Special Issue "Environmental Applications of Photocatalytic Processes"

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

Deadline for manuscript submissions: closed (31 July 2019).

Special Issue Editors

Prof. Dr. Luigi Rizzo
E-Mail Website
Guest Editor
Department of Civil Engineering, University of Salerno, 84084 Fisciano, (SA), Italy
Interests: advanced oxidation processes, photocatalytic processes, antibiotic resistance, contaminants of emerging concern, industrial wastewater treatment, wastewater disinfection, wastewater reuse
Special Issues and Collections in MDPI journals
Dr. Adrián M.T. Silva
E-Mail Website
Guest Editor
Laboratory of Separation and Reaction Engineering - Laboratory of Catalysis and Materials (LSRE-LCM), Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal
Interests: water and wastewater treatment, desalination and reuse; advanced oxidation technologies; membrane technology; environmental monitoring
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Photocatalytic processes have been investigated in different environmental applications, from water treatment to the production of solar fuels, but their application at a full scale are still scarce. The scope of this Special Issue is to contribute to both the advance of the knowledge on environmental applications of (photo)catalytic processes, as well as to the understanding of the main challenges to address to push up their application to full scale. The subjects that will be preferably covered by this Special Issue include, but are not limited to: i) water/wastewater treatment; ii) water/wastewater disinfection; iii) water reuse; iv) new photocatalysts; v) solar driven photocatalytic processes; vi) new reactor design; vii) full scale applications; viii) new environmental/energy challenges (e.g., removal of contaminants of emerging concern, production of solar fuels, etc.); and ix) economic evaluation and scale up challenges of photocatalytic processes. This Special Issue will preferably include research papers, but review papers can eventually be submitted only after the authors will contact the Guest Editors and send them an abstract to discuss the suitability and acceptability of the topic for the Special Issue. Review paper proposals are expected to present sound critical overviews of the state of-the-art of a topic from the proposed subjects, to help the reader to discriminate the most relevant results of the research, the possible successful applications of the technology at full scale and, most important, the future trends in the research and the main (environmental/technological) challenges to address.

Dr. Luigi Rizzo
Dr. Adrián M.T. Silva
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.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 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

  • photocatalytic processes
  • photocatalysts
  • wastewater treatment
  • wastewater disinfection
  • urban wastewater
  • industrial wastewater
  • hydrogen production
  • CO2 reduction
  • technology scale-up

Published Papers (10 papers)

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Editorial

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Open AccessEditorial
Environmental Applications of Photocatalytic Processes
Catalysts 2020, 10(11), 1264; https://doi.org/10.3390/catal10111264 - 31 Oct 2020
Viewed by 355
Abstract
Photocatalytic processes have been investigated in different environmental fields, but their applications at full scale are still scarce [...] Full article
(This article belongs to the Special Issue Environmental Applications of Photocatalytic Processes)

Research

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Open AccessArticle
Fast Method for Testing the Photocatalytic Performance of Modified Gypsum
Catalysts 2019, 9(8), 693; https://doi.org/10.3390/catal9080693 - 15 Aug 2019
Cited by 4 | Viewed by 1156
Abstract
The measurement of the photocatalytic activity of building materials is quite time-consuming. Up until now, researchers have mainly used the equipment described in ISO 22197-1 to ISO 22197-4 for the determination of air purification activity, although other apparatus such as colorimeters, UV-Vis/DR spectroscopes [...] Read more.
The measurement of the photocatalytic activity of building materials is quite time-consuming. Up until now, researchers have mainly used the equipment described in ISO 22197-1 to ISO 22197-4 for the determination of air purification activity, although other apparatus such as colorimeters, UV-Vis/DR spectroscopes and equipment for contact angle measurements have also been used. Usually, photocatalytic activity measurements take from one hour up to several hours. In this study, we present a very fast method for the measurement of the photocatalytic activity of gypsum. A specially designed printer with a modified bubblejet cartridge was used to apply a special ink on the surface of gypsum plates. Then the surface was irradiated by UV-A light and every 3 s a picture of the surface was taken. The results showed that the discoloration of the dye occurs after a few seconds of irradiation and the time depends on the amount of photocatalyst used as well as the number of printed ink layers. It was concluded that it is possible to use this method for a quick comparison of the photocatalytic activity of different types of modified gypsum materials. Full article
(This article belongs to the Special Issue Environmental Applications of Photocatalytic Processes)
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Open AccessArticle
In situ Decolorization Monitoring of Textile Dyes for an Optimized UV-LED/TiO2 Reactor
Catalysts 2019, 9(8), 669; https://doi.org/10.3390/catal9080669 - 06 Aug 2019
Cited by 6 | Viewed by 1096
Abstract
Heterogeneous photocatalysis, using photocatalysts in suspension to eliminate diverse contaminants, including textile wastewater, has several advantages. Nevertheless, current absorbance and decolorization measurements imply sample acquisition by extraction at a fixed rate with consequent photocatalyst removal. This study presents online monitoring for the decolorization [...] Read more.
Heterogeneous photocatalysis, using photocatalysts in suspension to eliminate diverse contaminants, including textile wastewater, has several advantages. Nevertheless, current absorbance and decolorization measurements imply sample acquisition by extraction at a fixed rate with consequent photocatalyst removal. This study presents online monitoring for the decolorization of six azo dyes, Orange PX-2R (OP2), Remazol Black B133 (RB), Procion Crimson H-EXL (PC), Procion Navy H-EXL (PN), Procion Blue H-EXL (PB), and Procion Yellow H-EXL (PY), analyzing the spectrum measured in situ by using the light scattering provided by the photocatalyst in suspension. The results obtained have corroborated the feasibility of obtaining absorbance and decolorization measurements, avoiding disturbances in the process due to a decrease in the volume in the reactor. Full article
(This article belongs to the Special Issue Environmental Applications of Photocatalytic Processes)
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Open AccessArticle
High-Efficiency Visible Light Responsive Sulfide KSb5S8 Photocatalyst with a Layered Crystal Structure
Catalysts 2019, 9(6), 529; https://doi.org/10.3390/catal9060529 - 13 Jun 2019
Cited by 2 | Viewed by 993
Abstract
The development of efficient photocatalysts for degrading environmental pollutants in wastewater has drawn considerable attention due to their great potential in industrial applications. Herein, we used a solvothermal method to prepare KSb5S8 with a layered crystal structure. The crystal structure [...] Read more.
The development of efficient photocatalysts for degrading environmental pollutants in wastewater has drawn considerable attention due to their great potential in industrial applications. Herein, we used a solvothermal method to prepare KSb5S8 with a layered crystal structure. The crystal structure of the as-synthesized samples was characterized by powder X-ray diffraction and transmission electron microscope imaging. Our UV-vis diffuse reflectance spectroscopy results indicated that KSb5S8 could absorb visible light, and its optical band gap was 1.62 eV. The photocatalytic activity of KSb5S8 was evaluated in the degradation of methyl orange. A degradation of 73% within 180 min was achieved under visible light irradiation, which was considerably higher than that of commercial P25 and g-C3N4. Theoretical calculations demonstrated that KSb5S8 was an indirect band gap semiconductor. The estimated effective mass of holes ( m h * ) was approximately two times greater than that of electrons ( m e * ) . The large ratio of m h * / m e * might promote separation of photo-induced carriers during the photocatalytic process. On the basis of the layered crystal structure and large m h * / m e * value, KSb5S8 was a high-performance photocatalyst capable of harvesting visible light. This study provides valuable insight that will aid the design of improved sulfide photocatalytic materials with layered crystal structures. Full article
(This article belongs to the Special Issue Environmental Applications of Photocatalytic Processes)
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Open AccessArticle
Immobilised Cerium-Doped Zinc Oxide as a Photocatalyst for the Degradation of Antibiotics and the Inactivation of Antibiotic-Resistant Bacteria
Catalysts 2019, 9(3), 222; https://doi.org/10.3390/catal9030222 - 01 Mar 2019
Cited by 12 | Viewed by 1814
Abstract
The threat of antibiotic resistance to the wellbeing of societies is well established. Urban wastewater treatment plants (UWTPs) are recognised sources for antibiotic resistance dissemination in the environment. Herein a novel cerium-doped zinc oxide (Ce-ZnO) photocatalyst is compared to ZnO and the benchmark [...] Read more.
The threat of antibiotic resistance to the wellbeing of societies is well established. Urban wastewater treatment plants (UWTPs) are recognised sources for antibiotic resistance dissemination in the environment. Herein a novel cerium-doped zinc oxide (Ce-ZnO) photocatalyst is compared to ZnO and the benchmark TiO2-P25 in the immobilised form on a metallic support, to evaluate a photocatalytic process as a possible tertiary treatment in UWTPs. The catalysts were compared for the removal of two antibiotics, trimethoprim (TMP) and sulfamethoxazole (SMX), and for the inactivation of Escherichia coli (E. coli) strain DH5-Alpha in isotonic sodium chloride solution and of autochthonous bacteria in real secondary wastewater. In real wastewater, E. coli and other coliforms were monitored, as well as the respective fractions resistant to ofloxacin and azithromycin. In parallel, Pseudomonas aeruginosa and the respective sub-population resistant to ofloxacin or ciprofloxacin were also monitored. Photocatalysis with both ZnO and Ce-ZnO was faster than using TiO2-P25 at degrading the antibiotics, with Ce-ZnO the fastest against SMX but slower than undoped ZnO in the removal of TMP. Ce-ZnO catalyst reuse in the immobilised form produced somewhat slower kinetics maintained >50% of the initial activity, even after five cycles of use. Approximately 3 log10 inactivation of E. coli in isotonic sodium chloride water was recorded with reproducible results. In the removal of autochthonous bacteria in real wastewater, Ce-ZnO performed better (more than 2 log values higher) than TiO2-P25. In all cases, E. coli and other coliforms, including their resistant subpopulations, were inactivated at a higher rate than P. aeruginosa. With short reaction times no evidence for enrichment of resistance was observed, yet with extended reaction times low levels of bacterial loads were not further inactivated. Overall, Ce-ZnO is an easy and cheap photocatalyst to produce and immobilise and the one that showed higher activity than the industry standard TiO2-P25 against the tested antibiotics and bacteria, including antibiotic-resistant bacteria. Full article
(This article belongs to the Special Issue Environmental Applications of Photocatalytic Processes)
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Open AccessArticle
Photocatalytic Degradation of Humic Acids Using LaFeO3
Catalysts 2018, 8(12), 630; https://doi.org/10.3390/catal8120630 - 06 Dec 2018
Cited by 3 | Viewed by 1117
Abstract
TiO2 photocatalytic degradation of dissolved organic matter (DOM), namely humic substances composed of humic (HA) and fulvic acids, has been investigated for decades. However, the application of non-TiO2 photocatalysis for this purpose has only received recent attention. Aiming to fill this [...] Read more.
TiO2 photocatalytic degradation of dissolved organic matter (DOM), namely humic substances composed of humic (HA) and fulvic acids, has been investigated for decades. However, the application of non-TiO2 photocatalysis for this purpose has only received recent attention. Aiming to fill this gap, this study was performed to elucidate the photocatalytic degradation of HAs using the novel photocatalyst LaFeO3 (LF) under simulated solar light irradiation. HA was selectively fractionated by ultrafiltration to two different molecular size fractions representing high molecular fraction as 100 kDa and lower molecular size fraction comprised of humic components expressing size fractions smaller than 30 kDa. Photocatalyst LF was prepared by the citrate auto-combustion method and characterized by using various techniques and Brunauer–Emmett–Teller (BET) surface area. Ultraviolet-visible (UV-vis) and excitation-emission matrix (EEM) fluorescence spectroscopic features were used to characterize the treated HA and photocatalytic mineralization extend was followed by dissolved organic carbon (DOC) contents. Photocatalytic performance of LF was compared to the metal modified version as Cu-doped LF. Highest mineralization was achieved upon the use of a photocatalyst dose of 0.25 mg/mL of LaFe0.90Cu0.10O3−δ (Cu-LF) for 30 kDaHA, whereas lowest mineralization was attained for 100 kDaHA upon the use of LF. Photocatalytic degradation kinetics indicated the possible use of LF and Cu-LF for the degradation of HA. Full article
(This article belongs to the Special Issue Environmental Applications of Photocatalytic Processes)
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Open AccessArticle
Reduced Graphene Oxide/TiO2 Nanocomposite: From Synthesis to Characterization for Efficient Visible Light Photocatalytic Applications
Catalysts 2018, 8(12), 598; https://doi.org/10.3390/catal8120598 - 01 Dec 2018
Cited by 27 | Viewed by 2231
Abstract
In this study, a green and facile thermal reduction of graphene oxide using an eco-friendly system of d-(+)-glucose and NH4OH for the preparation of reduced graphene oxide was described. The obtained reduced graphene oxide dispersion was characterized by SEM, Dynamic [...] Read more.
In this study, a green and facile thermal reduction of graphene oxide using an eco-friendly system of d-(+)-glucose and NH4OH for the preparation of reduced graphene oxide was described. The obtained reduced graphene oxide dispersion was characterized by SEM, Dynamic Light Scattering, Raman and X-Ray Photoelectron Spectroscopy. TiO2 nanoparticles and reduced graphene oxide nanocomposites were successively prepared and used in the preparation of heterogeneous photocatalysts that were characterized by Atomic Force Microscopy and Photoluminescence Spectroscopy and subsequently tested as visible light photocatalysts for the photodegradation of Alizarin Red S in water as target pollutant. Obtained results of photocatalytic tests regarding the visible light photocatalytic degradation of Alizarin Red S demonstrated that the use of reduced graphene oxide in combination with TiO2 led to a significant improvement for both adsorption of Alizarin Red S on the catalyst surface and photodegradation efficiencies when compared to those obtained with not doped TiO2. Full article
(This article belongs to the Special Issue Environmental Applications of Photocatalytic Processes)
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Open AccessArticle
Significantly Enhanced Aqueous Cr(VI) Removal Performance of Bi/ZnO Nanocomposites via Synergistic Effect of Adsorption and SPR-Promoted Visible Light Photoreduction
Catalysts 2018, 8(10), 426; https://doi.org/10.3390/catal8100426 - 29 Sep 2018
Cited by 11 | Viewed by 1415
Abstract
Bismuth nanoparticles (BiNPs) and Zinc Oxide photocatalysts (BiNPs/ZnO) with different Bi loadings were successfully prepared via a facile chemical method. Their morphology and structure were thoroughly characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron [...] Read more.
Bismuth nanoparticles (BiNPs) and Zinc Oxide photocatalysts (BiNPs/ZnO) with different Bi loadings were successfully prepared via a facile chemical method. Their morphology and structure were thoroughly characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-Vis (Ultraviolet-Visible) diffuse reflectance spectroscopy (DRS), photoluminescence spectra (PL), and electrochemical impedance spectroscopy (EIS). The results showed that a modification of hexagonal wurtzite-phase ZnO nanoparticles with Bi is achievable with an intimate interfacial interaction within its composites. The performance of the photocatalytic Cr(VI) removal under visible light irradiation indicated that BiNPs/ZnO exhibited a superior removal performance to bare ZnO, Bi, and the counterpart sample prepared using a physical mixing method. The excellent performance of the BiNPs/ZnO photocatalysts could be ascribed to the synergistic effect between the considerable physical Cr (VI) adsorption and enhanced absorption intensity in the visible light region, due to the surface plasmon resonance (SPR) as well as the effective transfer and separation of the photogenerated charge carriers at the interface. Full article
(This article belongs to the Special Issue Environmental Applications of Photocatalytic Processes)
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Open AccessArticle
Photocatalytic Inactivation of Bacteriophage f2 with Ag3PO4/g-C3N4 Composite under Visible Light Irradiation: Performance and Mechanism
Catalysts 2018, 8(10), 406; https://doi.org/10.3390/catal8100406 - 20 Sep 2018
Cited by 11 | Viewed by 1261
Abstract
Water-borne virus pollution has caused great harm and attracted widespread attention in many countries. Visible-light-driven photocatalysis is considered as a promising process for disinfection. In this study, Ag3PO4/g-C3N4 (AgCN) composites were synthesized by hydrothermal method. The [...] Read more.
Water-borne virus pollution has caused great harm and attracted widespread attention in many countries. Visible-light-driven photocatalysis is considered as a promising process for disinfection. In this study, Ag3PO4/g-C3N4 (AgCN) composites were synthesized by hydrothermal method. The photocatalytic disinfection was investigated using bacteriophage f2 as the model virus. Moreover, the effects of pH and humic acid on photocatalytic disinfection were studied. Meanwhile, the mechanism of enhanced disinfection by Ag3PO4/g-C3N4 was systematically investigated by radical scavenger experiments. The results show that Ag3PO4 particles were uniformly distributed on g-C3N4 sheets. By means of photoluminescence spectrometer analysis, it is confirmed that a lower carrier recombination rate for Ag3PO4/g-C3N4 was achieved compared with Ag3PO3 and g-C3N4. Meanwhile, complete inactivation of f2 with concentration of 3 × 106 PFU/mL was reached within 80 min in the presence of Ag3PO4/g-C3N4 composite. The pH had little effect on removal efficiency overall, while the existence of humic acid resulted in a significant negative effect on the inactivation of f2 due to the optical shielding and absorption of humic acid. Recycling tests of Ag3PO4/g-C3N4 confirmed that Ag3PO4/g-C3N4 presented superior stability. The results from radical scavenger experiments indicated that holes (h+) and hydroxyl radicals (·OH) played important roles in photocatalytic disinfection process. Full article
(This article belongs to the Special Issue Environmental Applications of Photocatalytic Processes)
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Review

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Open AccessReview
Gas Phase Photocatalytic CO2 Reduction, “A Brief Overview for Benchmarking”
Catalysts 2019, 9(9), 727; https://doi.org/10.3390/catal9090727 - 28 Aug 2019
Cited by 18 | Viewed by 1431
Abstract
Photocatalytic CO2 reduction is emerging as an affordable route for abating its ever increasing concentration. For commercial scale applications, many constraints are still required to be addressed. A variety of research areas are explored, such as development of photocatalysts and photoreactors, reaction [...] Read more.
Photocatalytic CO2 reduction is emerging as an affordable route for abating its ever increasing concentration. For commercial scale applications, many constraints are still required to be addressed. A variety of research areas are explored, such as development of photocatalysts and photoreactors, reaction parameters and conditions, to resolve these bottlenecks. In general, the photocatalyst performance is mostly adjudged in terms of its ability to only produce hydrocarbon products, and other vital parameters such as light source, reaction parameters, and type of photoreactors used are not normally given appropriate attention. This makes a comprehensive comparison of photocatalytic performance quite unrealistic. Hence, probing the photocatalytic performance in terms of apparent quantum yield (AQY) with the consideration of certain process and experimental parameters is a more reasonable and prudent approach. The present brief review portrays the importance and impact of aforementioned parameters in the field of gas phase photocatalytic CO2 reduction. Full article
(This article belongs to the Special Issue Environmental Applications of Photocatalytic Processes)
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