cited by 12 | Viewed by 2729
Abstract
A single crystalline phase of strontium carbonate (SrCO3) was successfully obtained from solvothermal treatments of hydrated strontium hydroxide in ethanol (EtOH) at 100 °C for 2 h, using specific Sr:EtOH mole ratios of 1:18 or 1:23. Other solvothermal treatment times (0.5, [...] Read more.
A single crystalline phase of strontium carbonate (SrCO3) was successfully obtained from solvothermal treatments of hydrated strontium hydroxide in ethanol (EtOH) at 100 °C for 2 h, using specific Sr:EtOH mole ratios of 1:18 or 1:23. Other solvothermal treatment times (0.5, 1.0 and 3 h), temperatures (80 and 150 °C) and different Sr:EtOH mole ratios (1:13 and 1:27) led to formation of mixed phases of Sr-containing products, SrCO3 and Sr(OH)2 xH2O. The obtained products (denoted as 1:18 SrCO3 and 1:23 SrCO3), containing a single phase of SrCO3, were further characterized in comparison with commercial SrCO3, and each SrCO3 material was employed as a photocatalyst for the degradation of methylene blue (MB) in water under visible light irradiation. Only the 1:23 SrCO3 sample is visible light responsive (Eg = 2.62 eV), possibly due to the presence of ethanol in the structure, as detected by thermogravimetric analysis. On the other hand, the band gap of 1:18 SrCO3 and commercial SrCO3 are 4.63 and 3.25 eV, respectively, and both samples are UV responsive. The highest decolourisation efficiency of MB solutions was achieved using the 1:23 SrCO3 catalyst, likely due to its narrow bandgap. The variation in colour removal results in the dark and under visible light irradiation, with radical scavenging tests, suggests that the high decolourisation efficiency was mainly due to a generated hydroxyl-radical-related reaction pathway. Possible degradation products from MB oxidation under visible light illumination in the presence of SrCO3 are aromatic sulfonic acids, dimethylamine and phenol, as implied by MS direct injection measurements. Key findings from this work could give more insight into alternative synthesis routes to tailor the bandgap of SrCO3 materials and possible further development of cocatalysts and composites for environmental applications. Full article
Show Figures

Graphical abstract

14 pages, 2424 KiB  
Article
On the Role of the Cathode for the Electro-Oxidation of Perfluorooctanoic Acid
by Alicia L. Garcia-Costa, Andre Savall, Juan A. Zazo, Jose A. Casas and Karine Groenen Serrano
Catalysts 2020, 10(8), 902; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10080902 - 08 Aug 2020
Cited by 15 | Viewed by 3382
Abstract
Perfluorooctanoic acid (PFOA), C7F15COOH, has been widely employed over the past fifty years, causing an environmental problem because of its dispersion and low biodegradability. Furthermore, the high stability of this molecule, conferred by the high strength of the C-F [...] Read more.
Perfluorooctanoic acid (PFOA), C7F15COOH, has been widely employed over the past fifty years, causing an environmental problem because of its dispersion and low biodegradability. Furthermore, the high stability of this molecule, conferred by the high strength of the C-F bond makes it very difficult to remove. In this work, electrochemical techniques are applied for PFOA degradation in order to study the influence of the cathode on defluorination. For this purpose, boron-doped diamond (BDD), Pt, Zr, and stainless steel have been tested as cathodes working with BDD anode at low electrolyte concentration (3.5 mM) to degrade PFOA at 100 mg/L. Among these cathodic materials, Pt improves the defluorination reaction. The electro-degradation of a PFOA molecule starts by a direct exchange of one electron at the anode and then follows a complex mechanism involving reaction with hydroxyl radicals and adsorbed hydrogen on the cathode. It is assumed that Pt acts as an electrocatalyst, enhancing PFOA defluorination by the reduction reaction of perfluorinated carbonyl intermediates on the cathode. The defluorinated intermediates are then more easily oxidized by HO radicals. Hence, high mineralization (xTOC: 76.1%) and defluorination degrees (xF: 58.6%) were reached with Pt working at current density j = 7.9 mA/cm2. This BDD-Pt system reaches a higher efficiency in terms of defluorination for a given electrical charge than previous works reported in literature. Influence of the electrolyte composition and initial pH are also explored. Full article
Show Figures

Graphical abstract

16 pages, 2555 KiB  
Article
Fast Microwave Synthesis of Gold-Doped TiO2 Assisted by Modified Cyclodextrins for Photocatalytic Degradation of Dye and Hydrogen Production
by Cécile Machut, Nicolas Kania, Bastien Léger, Frédéric Wyrwalski, Sébastien Noël, Ahmed Addad, Eric Monflier and Anne Ponchel
Catalysts 2020, 10(7), 801; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10070801 - 18 Jul 2020
Cited by 10 | Viewed by 3207
Abstract
A convenient and fast microwave synthesis of gold-doped titanium dioxide materials was developed with the aid of commercially available and common cyclodextrin derivatives, acting both as reducing and stabilizing agents. Anatase titanium oxide was synthesized from titanium chloride by microwave heating without calcination. [...] Read more.
A convenient and fast microwave synthesis of gold-doped titanium dioxide materials was developed with the aid of commercially available and common cyclodextrin derivatives, acting both as reducing and stabilizing agents. Anatase titanium oxide was synthesized from titanium chloride by microwave heating without calcination. Then, the resulting titanium oxide was decorated by gold nanoparticles thanks to a microwave-assisted reduction of HAuCl4 by cyclodextrin in alkaline conditions. The materials were fully characterized by UV-Vis spectroscopy, X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and N2 adsorption-desorption measurements, while the metal content was determined by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The efficiency of the TiO2@Au materials was evaluated with respect to two different photocatalytic reactions, such as dye degradation and hydrogen evolution from water. Full article
Show Figures

Graphical abstract

21 pages, 6513 KiB  
Article
Photocatalytic Degradation of Chlorpyrifos with Mn-WO3/SnS2 Heterostructure
by Charlie M. Kgoetlana, Soraya P. Malinga and Langelihle N. Dlamini
Catalysts 2020, 10(6), 699; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10060699 - 21 Jun 2020
Cited by 26 | Viewed by 3603
Abstract
Tungsten trioxide (WO3) is a photocatalyst that has gained interest amongst researchers because of its non-toxicity, narrow band gap and superior charge transport. Due to its fast charge recombination, modification is vital to counteract this limitation. In this paper, we report [...] Read more.
Tungsten trioxide (WO3) is a photocatalyst that has gained interest amongst researchers because of its non-toxicity, narrow band gap and superior charge transport. Due to its fast charge recombination, modification is vital to counteract this limitation. In this paper, we report on the fabrication of Mn-doped WO3/SnS2 nanoparticles, which were synthesised with the aim of minimising the recombination rates of the photogenerated species. The nanomaterials were characterised using spectroscopic techniques (UV-Vis-diffuse reflectance spectroscopy (DRS), Raman, XRD, photoluminescence (PL) and electrochemical impedance spectroscopy (EIS)) together with microscopic techniques (FESEM-EDS and high resolution transmission electron microscopy selected area electron diffraction (HRTEM-SAED)) to confirm the successful formation of Mn-WO3/SnS2 nanoparticles. The Mn-doped WO3/SnS2 composite was a mixture of monoclinic and hexagonal phases, confirmed by XRD and Raman analysis. The Mn-WO3/SnS2 heterojunction showed enhanced optical properties compared to those of the un-doped WO3/SnS2 nanoparticles, which confirms the successful charge separation. The Brunauer–Emmett–Teller (BET) analysis indicated that the nanoparticles were mesoporous as they exhibited a Type IV isotherm. These nanomaterials appeared as a mixture of rectangular rods and sheet-like shapes with an increased surface area (77.14 m2/g) and pore volume (0.0641 cm3/g). The electrochemical measurements indicated a high current density (0.030 mA/cm2) and low charge transfer resistance (157.16 Ω) of the Mn-WO3/SnS2 heterojunction, which infers a high charge separation, also complemented by photoluminescence with low emission peak intensity. The Mott–Schottky (M-S) plot indicated a positive slope characteristic of an nn heterojunction semiconductor, indicating that electrons are the major charge carriers. Thus, the efficiency of Mn-WO3/SnS2 heterojunction photocatalyst was monitored for the degradation of chlorpyrifos. The effects of pH (3–9), catalyst loading (0.1–2 g) and initial chlorpyrifos concentration (100 ppb–20 ppm) were studied. It was observed that the degradation was purely due to photocatalysis, as no loss of chlorpyrifos was observed within 30 min in the dark. Chlorpyrifos removal using Mn-WO3/SnS2 was performed at the optimum conditions of pH = 7, catalyst loading = 1 g and chlorpyrifos concentration = 1000 ppb in 90 min. The complete degradation of chlorpyrifos and its major degradation by-product 3,5,6-trichloropyridin-2-ol (TCP) was achieved. Kinetic studies deduced a second order reaction at 209 × 10−3 M−1s−1. Full article
Show Figures

Figure 1

17 pages, 2277 KiB  
Article
TiO2 and Active Coated Glass Photodegradation of Ibuprofen
by Samer Khalaf, Jawad H. Shoqeir, Filomena Lelario, Sabino A. Bufo, Rafik Karaman and Laura Scrano
Catalysts 2020, 10(5), 560; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10050560 - 18 May 2020
Cited by 22 | Viewed by 3751
Abstract
Commercial non-steroidal anti-inflammatory drugs (NSAIDs) are considered as toxic to the environment since they induce side effects when consumed by humans or aquatic life. Ibuprofen is a member of the NSAID family and is widely used as an anti-inflammatory and painkiller agent. Photolysis [...] Read more.
Commercial non-steroidal anti-inflammatory drugs (NSAIDs) are considered as toxic to the environment since they induce side effects when consumed by humans or aquatic life. Ibuprofen is a member of the NSAID family and is widely used as an anti-inflammatory and painkiller agent. Photolysis is a potentially important method of degradation for several emerging contaminants, and individual compounds can undergo photolysis to various degrees, depending on their chemical structure. The efficiency oftitanium dioxide (TiO2) and photocatalysis was investigated for the removal of ibuprofen from the aquatic environment, and the performance of these different processes was evaluated. In heterogeneous photocatalysis, two experiments were carried out using TiO2 as (i) dispersed powder, and (ii) TiO2 immobilized on the active surface of commercial coated glass. The kinetics of each photoreaction was determined, and the identification of the photoproducts was carried out by liquid chromatography coupled with Fourier-transform ion cyclotron resonance mass spectrometry (LC-FTICR MS). The overall results suggest that the TiO2 active thin layer immobilized on the glass substrate can avoid recovery problems related to the use of TiO2 powder in heterogeneous photocatalysis and may be a promising tool toward protecting the environment from emerging contaminants such as ibuprofen and its derivatives. Full article
Show Figures

Figure 1

20 pages, 4914 KiB  
Article
Enhanced Photocatalytic Activity of Au/TiO2 Nanoparticles against Ciprofloxacin
by Pedro Martins, Sandro Kappert, Hoai Nga Le, Victor Sebastian, Klaus Kühn, Madalena Alves, Luciana Pereira, Gianaurelio Cuniberti, Manuel Melle-Franco and Senentxu Lanceros-Méndez
Catalysts 2020, 10(2), 234; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10020234 - 15 Feb 2020
Cited by 47 | Viewed by 5115
Abstract
In the last decades, photocatalysis has arisen as a solution to degrade emerging pollutants such as antibiotics. However, the reduced photoactivation of TiO2 under visible radiation constitutes a major drawback because 95% of sunlight radiation is not being used in this process. [...] Read more.
In the last decades, photocatalysis has arisen as a solution to degrade emerging pollutants such as antibiotics. However, the reduced photoactivation of TiO2 under visible radiation constitutes a major drawback because 95% of sunlight radiation is not being used in this process. Thus, it is critical to modify TiO2 nanoparticles to improve the ability to absorb visible radiation from sunlight. This work reports on the synthesis of TiO2 nanoparticles decorated with gold (Au) nanoparticles by deposition-precipitation method for enhanced photocatalytic activity. The produced nanocomposites absorb 40% to 55% more radiation in the visible range than pristine TiO2, the best results being obtained for the synthesis performed at 25 °C and with Au loading of 0.05 to 0.1 wt. %. Experimental tests yielded a higher photocatalytic degradation of 91% and 49% of ciprofloxacin (5 mg/L) under UV and visible radiation, correspondingly. Computational modeling supports the experimental results, showing the ability of Au to bind TiO2 anatase surfaces, the relevant role of Au transferring electrons, and the high affinity of ciprofloxacin to both Au and TiO2 surfaces. Hence, the present work represents a reliable approach to produce efficient photocatalytic materials and an overall contribution in the development of high-performance Au/TiO2 photocatalytic nanostructures through the optimization of the synthesis parameters, photocatalytic conditions, and computational modeling. Full article
Show Figures

Graphical abstract

Back to TopTop