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4 pages, 178 KiB

Open AccessEditorial

Environmental Catalysis for Water Remediation—Preface to the Special Issue

by Silvia Álvarez Torrellas and Juan García Rodríguez

Catalysts 2024, 14(3), 178; https://doi.org/10.3390/catal14030178 - 3 Mar 2024

Viewed by 1461

Abstract

Water is a basic resource and is required by all living beings on our planet [...] Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

Research

Jump to: Editorial

13 pages, 3802 KiB

Open AccessArticle

Synthesis and Application of Egg Shell Biochar for As(V) Removal from Aqueous Solutions

by Asma Akram, Shazma Muzammal, Muhammad Bilal Shakoor, Sajid Rashid Ahmad, Asim Jilani, Javed Iqbal, Abdullah G. Al-Sehemi, Abul Kalam and Samia Faisal O. Aboushoushah

Catalysts 2022, 12(4), 431; https://doi.org/10.3390/catal12040431 - 11 Apr 2022

Cited by 11 | Viewed by 3988

Abstract

Arsenic in water bodies has increased to toxic levels and become a major issue worldwide. Among various treatment methods, the removal of As from polluted water with low-cost and environmental-friendly sorbents such as biochar is considered a promising technique nowadays. In a recent [...] Read more.

Arsenic in water bodies has increased to toxic levels and become a major issue worldwide. Among various treatment methods, the removal of As from polluted water with low-cost and environmental-friendly sorbents such as biochar is considered a promising technique nowadays. In a recent experiment, the treatment of As-contaminated water using egg shell biochar was studied. Various parameters affecting the sorption, such as pH, contact time, sorbent dose, As(V) concentration and the effects of anions, were also examined. The results revealed that at a pH of 4.5, a maximum sorption of 6.3 mg g⁻¹ was observed, and the As(V) removal was 96% with an As concentration of 0.6 mg L⁻¹ and a sorbent dose of 0.9 g L⁻¹. At a contact time of 2 h (120 min), a maximum sorption of 6.3 mg g⁻¹ was noted with a removal percentage of 96%. The sorption of As(V) was obtained at an optimal sorbent dose of 0.9 g L⁻¹. The SEM-EDS data illustrated that biochar consisted of a large number of active sites for As(V) adsorption, and As appeared on the biochar surface after the sorption experiments. Moreover, XPS analyses also confirmed the presence of As(V) on the biochar surface after treatment with As-contaminated water. In a nutshell, the results of this study demonstrate that egg shell biochar has notable efficiency in the removal of As(V) from aqueous solution and that egg shell biochar could be a cost-effective and environmental-friendly sorbent for the treatment of As(V)-contaminated water, specifically in developing countries. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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28 pages, 5242 KiB

Open AccessArticle

Photocatalytic Performance of Carbon-Containing CuMo-Based Catalysts under Sunlight Illumination

by Paula Muñoz-Flores, Po S. Poon, Catherine Sepulveda, Conchi O. Ania and Juan Matos

Catalysts 2022, 12(1), 46; https://doi.org/10.3390/catal12010046 - 1 Jan 2022

Cited by 10 | Viewed by 2451

Abstract

Carbon-doped nanostructured CuMo-based photocatalysts were prepared by solvothermal synthesis. Two thermal treatments—oxidative and inert atmosphere—were used for the synthesis of the catalysts, and the influence of spherical carbon structures upon the crystalline phases on the photocatalytic activity and stability was studied. XRD showed [...] Read more.

Carbon-doped nanostructured CuMo-based photocatalysts were prepared by solvothermal synthesis. Two thermal treatments—oxidative and inert atmosphere—were used for the synthesis of the catalysts, and the influence of spherical carbon structures upon the crystalline phases on the photocatalytic activity and stability was studied. XRD showed the catalysts are nanostructured and composed by a mixture of copper (Cu, Cu₂O, and CuO) and molybdenum (MoO₂ and MoO₃) crystalline phases. The catalysts were used for the degradation of yellow 5 under solar light. A remarkable leaching of Mo both in dark and under solar irradiation was observed and quantified. This phenomenon was responsible for the loss of photocatalytic activity for the degradation of the dye on the Mo-containing series. Conversely, the Cu-based photocatalysts were stable, with no leaching observed after 6 h irradiation and with a higher conversion of yellow 5 compared with the Mo- and CuMo series. The stability of Cu-based catalysts was attributed to a protective effect of spherical carbon structures formed during the solvothermal synthesis. Regarding the catalysts’ composition, sample Cu4-800-N₂ prepared by pyrolysis exhibited up to 4.4 times higher photoactivity than that of the pristine material, which is attributed to a combined effect of an enhanced surface area and micropore volume generated during the pyrolytic treatment due to the presence of the carbon component in the catalyst. Scavenger tests have revealed that the mechanism for tartrazine degradation on irradiated Cu-based catalysts involves successive attacks of •OH radicals. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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15 pages, 2913 KiB

Open AccessArticle

Degradation of Dibutyl Phthalate Plasticizer in Water by High-Performance Iro₂-Ta₂O₅/Ti Electrocatalytic Electrode

by Jia-Ming Xu, Shu-Hsien Chou, Ying Zhang, Mohanraj Kumar and Shan-Yi Shen

Catalysts 2021, 11(11), 1368; https://doi.org/10.3390/catal11111368 - 13 Nov 2021

Cited by 8 | Viewed by 2321

Abstract

Dibutyl phthalate (DBP) in the presence of a wastewater system is harmful to the environment and interferes with the human’s endocrine system. For wastewater treatment, DBP is very difficult to be decomposed by biotechniques and many catalytic processes have been developed. Among them, [...] Read more.

Dibutyl phthalate (DBP) in the presence of a wastewater system is harmful to the environment and interferes with the human’s endocrine system. For wastewater treatment, DBP is very difficult to be decomposed by biotechniques and many catalytic processes have been developed. Among them, the electrocatalytic oxidation (EO) technique has been proven to possess high degradation efficiency of various organic compounds in wastewater. In this study, an electrocatalytic electrode of iridium-tantalum/titanium (IrO₂-Ta₂O₅/Ti) was employed as the anode and graphite as the cathode to decompose DBP substances in the water. According to experimental results, the high removal efficiency of DBP and total organic carbon (TOC) of 90% and 56%, respectively, could be obtained under a voltage gradient of 10 V/cm for 60 min. Compared with other photocatalysis degradation, the IrO₂-Ta₂O₅/Ti electrode could shorten about half the treatment time and electric power based on the same removal efficiency of DBP (i.e., photocatalysis requires 0.225~0.99 KWh). Results also indicated that the production of hydroxyl radical (•OH) in the electrocatalytic electrode played a key role for decomposing the DBP. Moreover, the pH and conductivity of water containing DBP were slightly changed and eventually remained in a stable state during the EO treatment. In addition, the removal efficiency of DBP could still remain about 90% after using the IrO₂-Ta₂O₅/Ti electrode three times and the surface structure of the IrO₂-Ta₂O₅/Ti electrode was stable. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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24 pages, 6970 KiB

Open AccessArticle

Photocatalytic Properties of a Novel Keratin char-TiO₂ Composite Films Made through the Calcination of Wool Keratin Coatings Containing TiO₂ Precursors

by Jinyuan Zhang, Hui Zhang, Wenjun Li, Limeng Yang, Hailiang Wu and Ningtao Mao

Catalysts 2021, 11(11), 1366; https://doi.org/10.3390/catal11111366 - 13 Nov 2021

Cited by 3 | Viewed by 2326

Abstract

In this study, the photocatalytic properties of novel keratin char-TiO₂ composite films, made through the calcination of wool keratin coatings containing TiO₂ precursors at 400 °C, were investigated for the photodegradation of organic contaminants under visible light irradiation. Its structural characteristics [...] Read more.

In this study, the photocatalytic properties of novel keratin char-TiO₂ composite films, made through the calcination of wool keratin coatings containing TiO₂ precursors at 400 °C, were investigated for the photodegradation of organic contaminants under visible light irradiation. Its structural characteristics and photocatalytic performance were systematically examined. It was shown that a self-cleaning hydrophobic keratin char-TiO₂ composite film containing meso- and micro-pores was formed after the keratin—TiO₂ precursors coating was calcined. In comparison with calcinated TiO₂ films, the keratin char-TiO₂ composite films doped with the elements of C, N, and S from keratins resulted in decreased crystallinity and a larger water contact angle. The bandgap of the char-TiO₂ composite films increased slightly from 3.26 to 3.32 eV, and its separation of photogenerated charge carriers was inhibited to a certain degree. However, it exhibited higher photodegradation efficiency to methyl blue (MB) effluents than the pure calcinated TiO₂ films. This was mainly because of its special porous structure, large water contact angle, and high adsorption energy towards organic pollutants, confirmed by the density functional theory calculations. The main active species were ¹O₂ radicals in the MB photodegradation process. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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17 pages, 2964 KiB

Open AccessFeature PaperArticle

Insights into the Kinetics Degradation of Bisphenol A by Catalytic Wet Air Oxidation with Metals Supported onto Carbon Nanospheres

by Estrella Serra-Pérez and Juan García Rodríguez

Catalysts 2021, 11(11), 1293; https://doi.org/10.3390/catal11111293 - 27 Oct 2021

Viewed by 2034

Abstract

Emerging pollutants are an increasing problem in wastewater globally. Bisphenol A (BPA) is one compound belonging to this group. This work proposes the study of the employment of several metal-supported (2 wt. %) carbon nanospheres (CNS) for BPA degradation by catalytic wet-air oxidation. [...] Read more.

Emerging pollutants are an increasing problem in wastewater globally. Bisphenol A (BPA) is one compound belonging to this group. This work proposes the study of the employment of several metal-supported (2 wt. %) carbon nanospheres (CNS) for BPA degradation by catalytic wet-air oxidation. Several techniques were used for the catalyst characterization: thermogravimetry, X-ray diffractometry (XRD), Fourier transformed infrared spectrometry (FTIR), determination of isoelectric point, elemental analysis, X-ray fluorescence (XRF), scanning electron microscopy (SEM), and N₂ adsorption–desorption isotherms. Different loads of Ru in the catalyst were also tested for BPA degradation (1, 2, 5, 7, and 10%), being the first minimum value to achieve a conversion above 97% in 90 min 2 wt. % of Ru in the CNS-Ru catalyst. In the stability test with CNS-Ru and CNS-Pt, CNS-Pt demonstrated less activity and stability. Two potential models were proposed to adjust experimental data with CNS-Ru(2%) at different conditions of BPA initial concentration, catalyst mass, temperature, and pressure of the reaction. Both models showed a high determination coefficient (R² > 0.98). Finally, the efficiency of CNS-Ru and CNS-Pt was tested in a real hospital wastewater matrix obtaining better results the CNS-Pt(2%) catalyst. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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17 pages, 3272 KiB

Open AccessArticle

Photocatalytic Degradation of Antibiotics by Superparamagnetic Iron Oxide Nanoparticles. Tetracycline Case

by Sunday Joseph Olusegun, Gonzalo Larrea, Magdalena Osial, Krystyna Jackowska and Pawel Krysinski

Catalysts 2021, 11(10), 1243; https://doi.org/10.3390/catal11101243 - 15 Oct 2021

Cited by 45 | Viewed by 4089

Abstract

The challenges associated with the uncontrolled presence of antibiotics such as tetracycline in the environment have necessitated their removal through different techniques. Tetracycline is hard to degrade in living organisms and can even be converted to more toxic substances. In view of this, [...] Read more.

The challenges associated with the uncontrolled presence of antibiotics such as tetracycline in the environment have necessitated their removal through different techniques. Tetracycline is hard to degrade in living organisms and can even be converted to more toxic substances. In view of this, we synthesized iron oxide nanoparticles with good magnetization (70 emu g⁻¹) and 15 nm particle size for the adsorption and photocatalytic degradation of tetracycline. Characterization carried out on the synthesized iron oxides revealed a bandgap of 1.83 eV and an isoelectric point at pH 6.8. The results also showed that the pH of the solution does not directly influence the adsorption of tetracycline. The adsorption isotherm was consistent with the model proposed by Langmuir, having 97 mg g⁻¹ adsorption capacity. Combined with the superparamagnetic behavior, this capacity is advantageous for the magnetic extraction of tetracycline from wastewater. The mechanisms of adsorption were proposed to be hydrogen bonding and n-π interactions. Photocatalytic degradation studies showed that approximately 40% of tetracycline degraded within 60 min of irradiation time with UV/vis light. The kinetics of photodegradation of tetracycline followed the pseudo-first-order mechanism, proceeding through hydroxyl radicals generated under illumination. Moreover, the photogenerated hydrogen peroxide could lead to heterogeneous photo-Fenton processes on the surface of iron oxide nanoparticles, additionally generating hydroxyl and hydroperoxyl radicals and facilitating photodegradation of tetracycline. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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20 pages, 4326 KiB

Open AccessArticle

A Comprehensive Assessment of Catalytic Performances of Mn₂O₃ Nanoparticles for Peroxymonosulfate Activation during Bisphenol A Degradation

by Li Chen, Wanyi Fu, Congyu Hou, Yulong Yang and Xihui Zhang

Catalysts 2021, 11(8), 993; https://doi.org/10.3390/catal11080993 - 18 Aug 2021

Cited by 13 | Viewed by 3384

Abstract

Catalytic performances of Mn₂O₃ nanoparticles for peroxymonosulfate (PMS) activation in bisphenol A (BPA) degradation were comprehensively investigated in this study. Experimental results showed that 10 mg/L BPA could be 100% degraded within 20 min with the dosages of 0.2 g/L [...] Read more.

Catalytic performances of Mn₂O₃ nanoparticles for peroxymonosulfate (PMS) activation in bisphenol A (BPA) degradation were comprehensively investigated in this study. Experimental results showed that 10 mg/L BPA could be 100% degraded within 20 min with the dosages of 0.2 g/L Mn₂O₃ and 0.1 mM PMS. Moreover, Mn₂O₃ showed remarkable activity in activation of PMS and excellent adaptability in various real water matrices, including river water, tap water and secondary effluents. Based on the radical detection and scavenging experiments, it was found that both radical and non-radical oxidation contributed to the degradation of BPA and ¹O₂ was the dominant species in the degradation compared to ^•OH, SO₄^•− and O₂^•−. A total of 15 transformation products were identified by LC/MS-MS during BPA degradation in the Mn₂O₃/PMS system, and degradation pathways via three routes are proposed. Compared with lab-made catalysts reported in the literature, the Mn₂O₃ catalyst demonstrated its superiority in terms of its high TOC removal, low PMS consumption and fast degradation rate for BPA. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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20 pages, 4399 KiB

Open AccessFeature PaperArticle

Magnetite-Based Catalyst in the Catalytic Wet Peroxide Oxidation for Different Aqueous Matrices Spiked with Naproxen–Diclofenac Mixture

by Ysabel Huaccallo-Aguilar, Silvia Álvarez-Torrellas, Johanny Martínez-Nieves, Jonathan Delgado-Adámez, María Victoria Gil, Gabriel Ovejero and Juan García

Catalysts 2021, 11(4), 514; https://doi.org/10.3390/catal11040514 - 19 Apr 2021

Cited by 12 | Viewed by 2675

Abstract

Magnetite supported on multiwalled carbon nanotubes catalysts were synthesized by co-precipitation and hydrothermal treatment. The magnetic catalysts were characterized by X-ray diffraction, Fourier-transform infrared spectrometry, thermogravimetric analysis and N2 physisorption. The catalysts were then tested for their ability to remove diclofenac (DCF) and [...] Read more.

Magnetite supported on multiwalled carbon nanotubes catalysts were synthesized by co-precipitation and hydrothermal treatment. The magnetic catalysts were characterized by X-ray diffraction, Fourier-transform infrared spectrometry, thermogravimetric analysis and N2 physisorption. The catalysts were then tested for their ability to remove diclofenac (DCF) and naproxen (NAP) from an aqueous solution at different conditions (pH, temperature, and hydrogen peroxide) to determine the optimum conditions for chemical oxidation. The optimization of the process parameters was conducted using response surface methodology (RSM) coupled with Box–Behnken design (BBD). By RSM–BBD methodology, the optimal parameters (1.75 mM H₂O₂ dosage, 70 °C and pH 6.5) were determined, and the removal percentages of NAP and DCF were 19 and 54%, respectively. The NAP–DCF degradation by catalytic wet peroxide oxidation (CWPO) was caused by •OH radicals. In CWPO of mixed drug solutions, DCF and NAP showed competitive oxidation. Hydrophobic interactions played an important role during the CWPO process. On the other hand, the magnetic catalyst reduced its activity after the second cycle of reuse. In addition, proof of concept and disinfection tests performed at the operating conditions showed results following the complexity of the water matrices. In this sense, the magnetic catalyst in CWPO has adequate potential to treat water contaminated with NAP–DCF mixtures. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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17 pages, 1836 KiB

Open AccessFeature PaperArticle

Metal-Loaded Mesoporous MCM-41 for the Catalytic Wet Peroxide Oxidation (CWPO) of Acetaminophen

by Mohammed Hachemaoui, Carmen B. Molina, Carolina Belver, Jorge Bedia, Adel Mokhtar, Rachida Hamacha and Bouhadjar Boukoussa

Catalysts 2021, 11(2), 219; https://doi.org/10.3390/catal11020219 - 7 Feb 2021

Cited by 34 | Viewed by 3199

Abstract

MCM-41 based catalysts (molar ratio Si/Al = 40) were prepared by a hydrothermal route, modified by ionic exchange with different metals (Cu, Cr, Fe and Zn) and finally calcined at 550 °C. The catalysts were fully characterized by different techniques that confirmed the [...] Read more.

MCM-41 based catalysts (molar ratio Si/Al = 40) were prepared by a hydrothermal route, modified by ionic exchange with different metals (Cu, Cr, Fe and Zn) and finally calcined at 550 °C. The catalysts were fully characterized by different techniques that confirmed the formation of oxides of the different metals on the surfaces of all materials. Low-angle X-ray diffraction (XRD) analyses showed that calcination resulted in the incorporation of metallic Zn, Fe and Cr in the framework of MCM-41, while in the case of Cu, thin layers of CuO were formed on the surface of MCM-41. The solids obtained were tested in the catalytic wet peroxide oxidation (CWPO) of acetaminophen at different temperatures (25–55 °C). The activity followed the order: Cr/MCM-41 ≥ Fe/MCM-41 > Cu/MCM-41 > Zn/MCM-41. The increase of the reaction temperature improved the performance and activity of Cr/MCM-41 and Fe/MCM-41 catalysts, which achieved complete conversion of acetaminophen in short reaction times (15 min in the case of Cr/MCM-41). Fe/MCM-41 and Cr/MCM-41 were submitted to long-term experiments, being the Fe/MCM-41 catalyst the most stable with a very low metal leaching. The leaching results were better than those previously reported in the literature, confirming the high stability of Fe/MCM-41 catalysts synthesized in this study. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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14 pages, 2322 KiB

Open AccessFeature PaperArticle

Screening of Activated Carbons for the Treatment of Highly Concentrated Phenol Solutions Using Catalytic Wet Peroxide Oxidation: The Effect of Iron Impurities on the Catalytic Activity

by Maria T. Pinho, Rui S. Ribeiro, Helder T. Gomes, Joaquim L. Faria and Adrián M. T. Silva

Catalysts 2020, 10(11), 1318; https://doi.org/10.3390/catal10111318 - 13 Nov 2020

Cited by 6 | Viewed by 2308

Abstract

Activated carbons (ACs) have been used as metal supports for catalytic wet peroxide oxidation (CWPO) of organic compounds. A shortcoming is that added metals can undergo leaching, leading to catalyst deactivation and secondary contamination of the treated water. In the present study, CWPO [...] Read more.

Activated carbons (ACs) have been used as metal supports for catalytic wet peroxide oxidation (CWPO) of organic compounds. A shortcoming is that added metals can undergo leaching, leading to catalyst deactivation and secondary contamination of the treated water. In the present study, CWPO of phenol aqueous solutions was investigated in the presence of five commercial ACs without added metals yet containing different extents of iron impurities resulting from their industrial preparation procedures (ROX 0.8, RX 3-Extra, C-Gran and PK 0.25-1 from Cabot Norit and HYDRAFFIN AS 12/450 from Degussa). Application of as-received ROX 0.8 leads to the best compromise between removals of phenol (79%) and total organic carbon (TOC; 50%) and iron leaching (0.22 mg L⁻¹). In-house-modified ROX 0.8 materials, obtained by thermal treatment under inert atmosphere followed by activation under oxidative atmosphere, were also tested. The activity of ROX 0.8 oxidized at 673 K (ROXN₆₇₃) was the highest among these materials (92% and 57% of phenol and TOC removals, respectively) and with iron leaching (0.67 mg L⁻¹) well below the limits established by European regulations for discharge of treated waters. This enhanced performance was mainly explained by the more developed porous structure and higher specific surface area (S_BET) of ROXN₆₇₃, thus promoting better accessibility to iron impurities, which act as active sites for CWPO at the surface of the catalyst. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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14 pages, 2877 KiB

Open AccessArticle

Enhanced Photocatalytic Degradation of Caffeine Using Titanium Dioxide Photocatalyst Immobilized on Circular Glass Sheets under Ultraviolet C Irradiation

by Rattana Muangmora, Patiya Kemacheevakul, Patiparn Punyapalakul and Surawut Chuangchote

Catalysts 2020, 10(9), 964; https://doi.org/10.3390/catal10090964 - 22 Aug 2020

Cited by 16 | Viewed by 3368

Abstract

This work presents the development of titanium dioxide (TiO₂) film immobilized on circular glass sheets for photocatalytic degradation of caffeine under ultraviolet C (UVC) irradiation. TiO₂ was synthesized through the ultrasonic-assisted sol–gel method and immobilized on circular glass sheets by [...] Read more.

This work presents the development of titanium dioxide (TiO₂) film immobilized on circular glass sheets for photocatalytic degradation of caffeine under ultraviolet C (UVC) irradiation. TiO₂ was synthesized through the ultrasonic-assisted sol–gel method and immobilized on circular glass sheets by the doctor blade technique. Polyvinylpyrrolidone (PVP) was used to mix with the TiO₂ precursor solution to enhance film adhesion on the glass surface. TiO₂ film was mainly composed of anatase phase with a small amount of rutile phase. Caffeine removal was found to increase with increasing irradiation time. Caffeine (20 mg/L) in the synthetic wastewater could not be detected after 3 h of UVC irradiation. The reaction rate of caffeine degradation followed the pseudo-first-order model. The concentrated caffeine solutions required a longer irradiation time for degradation. The used TiO₂-coated glass sheets could be easily separated from the treated wastewater and reusable. The caffeine removal efficiency of TiO₂-coated glass sheets in each cycle maintained a high level (~100%) during fifteen consecutive cycles. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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9 pages, 1745 KiB

Open AccessArticle

Detoxification of Cylindrospermopsin by Pyrite in Water

by Shulian Wang, Yongmei Chen, Yiying Jiao and Zhu Li

Catalysts 2019, 9(9), 699; https://doi.org/10.3390/catal9090699 - 21 Aug 2019

Cited by 3 | Viewed by 2740

Abstract

Cylindrospermopsin (CYN) is a cyanobacterial toxin released from eutrophic water. It persistently remains in the environment because its degradation under solar light is extremely low. In this study, pyrite, an abundant mineral, was investigated as a catalyst for decomposing and detoxifying CYN in [...] Read more.

Cylindrospermopsin (CYN) is a cyanobacterial toxin released from eutrophic water. It persistently remains in the environment because its degradation under solar light is extremely low. In this study, pyrite, an abundant mineral, was investigated as a catalyst for decomposing and detoxifying CYN in water. A detailed examination of intermediates provided insights into the degradation pathway. Electron spin resonance spectra revealed that H₂O₂ and hydroxyl radicals (^•OH) were generated at the pyrite surface while promoting the recycling of Fe(III) into Fe(II) during the degradation process. This degradation system could be uniquely efficient in the presence of relatively high levels of natural organic matter because the structure of the uracil ring is decomposed to detoxify CYN. This work confirms a new approach to selectively and effectively detoxifying CYN in water using an inexpensive, environmentally friendly, and bio-compatible mineral. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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15 pages, 2693 KiB

Open AccessArticle

An External Energy Independent WO₃/MoCl₅ Nano-Sized Catalyst for the Superior Degradation of Crystal Violet and Rhodamine B Dye

by Dongin Kim, Geonwoo Kim, Hyeonbin Bae, Eunwoo Kim, Byunghyun Moon, Daho Cheon and Naresh Hiralal Tarte

Catalysts 2019, 9(8), 642; https://doi.org/10.3390/catal9080642 - 27 Jul 2019

Cited by 9 | Viewed by 3747

Abstract

In this study, the synthesis of a novel catalyst WO₃/MoCl₅ was carried out by the thermal method. The method gave an entirely different product compared to previous studies that doped Mo on the surface of semiconductor metal oxides. The degradation [...] Read more.

In this study, the synthesis of a novel catalyst WO₃/MoCl₅ was carried out by the thermal method. The method gave an entirely different product compared to previous studies that doped Mo on the surface of semiconductor metal oxides. The degradation reaction of crystal violet (CV) and rhodamine B (RB) dye were done without any energy source. The results showed an incomparably superior result for degradation, with a reaction rate constant of 1.74 s⁻¹ for 30 ppm CV, 1.08 s⁻¹ for 30 ppm RB, and a higher value than 1 s⁻¹ for both cases of 50 ppm dye solution. To the author’s knowledge, this catalyst has the highest reaction rate compared to other studies that targeted CV and RB, with an immense reaction rate increase of more than 100 times. Reusability of the three trials was verified, and the only process required was washing the catalyst after the reaction. One of the drawbacks of the advanced oxidation process (AOP), which has a degradation percent limit, has been solved, since 100% mineralization of the dye was available using this catalyst. FT-IR spectroscopy revealed that W-O-Mo linkage was successfully processed while Mo-Cl linkage has retained. ¹H-NMR spectroscopy results confirmed that the degradation product of the dye treated by simple MoCl₅ and WO₃/MoCl₅ was different. Deep inspection of specific regions of NMR fields gave necessary information about the degradation product using WO₃/MoCl₅. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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13 pages, 6231 KiB

Open AccessArticle

Modified Nimo Nanoparticles for Efficient Catalytic Hydrogen Generation from Hydrous Hydrazine

by Ying Liu, Huan Zhang, Cong Ma and Nan Sun

Catalysts 2019, 9(7), 596; https://doi.org/10.3390/catal9070596 - 10 Jul 2019

Cited by 7 | Viewed by 3530

Abstract

Precious metal-free NiMoM (M = Pr₂O₃, Cu₂O) catalysts have been synthesized through a simple coreduction method, without any surfactant or support material, and characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). [...] Read more.

Precious metal-free NiMoM (M = Pr₂O₃, Cu₂O) catalysts have been synthesized through a simple coreduction method, without any surfactant or support material, and characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The resultant Pr₂O₃- or Cu₂O-modified NiMo catalysts exhibit different structures, which is due to a difference in the synergistic effects of NiMo and the modifying elements. NiMoPr₂O₃ has an amorphous structure, with low crystallinity and uniform particle dispersion, while NiMo@Cu₂O adopts the core–shell structure, where the core and shell are synergistic with each other to promote electron transfer efficiency. The support material-free nanocatalysts Ni₉Mo₁(Pr₂O₃)_0.375 and Ni₄Mo@Cu₂O are both highly efficient compared with bimetallic NiMo catalysts, in terms of hydrogen generation from hydrous hydrazine (N₂H₄·H₂O) at 343 K, with total turnover frequencies (TOFs) of 62 h⁻¹ and 71.4 h⁻¹, respectively. Their corresponding activation energies (Ea) were determined to be 43.24 kJ mol⁻¹ and 46.47 kJ mol⁻¹, respectively. This is the first report on the use of Pr-modified NiMo and core–shell NiMo@Cu₂O catalysts, and these results may be used to promote the effective application of noble metal-free nanocatalysts for hydrogen production from hydrous hydrazine. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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19 pages, 4934 KiB

Open AccessArticle

Effect of Surface Chemistry and Crystallographic Parameters of TiO₂ Anatase Nanocrystals on Photocatalytic Degradation of Bisphenol A

by Gregor Žerjav, Albin Pintar, Michael Ferentz, Miron Landau, Anat Haimovich, Amir Goldbourt and Moti Herskowitz

Catalysts 2019, 9(5), 447; https://doi.org/10.3390/catal9050447 - 14 May 2019

Cited by 8 | Viewed by 3593

Abstract

The photocatalytic activity of a series of anatase TiO₂ materials with different amounts of exposed (001) facets (i.e., 12% (TiO₂-1), 38% (TiO₂-3), and 63% (TiO₂-3)) was tested in a batch slurry reactor towards liquid-phase bisphenol A [...] Read more.

The photocatalytic activity of a series of anatase TiO₂ materials with different amounts of exposed (001) facets (i.e., 12% (TiO₂-1), 38% (TiO₂-3), and 63% (TiO₂-3)) was tested in a batch slurry reactor towards liquid-phase bisphenol A (BPA, c₀(BPA) = 10 mg/L, c_cat. = 125 mg/L) degradation. Photo-electrochemical and photo-luminescence measurements revealed that with the increasing amount of exposed anatase (001) facets, the catalysts generate more electron-hole pairs and OH∙ radicals that participate in the photocatalytic mineralization of pollutants dissolved in water. In the initial stages of BPA degradation, a correlation between % exposure of (001) facets and catalytic activity was developed, which was in good agreement with the findings of the photo-electrochemical and photo-luminescence measurements. TiO₂-1 and TiO₂-3 solids achieved 100% BPA removal after 80 min in comparison to the TiO₂-2 sample. Adsorption of BPA degradation products onto the TiO₂-2 catalyst surface was found to have a detrimental effect on the photocatalytic performance in the last stage of the reaction course. Consequently, the global extent of BPA mineralization decreased with the increasing exposure of anatase (001) facets. The major contribution to the enhanced reactivity of TiO₂ anatase (001) surface is the Brønsted acidity resulting from dissociative chemisorption of water on a surface as indicated by FTIR, TPD, and MAS NMR analyses. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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23 pages, 4024 KiB

Open AccessFeature PaperArticle

Optimization Parameters, Kinetics, and Mechanism of Naproxen Removal by Catalytic Wet Peroxide Oxidation with a Hybrid Iron-Based Magnetic Catalyst

by Ysabel Huaccallo-Aguilar, Silvia Álvarez-Torrellas, Marcos Larriba, V. Ismael Águeda, José Antonio Delgado, Gabriel Ovejero and Juan García

Catalysts 2019, 9(3), 287; https://doi.org/10.3390/catal9030287 - 20 Mar 2019

Cited by 21 | Viewed by 4631

Abstract

This work presents a study of the assessment of the operating parameters of the catalytic wet peroxide oxidation (CWPO) of naproxen (NAP) using magnetite/multi-walled carbon nanotubes (Fe₃O₄/MWCNTs) as a catalyst. The effect of pH, temperature, and H₂O [...] Read more.

This work presents a study of the assessment of the operating parameters of the catalytic wet peroxide oxidation (CWPO) of naproxen (NAP) using magnetite/multi-walled carbon nanotubes (Fe₃O₄/MWCNTs) as a catalyst. The effect of pH, temperature, and H₂O₂ dosage on CWPO process was evaluated by using the response surface model (RSM), allowing us to obtain an optimum NAP removal of 82% at the following operating conditions: pH = 5, T = 70 °C, [H₂O₂]₀ = 1.5 mM, and [NAP]₀ = 10.0 mg/L. Therefore, NAP degradation kinetics were revealed to follow a pseudo-second-order kinetic model, and an activation energy value of 4.75 kJ/mol was determined. Adsorption and using only H₂O₂ experiments, both considered as blank tests, showed no significant removal of the pollutant. Moreover, Fe₃O₄/MWCNTs material exhibited good recyclability along three consecutive cycles, finding an average NAP removal percentage close to 80% in each cycle of 3 h reaction time. In addition, the scavenging tests confirmed that the degradation of NAP was mainly governed by ^•OH radicals attack. Two reaction sequences were proposed for the degradation mechanism according to the detected byproducts. Finally, the versatility of the catalyst was evidenced in the treatment of different environmentally relevant aqueous matrices (wastewater treatment plant effluent (WWTP), surface water (SW), and a hospital wastewater (HW)) spiked with NAP, obtaining total organic carbon (TOC) removal efficiencies after 8 h in the following order: NAP-SW > NAP-HW > NAP-WWTP. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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