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Journal ArticleDOI

Enhanced photocatalytic degradation of methylene blue and methyl orange by ZnO:Eu nanoparticles

TL;DR: In this paper, the influence of europium doping and solvents on size, particles agglomeration, light absorption and photocatalytic activity was analyzed in ZnO nanoparticles.
Abstract: ZnO nanoparticles doped with different Eu3+ percentages were synthesized in water (ZnO:Eu(x%)-W) and other solvents (methanol ZnO:Eu(x%)-M and ethanol ZnO:Eu(x%)-E). X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), optical absorption and photoluminescence (PL) spectroscopy were used for characterization of the nanoparticles. Our results showed influence of europium doping and solvents on size, particles agglomeration, light absorption and photocatalytic activity. Improvement in photocatalytical activity with addition of Eu3+ doping was detected. Particle size increased with Eu3+ doping in water samples, while it decreased in methanol. Agglomeration was more prominent in ZnO:Eu(x%)-W samples. Greater amount of surface OH groups in case of ZnO:Eu(x%)-M samples was detected by PL, XPS and FTIR measurements. Influence of europium doping, as an electron trap, and surface OH groups, as a hole trap, was studied in sunlight photocatalytic degradation of cationic methylene blue (MB) and anionic methyl orange (MO). Improved photocatalytic behavior was discussed and influence of active species was further investigated using hole and hydroxyle radical scavengers. The degradation pathway of MB and MO, using high performance liquid chromatohraphy (HPLC), is also examined.

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Citations
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Journal ArticleDOI
TL;DR: In this article, a comprehensive review discusses the pseudo kinetics and mechanisms of the photodegradation reactions, as well as the operational factors that govern the adsorption of dye molecules, including the initial dye concentration, pH of the solution, temperature of the reaction medium, and light intensity.
Abstract: Due to its low cost, environmentally friendly process, and lack of secondary contamination, the photodegradation of dyes is regarded as a promising technology for industrial wastewater treatment. This technology demonstrates the light-enhanced generation of charge carriers and reactive radicals that non-selectively degrade various organic dyes into water, CO2, and other organic compounds via direct photodegradation or a sensitization-mediated degradation process. The overall efficiency of the photocatalysis system is closely dependent upon operational parameters that govern the adsorption and photodegradation of dye molecules, including the initial dye concentration, pH of the solution, temperature of the reaction medium, and light intensity. Additionally, the charge-carrier properties of the photocatalyst strongly affect the generation of reactive species in the heterogeneous photodegradation and thereby dictate the photodegradation efficiency. Herein, this comprehensive review discusses the pseudo kinetics and mechanisms of the photodegradation reactions. The operational factors affecting the photodegradation of either cationic or anionic dye molecules, as well as the charge-carrier properties of the photocatalyst, are also fully explored. By further analyzing past works to clarify key active species for photodegradation reactions and optimal conditions, this review provides helpful guidelines that can be applied to foster the development of efficient photodegradation systems.

464 citations


Cites background from "Enhanced photocatalytic degradation..."

  • ...This photodegradation of dye molecules via the photosensitization process was reported in the cationic new fuchsin/graphene quantum dots [114], RhB/Zn-doped BiOBr [115], MB and MO/Eu3+-doped ZnO [116], and RhB/Nb2O5 [117] systems....

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Journal ArticleDOI
TL;DR: In this paper, the authors reviewed the recent advancements in photocatalysis for dye degradation in industrial effluents by categorizing photocatalyst materials into three generations: first generation photocatalysts are composed of single-component materials (e.g., TiO2, ZnO, and CdS), while second generation photochemical degradation materials are made up of multiple components in a suspension (i.e., WO3/NiWO4, BiOI/ZnTiO3 and C3N4/Ag3VO4).
Abstract: Discharging dye contaminants into water is a major concern around the world. Among a variety of methods to treat dye-contaminated water, photocatalytic degradation has gained attention as a tool for treating the colored water. Herein, we review the recent advancements in photocatalysis for dye degradation in industrial effluents by categorizing photocatalyst materials into three generations. First generation photocatalysts are composed of single-component materials (e.g., TiO2, ZnO, and CdS), while second generation photocatalysts are composed of multiple components in a suspension (e.g., WO3/NiWO4, BiOI/ZnTiO3, and C3N4/Ag3VO4). Photocatalysts immobilized on solid substrates are regarded as third generation materials (e.g., FTO/WO3-ZnO, Steel/TiO2-WO3, and Glass/P-TiO2). Photocatalytic degradation mechanisms, factors affecting the dye degradation, and the lesser-debated uncertainties related to the photocatalysis are also discussed to offer better insights into environmental applications. Furthermore, quantum yields of different photocatalysts are calculated, and a performance evaluation method is proposed to compare photocatalyst systems for dye degradation. Finally, we discuss the present limitations of photocatalytic dye degradation for field applications and the future of the technology.

371 citations

Journal ArticleDOI
TL;DR: In this article, a facile sol-gel method was used to enhance degradation of single and binary methylene blue and methyl orange by ultraviolet photocatalysis, and the results showed that the prepared materials were easier to separate from the treated liquid using a simple sedimentation or filtration method than P25 TiO2.

363 citations

Journal ArticleDOI
14 Jan 2022-Water
TL;DR: In this paper , the authors provided a tutorial basis for the readers working in the dye degradation research area and provided a wide range of previously published work on advanced photocatalytic systems.
Abstract: The unavailability of clean drinking water is one of the significant health issues in modern times. Industrial dyes are one of the dominant chemicals that make water unfit for drinking. Among these dyes, methylene blue (MB) is toxic, carcinogenic, and non-biodegradable and can cause a severe threat to human health and environmental safety. It is usually released in natural water sources, which becomes a health threat to human beings and living organisms. Hence, there is a need to develop an environmentally friendly, efficient technology for removing MB from wastewater. Photodegradation is an advanced oxidation process widely used for MB removal. It has the advantages of complete mineralization of dye into simple and nontoxic species with the potential to decrease the processing cost. This review provides a tutorial basis for the readers working in the dye degradation research area. We not only covered the basic principles of the process but also provided a wide range of previously published work on advanced photocatalytic systems (single-component and multi-component photocatalysts). Our study has focused on critical parameters that can affect the photodegradation rate of MB, such as photocatalyst type and loading, irradiation reaction time, pH of reaction media, initial concentration of dye, radical scavengers and oxidising agents. The photodegradation mechanism, reaction pathways, intermediate products, and final products of MB are also summarized. An overview of the future perspectives to utilize MB at an industrial scale is also provided. This paper identifies strategies for the development of effective MB photodegradation systems.

234 citations

Journal ArticleDOI
01 Dec 2020
TL;DR: In this paper, a new validation method was proposed and was then employed to re-examine previously published adsorption kinetic data to eliminate modeling biasness and eliminate model validation tools that cannot provide any kind of certainty on the validity of a model.
Abstract: Adsorption for water and wastewater treatment has been the subject of many research in the scientific community, focusing mainly on either equilibrium or kinetic studies. Adsorption kinetics are commonly modeled using pseudo-first and pseudo-second order rate laws. Analyses of published works in the past two decades indicated that the pseudo-second order is considered to be the superior model as it can represent many adsorption systems. However, critical assessment of modeling techniques and practices suggests that its superiority could be a consequence of currently acceptable modeling norms which tend to favor the pseudo-second order model. The partiality was due to several modeling pitfalls that are often neglected. In addition, commonly used model validation tools are often used haphazardly and redundantly. As such, they cannot sufficiently provide any kind of certainty on the validity of a model. To eliminate modeling biasness, a new validation method was proposed and was then employed to re-examine previously published adsorption kinetic data.

208 citations

References
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01 Jan 1995

14,960 citations

Journal ArticleDOI
TL;DR: In this paper, a literature review of the use of sorbents and biosorbents to treat polluted aqueous effluents containing dyes:organics or metal ions has been conducted.

13,746 citations

Book
18 Jun 2004
TL;DR: This new edition of this highly successful manual is not only a revised text but has been extended to meet the interpretive needs of Raman users as well as those working in the IR region, creating a uniquely practical, comprehensive and detailed source for spectral interpretation.
Abstract: The third edition of this highly successful manual is not only a revised text but has been extended to meet the interpretive needs of Raman users as well as those working in the IR region. The result is a uniquely practical, comprehensive and detailed source for spectral interpretation. Combining in one volume, the correlation charts and tables for spectral interpretation for these two complementary techniques, this book will be of great benefit to those using or considering either technique.In addition to the new Raman coverage the new edition offers:* new section on macromolecules including synthetic polymers and biomolecules;* expansion of the section on NIR (near infrared region) to reflect recent growth in this area;* extended chapter on inorganic compounds including minerals and glasses;* redrawn and updated charts plus a number of new charts covering data new to this edition.This new edition will be invaluable in every industrial, university, government and hospital laboratory where infrared (FT-IR) and Raman spectral data need to be analysed.

6,428 citations

Journal ArticleDOI
TL;DR: An overview of second-order kinetic expressions is described in this paper based on the solid adsorption capacity, which shows that a pseudo-second-order rate expression has been widely applied to the Adsorption of pollutants from aqueous solutions onto adsorbents.

3,458 citations

Book
30 Jul 2004
TL;DR: In this paper, the authors present a set of techniques for detecting anomalous infrared spectra, including Fourier Transform Infrared Spectrometers (FTIS) and Spectral Spectral Transform Transform (STT) this paper.
Abstract: Series Preface.Preface.Acronyms, Abbreviations and Symbols.About the Author.1. Introduction.1.1 Electromagnetic Radiation.1.2 Infrared Absorptions.1.3 Normal Modes of Vibration.1.4 Complicating Factors.1.4.1 Overtone and Combination Bands.1.4.2 Fermi Resonance.1.4.3 Coupling.1.4.4 Vibration-Rotation Bands.References.2. Experimental Methods.2.1 Introduction.2.2 Dispersive Infrared Spectrometers.2.3 Fourier-Transform Infrared Spectrometers.2.3.1 Michelson Interferometers.2.3.2 Sources and Detectors.2.3.3 Fourier-Transformation.2.3.4 Moving Mirrors.2.3.5 Signal-Averaging.2.3.6 Advantages.2.3.7 Computers.2.3.8 Spectra.2.4 Transmission Methods.2.4.1 Liquids and Solutions.2.4.2 Solids.2.4.3 Gases.2.4.4 Pathlength Calibration.2.5 Reflectance Methods.2.5.1 Attenuated Total Reflectance Spectroscopy.2.5.2 Specular Reflectance Spectroscopy.2.5.3 Diffuse Reflectance Spectroscopy.2.5.4 Photoacoustic Spectroscopy.2.6 Microsampling Methods.2.7 Chromatography-Infrared Spectroscopy.2.8 Thermal Analysis-Infrared Spectroscopy.2.9 Other Techniques.References.3. Spectral Analysis.3.1 Introduction.3.2 Group Frequencies.3.2.1 Mid-Infrared Region.3.2.2 Near-Infrared Region.3.2.3 Far-Infrared Region.3.3 Identification.3.4 Hydrogen Bonding.3.5 Spectrum Manipulation.3.5.1 Baseline Correction.3.5.2 Smoothing.3.5.3 Difference Spectra.3.5.4 Derivatives.3.5.5 Deconvolution.3.5.6 Curve-Fitting.3.6 Concentration.3.7 Simple Quantitative Analysis.3.7.1 Analysis of Liquid Samples.3.7.2 Analysis of Solid Samples.3.8 Multi-Component Analysis.3.9 Calibration Methods.References.4. Organic Molecules.4.1 Introduction.4.2 Aliphatic Hydrocarbons.4.3 Aromatic Compounds.4.4 Oxygen-Containing Compounds.4.4.1 Alcohols and Phenols.4.4.2 Ethers.4.4.3 Aldehydes and Ketones.4.4.4 Esters.4.4.5 Carboxylic Acids and Anhydrides.4.5 Nitrogen-Containing Compounds.4.5.1 Amines.4.5.2 Amides.4.6 Halogen-Containing Compounds.4.7 Heterocyclic Compounds.4.8 Boron Compounds.4.9 Silicon Compounds.4.10 Phosphorus Compounds.4.11 Sulfur Compounds.4.12 Near-Infrared Spectra.4.13 Identification.References.5. Inorganic Molecules.5.1 Introduction.5.2 General Considerations.5.3 Normal Modes of Vibration.5.4 Coordination Compounds.5.5 Isomerism.5.6 Metal Carbonyls.5.7 Organometallic Compounds.5.8 Minerals.References.6. Polymers.6.1 Introduction.6.2 Identification.6.3 Polymerization.6.4 Structure.6.5 Surfaces.6.6 Degradation.References.7. Biological Applications.7.1 Introduction.7.2 Lipids.7.3 Proteins and Peptides.7.4 Nucleic Acids.7.5 Disease Diagnosis.7.6 Microbial Cells.7.7 Plants.7.8 Clinical Chemistry.References.8. Industrial and Environmental Applications.8.1 Introduction.8.2 Pharmaceutical Applications.8.3 Food Science.8.4 Agricultural Applications.8.5 Pulp and Paper Industries.8.6 Paint Industry.8.7 Environmental Applications.References.Responses to Self-Assessment Questions.Bibliography.Glossary of Terms.SI Units and Physical Constants.Periodic Table.Index.

2,802 citations