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Open AccessArticle

Multitarget Evaluation of the Photocatalytic Activity of P25-SiO₂ Prepared by Atomic Layer Deposition

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Catalysts 2020, 10(4), 450; https://doi.org/10.3390/catal10040450 - 22 Apr 2020

Cited by 2

Abstract

This work presents the evaluation of the photocatalytic activity of P25 TiO₂ particles, coated with SiO₂, using atomic layer deposition (ALD) for the photocatalytic removal of methylene blue, oxidation of methanol and inactivation of Escherichia coli bacteria in water and [...] Read more.

This work presents the evaluation of the photocatalytic activity of P25 TiO₂ particles, coated with SiO₂, using atomic layer deposition (ALD) for the photocatalytic removal of methylene blue, oxidation of methanol and inactivation of Escherichia coli bacteria in water and its comparative evaluation with bare P25 TiO₂. Two different reactor configurations were used, a slurry reactor with the catalyst in suspension, and a structured reactor with the catalyst immobilized in macroporous foams, that enables the long-term operation of the process in continuous mode, without the necessity of separation of the particles. The results show that the incorporation of SiO₂ decreases the efficiency of the photocatalytic oxidation of methanol, whereas a significant improvement in the removal of methylene blue is achieved, and no significant changes are observed in the photocatalytic inactivation of bacteria. Adsorption tests showed that the improvements, observed in the removal of methylene blue by the incorporation of SiO₂, was mainly due to an increase in its adsorption. The improvement in the adsorption step as part of the global photocatalytic process led to a significant increase in its removal efficiency. Similar conclusions were reached for bacterial inactivation where the loss of photocatalytic efficiency, suggested by the methanol oxidation tests, was counteracted with a better adherence of bacteria to the catalyst that improved its elimination. With respect to the use of macroporous foams as support, a reduction in the photocatalytic efficiency is observed, as expected from the decrease in the available surface area. Nevertheless, this lower efficiency can be counteracted by the operational improvement derived from the easy catalyst reuse. Full article

(This article belongs to the Special Issue Novel Heterogeneous Catalysts for Advanced Oxidation Processes (AOPs))

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Open AccessArticle

Electrochemical Oxidation of an Organic Dye Adsorbed on Tin Oxide and Antimony Doped Tin Oxide Graphene Composites

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Farbod Sharif

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Edward P. L. Roberts

Catalysts 2020, 10(2), 263; https://doi.org/10.3390/catal10020263 - 21 Feb 2020

Abstract

Electrochemical regeneration suffers from low regeneration efficiency due to side reactions like oxygen evolution, as well as oxidation of the adsorbent. In this study, electrically conducting nanocomposites, including graphene/SnO₂ (G/SnO₂) and graphene/Sb-SnO₂ (G/Sb-SnO₂) were successfully synthesized and [...] Read more.

Electrochemical regeneration suffers from low regeneration efficiency due to side reactions like oxygen evolution, as well as oxidation of the adsorbent. In this study, electrically conducting nanocomposites, including graphene/SnO₂ (G/SnO₂) and graphene/Sb-SnO₂ (G/Sb-SnO₂) were successfully synthesized and characterized using nitrogen adsorption, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. Thereafter, the adsorption and electrochemical regeneration performance of the nanocomposites were tested using methylene blue as a model contaminant. Compared to bare graphene, the adsorption capacity of the new composites was ≥40% higher, with similar isotherm behavior. The adsorption capacity of G/SnO₂ and G/Sb-SnO₂ were effectively regenerated in both NaCl and Na₂SO₄ electrolytes, requiring as little charge as 21 C mg⁻¹ of adsorbate for complete regeneration, compared to >35 C mg⁻¹ for bare graphene. Consecutive loading and anodic electrochemical regeneration cycles of the nanocomposites were carried out in both NaCl and Na₂SO₄ electrolytes without loss of the nanocomposite, attaining high regeneration efficiencies (ca. 100%). Full article

(This article belongs to the Special Issue Novel Heterogeneous Catalysts for Advanced Oxidation Processes (AOPs))

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Open AccessArticle

Fenton and Photo-Fenton Nanocatalysts Revisited from the Perspective of Life Cycle Assessment

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Sara Feijoo

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Jorge González-Rodríguez

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Lucía Fernández

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Carlos Vázquez-Vázquez

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Gumersindo Feijoo

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María Teresa Moreira

Catalysts 2020, 10(1), 23; https://doi.org/10.3390/catal10010023 - 24 Dec 2019

Cited by 6

Abstract

This study provides an overview of the environmental impacts associated with the production of different magnetic nanoparticles (NPs) based on magnetite (Fe₃O₄), with a potential use as heterogeneous Fenton or photo-Fenton catalysts in wastewater treatment applications. The tendency of [...] Read more.

This study provides an overview of the environmental impacts associated with the production of different magnetic nanoparticles (NPs) based on magnetite (Fe₃O₄), with a potential use as heterogeneous Fenton or photo-Fenton catalysts in wastewater treatment applications. The tendency of Fe₃O₄ NPs to form aggregates in water makes necessary their decoration with stabilizing agents, in order to increase their catalytic activity. Different stabilizing agents were considered in this study: poly(acrylic acid) (PAA), polyethylenimine (PEI) and silica (SiO₂), as well as the immobilization of the magnetite-based catalysts in a mesoporous silica matrix, SBA-15. In the case of photo-Fenton catalysts, combinations of magnetite NPs with semiconductors were evaluated, so that magnetic recovery of the nanomaterials is possible, thus allowing a safe discharge free of NPs. The results of this study suggest that magnetic nanoparticles coated with PEI or PAA were the most suitable option for their applications in heterogeneous Fenton processes, while ZnO-Fe₃O₄ NPs provided an interesting approach in photo-Fenton. This work showed the importance of identifying the relevance of nanoparticle production strategy in the environmental impacts associated with their use. Full article

(This article belongs to the Special Issue Novel Heterogeneous Catalysts for Advanced Oxidation Processes (AOPs))

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Open AccessArticle

Biochar-Supported FeS/Fe₃O₄ Composite for Catalyzed Fenton-Type Degradation of Ciprofloxacin

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Catalysts 2019, 9(12), 1062; https://doi.org/10.3390/catal9121062 - 13 Dec 2019

Cited by 5

Abstract

The Fenton-type oxidation catalyzed by iron minerals is a cost-efficient and environment-friendly technology for the degradation of organic pollutants in water, but their catalytic activity needs to be enhanced. In this work, a novel biochar-supported composite containing both iron sulfide and iron oxide [...] Read more.

The Fenton-type oxidation catalyzed by iron minerals is a cost-efficient and environment-friendly technology for the degradation of organic pollutants in water, but their catalytic activity needs to be enhanced. In this work, a novel biochar-supported composite containing both iron sulfide and iron oxide was prepared, and used for catalytic degradation of the antibiotic ciprofloxacin through Fenton-type reactions. Dispersion of FeS/Fe₃O₄ nanoparticles was observed with scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). Formation of ferrous sulfide (FeS) and magnetite (Fe₃O₄) in the composite was validated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Ciprofloxacin (initial concentration = 20 mg/L) was completely degraded within 45 min in the system catalyzed by this biochar-supported magnetic composite at a dosage of 1.0 g/L. Hydroxyl radicals (·OH) were proved to be the major reactive species contributing to the degradation reaction. The biochar increased the production of ·OH, but decreased the consumption of H₂O₂, and helped transform Fe³⁺ into Fe²⁺, according to the comparison studies using the unsupported FeS/Fe₃O₄ as the catalyst. All the three biochars prepared by pyrolysis at different temperatures (400, 500 and 600 °C) were capable for enhancing the reactivity of the iron compound catalyst. Full article

(This article belongs to the Special Issue Novel Heterogeneous Catalysts for Advanced Oxidation Processes (AOPs))

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Open AccessArticle

Wet Peroxide Oxidation of Paracetamol Using Acid Activated and Fe/Co-Pillared Clay Catalysts Prepared from Natural Clays

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Adriano Santos Silva

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Marzhan Seitovna Kalmakhanova

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Bakytgul Kabykenovna Massalimova

, Juliana G. Sgorlon,

Diaz de Tuesta Jose Luis

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Helder T. Gomes

Catalysts 2019, 9(9), 705; https://doi.org/10.3390/catal9090705 - 22 Aug 2019

Cited by 6

Abstract

Many pharmaceuticals have been recently identified at trace levels worldwide in the aquatic environment. Among them, the highly consumed paracetamol (PCM), an analgesic and antipyretic drug, is largely being accumulated in the aquatic environment due to inefficient removal by conventional sewage treatment plants. [...] Read more.

Many pharmaceuticals have been recently identified at trace levels worldwide in the aquatic environment. Among them, the highly consumed paracetamol (PCM), an analgesic and antipyretic drug, is largely being accumulated in the aquatic environment due to inefficient removal by conventional sewage treatment plants. This work deals with the treatment of PCM, used as a model pharmaceutical contaminant of emerging concern, by catalytic wet peroxide oxidation using clay-based materials as catalysts. The catalysts were prepared from natural clays, extracted from four different deposits using acid-activated treatment, calcination, and pillarization with Fe and Co. Pillared clays show the highest catalytic activity owing to the presence of metals, allowing to remove completely the PCM after 6 h under the following operating conditions: C_PCM = 100 mg L⁻¹, C_H_₂O_₂ = 472 mg L⁻¹, C_cat = 2.5 g L⁻¹, initial pH = 3.5 and T = 80 °C. The prepared materials presented high stability since leached iron was measured at the end of reaction and found to be lower than 0.1 mg L⁻¹. Full article

(This article belongs to the Special Issue Novel Heterogeneous Catalysts for Advanced Oxidation Processes (AOPs))

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Open AccessArticle

Magnetic Nanoparticles for Photocatalytic Ozonation of Organic Pollutants

by

Carla A. Orge

, O. Salomé G. P. Soares,

Patrícia S. F. Ramalho

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M. Fernando R. Pereira

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Joaquim L. Faria

Catalysts 2019, 9(9), 703; https://doi.org/10.3390/catal9090703 - 22 Aug 2019

Cited by 2

Abstract

Magnetic nanoparticles (MNP) composed of iron oxide (or other metal–FeO cores) coated with carbon produced by chemical vapour decomposition (CVD) were used in the photocatalytic ozonation of oxamic acid (OMA) which we selected as a model pollutant. The incorporation of Ag and Cu [...] Read more.

Magnetic nanoparticles (MNP) composed of iron oxide (or other metal–FeO cores) coated with carbon produced by chemical vapour decomposition (CVD) were used in the photocatalytic ozonation of oxamic acid (OMA) which we selected as a model pollutant. The incorporation of Ag and Cu on FeO enhanced the efficiency of the process. The carbon phase significantly increased the photocatalytic activity towards the conversion of OMA. As for the synthesis process, raising the temperature of CVD improved the performance of the produced photocatalysts. The obtained results suggested that the carbon phase is directly related to high catalytic activity. The most active photocatalyst ([email protected]_CVD850) was used in the removal of other compounds (dyes, industrial pollutants and herbicides) from water and high mineralization levels were attained. This material was also revealed to be stable during reutilisation. Full article

(This article belongs to the Special Issue Novel Heterogeneous Catalysts for Advanced Oxidation Processes (AOPs))

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Open AccessArticle

Heterogeneous Fenton-Like Degradation of p-Nitrophenol over Tailored Carbon-Based Materials

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O. S. G. P. Soares

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Carmen S. D. Rodrigues

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Luis M. Madeira

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M. F. R. Pereira

Catalysts 2019, 9(3), 258; https://doi.org/10.3390/catal9030258 - 14 Mar 2019

Cited by 12

Abstract

Activated carbon (AC), carbon xerogel (XG), and carbon nanotubes (CNT), with and without N-functionalities, were prepared. Catalysts were obtained after impregnation of these materials with 2 wt.% of iron. The materials were characterized in terms of N₂ adsorption at −196 °C, elemental [...] Read more.

Activated carbon (AC), carbon xerogel (XG), and carbon nanotubes (CNT), with and without N-functionalities, were prepared. Catalysts were obtained after impregnation of these materials with 2 wt.% of iron. The materials were characterized in terms of N₂ adsorption at −196 °C, elemental analysis (EA), and the pH at the point of zero charge (pH_PZC). The p-nitrophenol (PNP) degradation and mineralization (assessed in terms of total organic carbon–TOC–removal) were evaluated during adsorption, catalytic wet peroxidation (CWPO), and Fenton process. The textural and chemical properties of the carbon-based materials play an important role in such processes, as it was found that the support with the highest surface area -AC- presents the best performance in adsorption, whereas the materials with the highest mesopore surface area -XG or Fe/XG- lead to best removals by oxidation processes (for XG it was achieved 39.7 and 35.0% and for Fe/XG 45.4 and 41.7% for PNP and TOC, respectively). The presence of N-functionalities increases such removals. The materials were reused in consecutive cycles: the carbon-based materials were deactivated by hydrogen peroxide, while the catalysts showed high stability and no Fe leaching. For the support with superior performances -XG-, the effect of nitrogen content was also evaluated. The removals increase with the increase of the nitrogen content, the maximum removals (81% and 65% for PNP and TOC, respectively) being reached when iron supported on a carbon xerogel doped with melamine was used as catalyst. Full article

(This article belongs to the Special Issue Novel Heterogeneous Catalysts for Advanced Oxidation Processes (AOPs))

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Open AccessArticle

Facile Synthesis of Bi₂MoO₆ Microspheres Decorated by CdS Nanoparticles with Efficient Photocatalytic Removal of Levfloxacin Antibiotic

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Catalysts 2018, 8(10), 477; https://doi.org/10.3390/catal8100477 - 19 Oct 2018

Cited by 5

Abstract

Developing high-efficiency and stable visible-light-driven (VLD) photocatalysts for removal of toxic antibiotics is still a huge challenge at present. Herein, a novel CdS/Bi₂MoO₆ heterojunction with CdS nanoparticles decorated Bi₂MoO₆ microspheres has been obtained by a simple solvothermal-precipitation-calcination [...] Read more.

Developing high-efficiency and stable visible-light-driven (VLD) photocatalysts for removal of toxic antibiotics is still a huge challenge at present. Herein, a novel CdS/Bi₂MoO₆ heterojunction with CdS nanoparticles decorated Bi₂MoO₆ microspheres has been obtained by a simple solvothermal-precipitation-calcination method. 1.0CdS/Bi₂MoO₆ has stronger light absorption ability and highest photocatalytic activity with levofloxacin (LEV) degradation efficiency improving 6.2 or 12.6 times compared to pristine CdS or Bi₂MoO₆. CdS/Bi₂MoO₆ is very stable during cycling tests, and no appreciable activity decline and microstructural changes are observed. Results signify that the introduction of CdS could enhance the light absorption ability and dramatically boost the separation of charge carriers, leading to the excellent photocatalytic performance of the heterojunction. This work demonstrates that flower-like CdS/ Bi₂MoO₆ is an excellent photocatalyst for the efficient removal of the LEV antibiotic. Full article

(This article belongs to the Special Issue Novel Heterogeneous Catalysts for Advanced Oxidation Processes (AOPs))

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