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Environmental Applications of Photocatalytic 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 July 2019) | Viewed by 46612

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Special Issue Editors

Prof. Dr. Luigi Rizzo

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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, Collections and Topics in MDPI journals

Dr. Adrián M.T. Silva

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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, Collections and Topics 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

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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

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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2 pages, 160 KiB

Open AccessEditorial

Environmental Applications of Photocatalytic Processes

by Luigi Rizzo and Adrián M.T. Silva

Catalysts 2020, 10(11), 1264; https://doi.org/10.3390/catal10111264 - 31 Oct 2020

Viewed by 1192

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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8 pages, 4287 KiB

Open AccessArticle

Fast Method for Testing the Photocatalytic Performance of Modified Gypsum

by Magdalena Janus, Kamila Zając, Clemens Ehm and Dietmar Stephan

Catalysts 2019, 9(8), 693; https://doi.org/10.3390/catal9080693 - 15 Aug 2019

Cited by 8 | Viewed by 4978

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 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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15 pages, 6645 KiB

Open AccessArticle

In situ Decolorization Monitoring of Textile Dyes for an Optimized UV-LED/TiO₂ Reactor

by Tecilli Tapia-Tlatelpa, Jose Trull and Luis Romeral

Catalysts 2019, 9(8), 669; https://doi.org/10.3390/catal9080669 - 06 Aug 2019

Cited by 10 | Viewed by 3297

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 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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10 pages, 2659 KiB

Open AccessArticle

High-Efficiency Visible Light Responsive Sulfide KSb₅S₈ Photocatalyst with a Layered Crystal Structure

by Yuanyuan Li, Meijun Wu, Qiang Wang, Kun Wang, He Zhang, Xuejun Quan, Bin Zhang and Dingfeng Yang

Catalysts 2019, 9(6), 529; https://doi.org/10.3390/catal9060529 - 13 Jun 2019

Cited by 4 | Viewed by 2838

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 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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17 pages, 2979 KiB

Open AccessArticle

Immobilised Cerium-Doped Zinc Oxide as a Photocatalyst for the Degradation of Antibiotics and the Inactivation of Antibiotic-Resistant Bacteria

by Ian Zammit, Vincenzo Vaiano, Ana R. Ribeiro, Adrián M. T. Silva, Célia M. Manaia and Luigi Rizzo

Catalysts 2019, 9(3), 222; https://doi.org/10.3390/catal9030222 - 01 Mar 2019

Cited by 30 | Viewed by 4718

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 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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12 pages, 3331 KiB

Open AccessArticle

Photocatalytic Degradation of Humic Acids Using LaFeO₃

by Nazli Turkten, Isabella Natali Sora, Ayse Tomruk and Miray Bekbolet

Catalysts 2018, 8(12), 630; https://doi.org/10.3390/catal8120630 - 06 Dec 2018

Cited by 16 | Viewed by 3494

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 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 LaFe_0.90Cu_0.10O_3−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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14 pages, 5025 KiB

Open AccessArticle

Reduced Graphene Oxide/TiO₂ Nanocomposite: From Synthesis to Characterization for Efficient Visible Light Photocatalytic Applications

by Elena Rommozzi, Marco Zannotti, Rita Giovannetti, Chiara Anna D’Amato, Stefano Ferraro, Marco Minicucci, Roberto Gunnella and Andrea Di Cicco

Catalysts 2018, 8(12), 598; https://doi.org/10.3390/catal8120598 - 01 Dec 2018

Cited by 57 | Viewed by 7578

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 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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14 pages, 4419 KiB

Open AccessArticle

Significantly Enhanced Aqueous Cr(VI) Removal Performance of Bi/ZnO Nanocomposites via Synergistic Effect of Adsorption and SPR-Promoted Visible Light Photoreduction

by Xiaoya Yuan, Zijuan Feng, Jianjun Zhao, Jiawei Niu, Jiasen Liu, Dong Peng and Xin Cheng

Catalysts 2018, 8(10), 426; https://doi.org/10.3390/catal8100426 - 29 Sep 2018

Cited by 20 | Viewed by 3786

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 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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15 pages, 4919 KiB

Open AccessArticle

Photocatalytic Inactivation of Bacteriophage f2 with Ag₃PO₄/g-C₃N₄ Composite under Visible Light Irradiation: Performance and Mechanism

by Rong Cheng, Liang-jie Shen, Jin-hui Yu, Shao-yu Xiang and Xiang Zheng

Catalysts 2018, 8(10), 406; https://doi.org/10.3390/catal8100406 - 20 Sep 2018

Cited by 29 | Viewed by 3633

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 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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26 pages, 4814 KiB

Open AccessReview

Gas Phase Photocatalytic CO₂ Reduction, “A Brief Overview for Benchmarking”

by Shahzad Ali, Monica Claire Flores, Abdul Razzaq, Saurav Sorcar, Chaitanya B. Hiragond, Hye Rim Kim, Young Ho Park, Yunju Hwang, Hong Soo Kim, Hwapyong Kim, Eun Hee Gong, Junho Lee, Dongyun Kim and Su-Il In

Catalysts 2019, 9(9), 727; https://doi.org/10.3390/catal9090727 - 28 Aug 2019

Cited by 58 | Viewed by 10181

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 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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