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Special Issue "Photocatalysis for Wastewater Treatment"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Catalytic Materials".

Deadline for manuscript submissions: 15 March 2019

Special Issue Editors

Guest Editor
Prof. Dr. Miguel A. Miranda

Instituto de Tecnología Química, Universitat Politècnica de València-Consejo Superior de Investigaciones Científicas, Avenida de los Naranjos s/n, 46022 Valencia, Spain
Website | E-Mail
Interests: photocatalysis; photochemistry; photobiology
Guest Editor
Prof. Dr. M. Luisa Marin

Instituto de Tecnología Química, Universitat Politècnica de València-Consejo Superior de Investigaciones Científicas, Avenida de los Naranjos s/n, 46022 Valencia, Spain
Website | E-Mail
Interests: photocatalysis; photochemistry; photobiology

Special Issue Information

Dear Colleagues,

Starting in the 21st century, our society has faced general access of all the world population to safe water and to the disposal of wastewater without threatening water resources and the environment among non-solved challenges. For example, the vision of European Innovation Partnership on Water (EIP) is: “To stimulate creative and innovative solutions that contribute significantly to tackle water challenges at European and global level”. In fact, since the effluent standards for municipal treatment plants are becoming more restrictive, Water Boards are investing more in innovative technologies for wastewater remediation. As a result, the effluents quality has been drastically enhanced, bringing new opportunities and possibilities to recycle them for agriculture, industrial uses, street cleaning, or recreational uses.

Nevertheless, in recent years, detection of an increasing number of xenobiotics at low concentrations (typically µg/L or ng/L) in aquatic systems constitutes a major concern, as their effect on ecosystems or human health remains uncertain. Examples of those xenobiotics include pharmaceuticals, steroids, hormones, personal care products, antiseptics, surfactants, flame-retardants, industrial additives or gasoline additives, as well as their metabolites or degradation products. Conventional wastewater treatments are not always effective for the removal of these substances; thus, development of effective technologies for dealing with this source of contamination is currently a matter of active research. Catalytic methods may constitute a greener alternative to face degradation of these contaminants.

Among chemical methods, oxidative processes have attracted more attention than chemical reduction of recalcitrant contaminants, that has also been reported but to a much lesser extent and deserves further research efforts. Moreover, solar exposure to remove pollutants constitutes the major abiotic pathway for remediation of natural ecosystems. The use of environmentally-friendly reagents and catalysts, together with solar energy as an abundant and renewable energy resource is the basis of photocatalysis. This combination of catalysis and light has deserved recently the attention of researchers as a highly appealing alternative for wastewater treatment and constitutes the topic of the present Special Issue.

Prof. Dr. Miguel A. Miranda
Prof. Dr. M. Luisa Marin
Guest Editors

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 papers will be 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. Materials is an international peer-reviewed open access semimonthly 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 1800 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

  • effluents
  • oxidation
  • pollutants
  • reaction mechanisms
  • reduction
  • visible light

Published Papers (7 papers)

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Research

Open AccessArticle Impact of TiO2 Nanotubes’ Morphology on the Photocatalytic Degradation of Simazine Pollutant
Materials 2018, 11(11), 2066; https://doi.org/10.3390/ma11112066
Received: 17 July 2018 / Revised: 4 August 2018 / Accepted: 8 August 2018 / Published: 23 October 2018
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Abstract
There are various approaches to enhancing the catalytic properties of TiO2, including modifying its morphology by altering the surface reactivity and surface area of the catalyst. In this study, the primary aim is to enhance the photocatalytic activity by changing the [...] Read more.
There are various approaches to enhancing the catalytic properties of TiO2, including modifying its morphology by altering the surface reactivity and surface area of the catalyst. In this study, the primary aim is to enhance the photocatalytic activity by changing the TiO2 nanotubes’ architecture. The highly ordered infrastructure is favorable for a better charge carrier transfer. It is well known that anodization affects TiO2 nanotubes’ structure by increasing the anodization duration which in turn influence the photocatalytic activity. The characterizations were conducted by FE-SEM (fiend emission scanning electron microscopy), XRD (X-ray diffraction), RAMAN (Raman spectroscopy), EDX (Energy dispersive X-ray spectroscopy), UV-Vis (Ultraviolet visible spectroscopy) and LCMS/MS/MS (liquid chromatography mass spectroscopy). We found that the morphological structure is affected by the anodization duration according to FE-SEM. The photocatalytic degradation shows a photodegradation rate of k = 0.0104 min−1. It is also found that a mineralization of Simazine by our prepared TiO2 nanotubes leads to the formation of cyanuric acid. We propose three Simazine photodegradation pathways with several intermediates identified. Full article
(This article belongs to the Special Issue Photocatalysis for Wastewater Treatment)
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Open AccessArticle Facile Fabrication of Dumbbell-Like β-Bi2O3/Graphene Nanocomposites and Their Highly Efficient Photocatalytic Activity
Materials 2018, 11(8), 1359; https://doi.org/10.3390/ma11081359
Received: 10 July 2018 / Revised: 3 August 2018 / Accepted: 3 August 2018 / Published: 6 August 2018
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Abstract
β-Bi2O3 decorated graphene nanosheets (β-Bi2O3/GN) were prepared by a facile solution mixing method. The crystal structure, surface morphology, and photo absorbance properties of the products were characterized by XRD, SEM, and UV-VIS diffuse reflection, respectively. Moreover, [...] Read more.
β-Bi2O3 decorated graphene nanosheets (β-Bi2O3/GN) were prepared by a facile solution mixing method. The crystal structure, surface morphology, and photo absorbance properties of the products were characterized by XRD, SEM, and UV-VIS diffuse reflection, respectively. Moreover, the effect of graphene content on photocatalytic activity was systematically investigated, and the results indicated that these composites possessed a high degradation rate of Rhodamine B (RhB), which was three times higher than that of bare β-Bi2O3 when graphene content was 1 wt %. This high photocatalytic activity was attributed predominantly to the presence of graphene, which served as an electron collector and transporter to efficiently lengthen the lifetime of the photogenerated charge carriers from β-Bi2O3. Full article
(This article belongs to the Special Issue Photocatalysis for Wastewater Treatment)
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Open AccessArticle Elucidating the Photocatalytic Behavior of TiO2-SnS2 Composites Based on Their Energy Band Structure
Materials 2018, 11(6), 1041; https://doi.org/10.3390/ma11061041
Received: 29 May 2018 / Revised: 12 June 2018 / Accepted: 14 June 2018 / Published: 19 June 2018
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Abstract
TiO2-SnS2 composite semiconducting photocatalysts with different building component ratios were prepared by hydrothermal synthesis (TiO2-SnS2-HT) and by immobilization of commercial TiO2 and SnS2 particles (TiO2-SnS2-COMM). The band gap values, which [...] Read more.
TiO2-SnS2 composite semiconducting photocatalysts with different building component ratios were prepared by hydrothermal synthesis (TiO2-SnS2-HT) and by immobilization of commercial TiO2 and SnS2 particles (TiO2-SnS2-COMM). The band gap values, which determine the catalysts’ photoactivity, were examined by diffuse reflectance spectroscopy and Kubelka–Munk transformations. The catalysts’ surface properties: specific surface area, charge and adsorption capacitance at the solid–solution interface were characterized using BET analysis, potentiometric titration and electrochemical impedance spectroscopy, respectively. The electronic band structure of TiO2-SnS2 photocatalyst, as the key property for the solar-driven photocatalysis, was deduced from the thermodynamic data and the semiconducting parameters (type of semiconductivity, concentration of the charge carriers, flat band potential) obtained by Mott–Schottky analysis. The photoactivity of both composites was studied in photocatalytic treatment of diclofenac (DCF) under simulated solar irradiation and was compared to the benchmark photocatalyst (TiO2 P25) activity. The influence of process parameters, such as pH, H2O2, and composite formulation on the effectiveness of DCF removal and conversion was investigated and discussed by employing response surface modeling (RSM) approach. The photocatalytic efficiency of both composite materials was discussed on the basis of the hetereojunction formation that facilitated the photoelectron transfer, promoting more efficient photocatalytic degradation of DCF. Full article
(This article belongs to the Special Issue Photocatalysis for Wastewater Treatment)
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Open AccessArticle Synthesis of Various TiO2 Micro-/Nano-Structures and Their Photocatalytic Performance
Materials 2018, 11(6), 995; https://doi.org/10.3390/ma11060995
Received: 29 April 2018 / Revised: 29 May 2018 / Accepted: 4 June 2018 / Published: 12 June 2018
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Abstract
TiO2 micro-/nano-structures with different morphologies have been successfully synthesized via a hydrothermal method. The effects of the solvents on the morphology and structure of the obtained products have been studied. The objective of the present paper is to compare the photocatalytic properties [...] Read more.
TiO2 micro-/nano-structures with different morphologies have been successfully synthesized via a hydrothermal method. The effects of the solvents on the morphology and structure of the obtained products have been studied. The objective of the present paper is to compare the photocatalytic properties of the obtained TiO2 products. During the synthesis process, the tetrabutyl titanate and titanium (IV) fluoride were used as the titanium source. The obtained micro-/nano-structures were characterized by field-emission scanning electron microscopy, X-ray diffraction analysis, and nitrogen adsorption-desorption isotherms. The photocatalytic activity of the samples was evaluated by the degradation of Rhodamine B solution under simulated solar irradiation. It is found that the morphologies and structures of TiO2 have a great influence on its photocatalytic activity. Compared with other samples, TiO2 flower clusters assembled with nanorods exhibited a superior photocatalytic activity in the degradation of Rhodamine B. Full article
(This article belongs to the Special Issue Photocatalysis for Wastewater Treatment)
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Open AccessArticle Facile Synthesis of Magnetic Photocatalyst Ag/BiVO4/Mn1−xZnxFe2O4 and Its Highly Visible-Light-Driven Photocatalytic Activity
Materials 2018, 11(5), 810; https://doi.org/10.3390/ma11050810
Received: 23 April 2018 / Revised: 10 May 2018 / Accepted: 15 May 2018 / Published: 16 May 2018
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Abstract
Ag/BiVO4/Mn1−xZnxFe2O4 was synthesized with a dip-calcination in situ synthesis method. This work was hoped to provide a simple method to synthesis three-phase composite. The phase structure, optical properties and magnetic feature were confirmed by [...] Read more.
Ag/BiVO4/Mn1−xZnxFe2O4 was synthesized with a dip-calcination in situ synthesis method. This work was hoped to provide a simple method to synthesis three-phase composite. The phase structure, optical properties and magnetic feature were confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometer (XPS), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflectance spectrophotometer (UV-vis DRS), and vibrating sample magnetometer (VSM). The photocatalytic activity was investigated by Rhodamine B (RhB) photo-degradation under visible light irradiation. The photo-degradation rate of RhB was 94.0~96.0% after only 60 min photocatalytic reaction under visible light irradiation, revealing that it had an excellent visible-light-induced photocatalytic activity. In the fifth recycle, the degradation rate of Ag/BiVO4/Mn1−xZnxFe2O4 still reached to 94.0%. Free radical tunnel experiments confirmed the dominant role of •O2 in the photocatalytic process for Ag/BiVO4/Mn1−xZnxFe2O4. Most importantly, the mechanism that multifunction Ag could enhance photocatalytic activity was explained in detail. Full article
(This article belongs to the Special Issue Photocatalysis for Wastewater Treatment)
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Open AccessArticle New Insights into Sensitization Mechanism of the Doped Ce (IV) into Strontium Titanate
Materials 2018, 11(4), 646; https://doi.org/10.3390/ma11040646
Received: 17 March 2018 / Revised: 17 April 2018 / Accepted: 18 April 2018 / Published: 23 April 2018
Cited by 3 | PDF Full-text (4978 KB) | HTML Full-text | XML Full-text
Abstract
SrTiO3 and Ce4+ doped SrTiO3 were synthesized by a modified sol–gel process. The optimization synthesis parameters were obtained by a series of single factor experiments. Interesting phenomena are observable in Ce4+ doped SrTiO3 systems. Sr2+ in SrTiO [...] Read more.
SrTiO3 and Ce4+ doped SrTiO3 were synthesized by a modified sol–gel process. The optimization synthesis parameters were obtained by a series of single factor experiments. Interesting phenomena are observable in Ce4+ doped SrTiO3 systems. Sr2+ in SrTiO3 system was replaced by Ce4+, which reduced the surface segregation of Ti4+, ameliorated agglomeration, increased specific surface area more than four times compared with pure SrTiO3, and enhanced quantum efficiency for SrTiO3. Results showed that Ce4+ doping increased the physical adsorption of H2O and adsorbed oxygen on the surface of SrTiO3, which produced additional catalytic active centers. Electrons on the 4f energy level for Ce4+ produced new energy states in the band gap of SrTiO3, which not only realized the use of visible light but also led to an easier separation between the photogenerated electrons and holes. Ce4+ repeatedly captured photoelectrons to produce Ce3+, which inhibited the recombination between photogenerated electrons and holes as well as prolonged their lifetime; it also enhanced quantum efficiency for SrTiO3. The methylene blue (MB) degradation efficiency reached 98.7% using 3 mol % Ce4+ doped SrTiO3 as a photocatalyst, indicating highly photocatalytic activity. Full article
(This article belongs to the Special Issue Photocatalysis for Wastewater Treatment)
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Open AccessArticle New Insights into Mn1−xZnxFe2O4 via Fabricating Magnetic Photocatalyst Material BiVO4/Mn1−xZnxFe2O4
Materials 2018, 11(3), 335; https://doi.org/10.3390/ma11030335
Received: 3 January 2018 / Revised: 9 February 2018 / Accepted: 13 February 2018 / Published: 26 February 2018
Cited by 4 | PDF Full-text (3308 KB) | HTML Full-text | XML Full-text
Abstract
BiVO4/Mn1−xZnxFe2O4 was prepared by the impregnation roasting method. XRD (X-ray Diffractometer) tests showed that the prepared BiVO4 is monoclinic crystal, and the introduction of Mn1−xZnxFe2O4 does [...] Read more.
BiVO4/Mn1−xZnxFe2O4 was prepared by the impregnation roasting method. XRD (X-ray Diffractometer) tests showed that the prepared BiVO4 is monoclinic crystal, and the introduction of Mn1−xZnxFe2O4 does not change the crystal structure of BiVO4. The introduction of a soft-magnetic material, Mn1−xZnxFe2O4, was beneficial to the composite photocatalyst’s separation from the liquid solution using an extra magnet after use. UV-vis spectra analysis indicated that Mn1−xZnxFe2O4 enhanced the absorption intensity of visible light for BiVO4. EIS (electrochemical impedance spectroscopy) investigation revealed that the introduction of Mn1−xZnxFe2O4 enhanced the conductivity of BiVO4, further decreasing its electron transfer impedance. The photocatalytic efficiency of BiVO4/Mn1−xZnxFe2O4 was higher than that of pure BiVO4. In other words, Mn1−xZnxFe2O4 could enhance the photocatalytic reaction rate. Full article
(This article belongs to the Special Issue Photocatalysis for Wastewater Treatment)
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