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22 pages, 3363 KiB

Open AccessFeature PaperArticle

Modeling of Degradation of Diazo Dye in Swirl-Flow Photocatalytic Reactor: Response Surface Approach

by Waleed Jadaa, Anand Prakash and Ajay K. Ray

Catalysts 2020, 10(12), 1418; https://doi.org/10.3390/catal10121418 - 4 Dec 2020

Cited by 5 | Viewed by 2290

Photocatalytic degradation of Direct Blue 15 (DB15), an azo dye, was studied using a swirl-flow monolithic reactor under UV irradiation. The degradation reactions were carried out to investigate effects of initial dye concentration, catalyst loading, and light intensity at an optimal pH. The [...] Read more.

Photocatalytic degradation of Direct Blue 15 (DB15), an azo dye, was studied using a swirl-flow monolithic reactor under UV irradiation. The degradation reactions were carried out to investigate effects of initial dye concentration, catalyst loading, and light intensity at an optimal pH. The experiments were designed and mathematically modelled by CCD-RSM (central composite design-response surface methodology) approach. It was found that the selected parameters significantly affect DB15 degradation. In terms of the linear term, catalyst loading and light intensity had a synergistic effect, while dye concentration registered the opposite effect. Strong interaction was observed between catalyst loading and both light intensity and initial dye concentration compared with the interaction of light intensity and initial dye concentration. Based on the experimental results, a quadratic model was developed to predict the percentage removal of DB15. The predicted values of the model were in good agreement with the experimental values (R² = 0.987), indicating the model fits well for the parameter space for which experiments were performed. According to diagnostic plots, the model credibility was valid because its residuals were distributed normally and exhibited a random pattern based on their examination versus the predicted values. The results revealed that the initial dye concentration and catalyst concentration have a significant effect on the mineralization time. Full article

(This article belongs to the Special Issue State-of-the-Art Photocatalytical Technology in North America)

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16 pages, 3324 KiB

Open AccessFeature PaperArticle

Photocatalytic Activity of Aeroxide TiO₂ Sensitized by Natural Dye Extracted from Mangosteen Peel

by Malini Ghosh, Pankaj Chowdhury and Ajay K. Ray

Catalysts 2020, 10(8), 917; https://doi.org/10.3390/catal10080917 - 10 Aug 2020

Cited by 13 | Viewed by 4212

Abstract

Natural dye sensitizers are environment-friendly and inexpensive substances that could be used for photocatalytic decontamination of organic pollutants. In this study, a natural dye extracted from mangosteen peel, containing a significant amount of anthocyanin dye, has been successfully employed to sensitize aeroxide TiO [...] Read more.

Natural dye sensitizers are environment-friendly and inexpensive substances that could be used for photocatalytic decontamination of organic pollutants. In this study, a natural dye extracted from mangosteen peel, containing a significant amount of anthocyanin dye, has been successfully employed to sensitize aeroxide TiO₂ to lower its bandgap, thereby making the process visible sunlight-driven. We have demonstrated the photocatalytic activity of mangosteen dye-sensitized-TiO₂ (MS-TiO₂) under visible solar light by studying the degradation of methylene blue (MB), a well-studied model compound. A multivariate parametric study was performed using factorial design methodology with three factors—pH, MS-TiO₂ dosage, and visible light intensity. The study indicated that pH and MS-TiO₂ dosage are the two most dominant factors for MB degradation under visible solar light. The kinetic rate constant and adsorption equilibrium constant were determined, and a Langmuir-Hinshelwood-type equation was proposed to describe MB degradation on MS-TiO₂ under visible solar light. Apparent quantum yield was also reported for the MS-TiO₂ photocatalyst at optimum experimental conditions. Full article

(This article belongs to the Special Issue State-of-the-Art Photocatalytical Technology in North America)

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15 pages, 2893 KiB

Open AccessArticle

Passive Solar Photocatalytic Treatment of Emerging Contaminants in Water: A Field Study

by Gisoo Heydari, Cooper H. Langford and Gopal Achari

Catalysts 2019, 9(12), 1045; https://doi.org/10.3390/catal9121045 - 9 Dec 2019

Cited by 6 | Viewed by 3025

Abstract

Global economic shifts towards utilization of solar energy provides opportunities for photocatalytic technologies that can harness this abundant source of energy for treatment of organic contaminants. The majority of studies in this area have been performed under artificial light, whereas in this paper, [...] Read more.

Global economic shifts towards utilization of solar energy provides opportunities for photocatalytic technologies that can harness this abundant source of energy for treatment of organic contaminants. The majority of studies in this area have been performed under artificial light, whereas in this paper, the efficacy of passive photocatalysis was studied under sunlight. Buoyant titanium dioxide (TiO₂) coated glass spheres were used to treat 2, 4-dichlorophenoxy acetic acid (2, 4-D), methyl chlorophenoxy propionic acid (MCPP), and 3, 6-Dichloro-2-methoxy benzoic acid (Dicamba) in Killex^®, a commercially available herbicide. Furthermore, photocatalytic degradation of sulfolane and a typical naphthenic acid (cyclopentane carboxylic acid—CPA) were also tested under ambient conditions. The results showed 99.8% degradation of 2, 4-D, 100% degradation of both MCPP and Dicamba in Killex^® solution, and 97.4% degradation of sulfolane by capturing 3.18 MJ/m² solar energy. Total organic carbon (TOC) was decreased by 88% and 64% in both solutions, respectively. TOC of the aqueous solution containing 20 ppm CPA was also decreased by 78.4% with 7.8 MJ/m² energy. Despite the slow kinetics and the temporal variations of sunlight in northern latitudes, the results indicated that passive photocatalysis is a promising approach for treatment of contaminants under ambient conditions. Full article

(This article belongs to the Special Issue State-of-the-Art Photocatalytical Technology in North America)

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10 pages, 2367 KiB

Open AccessArticle

The Enzyme-Like Property and Photocatalytic Effect on α, α-Diphenyl-β-Picrylhydrazyl (DPPH) of CuPt Nanocomposite

by Tao Wen, Doudou Yan, Jie Meng, Jian Liu and Haiyan Xu

Catalysts 2019, 9(10), 813; https://doi.org/10.3390/catal9100813 - 27 Sep 2019

Cited by 2 | Viewed by 2576

Abstract

With co-reduction method, a new nanocomposite consisting of Cu and Pt (CuPt) was prepared in household. The morphology of CuPt alloy was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). The diameter of CuPt was ca. 125 nm measured by [...] Read more.

With co-reduction method, a new nanocomposite consisting of Cu and Pt (CuPt) was prepared in household. The morphology of CuPt alloy was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). The diameter of CuPt was ca. 125 nm measured by dynamic light scattering (DLS). The atom ratio of Cu to Pt was determined to be about 1.2 by energy-dispersive X-ray (EDX). Enzyme-like activities of CuPt, including peroxidase (POD)-like and ascorbic acid oxidase (AAO)-like activities were examined with UV-Vis-NIR spectrometer. The CuPt was found to interact with α, α-diphenyl-β-picrylhydrazyl (DPPH) in the presence or absence of AA. With irradiation by light emitting diode (LED) light, the photocatalysis effect of CuPt on DPPH was investigated. With the addition of histidine, it was proved that singlet oxygen had an important role in the interaction involving CuPt. The new nanocomposite and the properties suggest various potentials of application. Full article

(This article belongs to the Special Issue State-of-the-Art Photocatalytical Technology in North America)

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12 pages, 1659 KiB

Open AccessArticle

Photocatalytic Degradation of Profenofos and Triazophos Residues in the Chinese Cabbage, Brassica chinensis, Using Ce-Doped TiO₂

by Xiangying Liu, You Zhan, Zhongqin Zhang, Lang Pan, Lifeng Hu, Kailin Liu, Xuguo Zhou and Lianyang Bai

Catalysts 2019, 9(3), 294; https://doi.org/10.3390/catal9030294 - 22 Mar 2019

Cited by 25 | Viewed by 4205

Abstract

Pesticides have revolutionized the modern day of agriculture and substantially reduced crop losses. Synthetic pesticides pose a potential risk to the ecosystem and to the non-target organisms due to their persistency and bioaccumulation in the environment. In recent years, a light-mediated advanced oxidation [...] Read more.

Pesticides have revolutionized the modern day of agriculture and substantially reduced crop losses. Synthetic pesticides pose a potential risk to the ecosystem and to the non-target organisms due to their persistency and bioaccumulation in the environment. In recent years, a light-mediated advanced oxidation processes (AOPs) has been adopted to resolve pesticide residue issues in the field. Among the current available semiconductors, titanium dioxide (TiO₂) is one of the most promising photocatalysts. In this study, we investigated the photocatalytic degradation of profenofos and triazophos residues in Chinese cabbage, Brassica chinensis, using a Cerium-doped nano semiconductor TiO₂ (TiO₂/Ce) under the field conditions. The results showed that the degradation efficiency of these organophosphate pesticides in B. chinensis was significantly enhanced in the presence of TiO₂/Ce. Specifically, the reactive oxygen species (ROS) contents were significantly increased in B. chinensis with TiO₂/Ce treatment, accelerating the degradation of profenofos and triazophos. Ultra-performance liquid chromatography–mass spectroscopy (UPLC-MS) analysis detected 4-bromo-2-chlorophenol and 1-phenyl-3-hydroxy-1,2,4-triazole, the major photodegradation byproducts of profenofos and triazophos, respectively. To better understand the relationship between photodegradation and the molecular structure of these organophosphate pesticides, we investigated the spatial configuration, the bond length and Mulliken atomic charge using quantum chemistry. Ab initio analysis suggests that the bonds connected by P atom of profenofos/triazophos are the initiation cleavage site for photocatalytic degradation in B. chinensis. Full article

(This article belongs to the Special Issue State-of-the-Art Photocatalytical Technology in North America)

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7 pages, 3507 KiB

Open AccessArticle

An Effective Approach to Improve the Photocatalytic Activity of Graphitic Carbon Nitride via Hydroxyl Surface Modification

by Zizhen Li, Xiangchao Meng and Zisheng Zhang

Catalysts 2019, 9(1), 17; https://doi.org/10.3390/catal9010017 - 28 Dec 2018

Cited by 17 | Viewed by 3263

Abstract

In this work, we have developed a hydrothermal method to modify g-C₃N₄ with hydroxyl surface modification. Modified g-C₃N₄ has exhibited higher photocatalytic activity in the removal of phenolic compounds under visible light. The improvement may be due [...] Read more.

In this work, we have developed a hydrothermal method to modify g-C₃N₄ with hydroxyl surface modification. Modified g-C₃N₄ has exhibited higher photocatalytic activity in the removal of phenolic compounds under visible light. The improvement may be due to the following merits: (1) Tuning of the hydrophobic surface of g-C₃N₄ to be hydrophilic; (2) improved adsorption energy, and (3) narrowed band gap for g-C₃N₄ after hydroxyl surface modification. This method is easy-to-operate, very effective in adding hydroxyl groups on the surface of C₃N₄, and may be extended to other systems to promote their photocatalytic activities in water treatment. Full article

(This article belongs to the Special Issue State-of-the-Art Photocatalytical Technology in North America)

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17 pages, 5406 KiB

Open AccessArticle

Photocatalytic Treatment of An Actual Confectionery Wastewater Using Ag/TiO₂/Fe₂O₃: Optimization of Photocatalytic Reactions Using Surface Response Methodology

by Yi Ping Lin and Mehrab Mehrvar

Catalysts 2018, 8(10), 409; https://doi.org/10.3390/catal8100409 - 21 Sep 2018

Cited by 29 | Viewed by 5286

Abstract

Titanium dioxide (TiO₂) photocatalysis is one of the most commonly studied advanced oxidation processes (AOPs) for the mineralization of deleterious and recalcitrant compounds present in wastewater as it is stable, inexpensive, and effective. Out of all, doping with metal and non-metals, [...] Read more.

Titanium dioxide (TiO₂) photocatalysis is one of the most commonly studied advanced oxidation processes (AOPs) for the mineralization of deleterious and recalcitrant compounds present in wastewater as it is stable, inexpensive, and effective. Out of all, doping with metal and non-metals, and the heterojunction with another semiconductor were proven to be efficient methods in enhancing the degradation of organic pollutants under ultraviolet (UV) and visible light. However, complex degradation processes in the treatment of an actual wastewater are difficult to model and optimize. In the present study, the application of a modified photocatalyst, Ag/TiO₂/Fe₂O₃, for the degradation of an actual confectionery wastewater was investigated. Factorial studies and statistical design of experiments using the Box-Behnken method along with response surface methodology (RSM) were employed to identify the individual and cross-factor effects of independent parameters, including light wavelength (nm), photocatalyst concentration (g/L), initial pH, and initial total organic carbon (TOC) concentration (g/L). The maximum TOC removal at optimum conditions of light wavelength (254 nm), pH (4.68), photocatalyst dosage (480 mg/L), and initial TOC concentration (11,126.5 mg/L) was determined through the numerical optimization method (9.78%) and validated with experimental data (9.42%). Finally, the first-order rate constant with respect to TOC was found to be 0.0005 min⁻¹ with a residual value of 0.998. Full article

(This article belongs to the Special Issue State-of-the-Art Photocatalytical Technology in North America)

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12 pages, 2796 KiB

Open AccessArticle

Flame-Sprayed Pure and Ce-Doped TiO₂ Photocatalysts

by Fateh Mikaeili, Selda Topcu, Gagan Jodhani and Pelagia-Irene Gouma

Catalysts 2018, 8(9), 342; https://doi.org/10.3390/catal8090342 - 22 Aug 2018

Cited by 24 | Viewed by 3823

Abstract

Pure and Ce-doped TiO₂ nanoparticles were successfully synthesized in one step by means of the scalable flame spray pyrolysis (FSP) process. Complete structural and chemical characterization of these materials revealed that the majority of the nanoparticles are crystalline and spherical, ranging from [...] Read more.

Pure and Ce-doped TiO₂ nanoparticles were successfully synthesized in one step by means of the scalable flame spray pyrolysis (FSP) process. Complete structural and chemical characterization of these materials revealed that the majority of the nanoparticles are crystalline and spherical, ranging from 5 to 45 nm in diameter. The band gap of TiO₂ was reduced by doping with Ce from 2.43 to 3.06 eV and the Ce–TiO₂ nanoparticles exhibit a strong photoelectrical response to visible light illumination. Ce–TiO₂ nanoparticles obtained with this scalable method are trivially scalable to industrial level manufacturing, granting and enabling additional approaches for the actual application of ceramic oxide nanomaterials to combat challenges such as environmental cleanup and energy production from the visible part of solar inputs. Full article

(This article belongs to the Special Issue State-of-the-Art Photocatalytical Technology in North America)

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