Catalysts

Editorial

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5 pages, 174 KiB

Open AccessEditorial

Catalytic Processes for Water and Wastewater Treatment

by John Vakros

Catalysts 2023, 13(4), 677; https://doi.org/10.3390/catal13040677 - 30 Mar 2023

Cited by 1 | Viewed by 1217

Abstract

Water and wastewater treatment still face significant challenges today [...] Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

Research

Jump to: Editorial, Review

20 pages, 4483 KiB

Open AccessArticle

Adsorption Efficiency and Photocatalytic Activity of Silver Sulfide Nanoparticles Deposited on Carbon Nanotubes

by Gururaj M. Neelgund, Sanjuana Fabiola Aguilar, Erica A. Jimenez and Ram L. Ray

Catalysts 2023, 13(3), 476; https://doi.org/10.3390/catal13030476 - 26 Feb 2023

Cited by 6 | Viewed by 1521

Abstract

A multimode, dual functional nanomaterial, CNTs-Ag₂S, comprised of carbon nanotubes (CNTs) and silver sulfide (Ag₂S) nanoparticles, was prepared through the facile hydrothermal process. Before the deposition of Ag₂S nanoparticles, hydrophobic CNTs were modified to become hydrophilic through [...] Read more.

A multimode, dual functional nanomaterial, CNTs-Ag₂S, comprised of carbon nanotubes (CNTs) and silver sulfide (Ag₂S) nanoparticles, was prepared through the facile hydrothermal process. Before the deposition of Ag₂S nanoparticles, hydrophobic CNTs were modified to become hydrophilic through refluxing with a mixture of concentrated nitric and sulfuric acids. The oxidized CNTs were employed to deposit the Ag₂S nanoparticles for their efficient immobilization and homogenous distribution. The CNTs-Ag₂S could adsorb toxic Cd(II) and completely degrade the hazardous Alizarin yellow R present in water. The adsorption efficiency of CNTs-Ag₂S was evaluated by estimating the Cd(II) adsorption at different concentrations and contact times. The CNTs-Ag₂S could adsorb Cd(II) entirely within 80 min of the contact time, while CNTs and Ag2S could not pursue it. The Cd(II) adsorption followed the pseudo-second-order, and chemisorption was the rate-determining step in the adsorption process. The Weber−Morris intraparticle pore diffusion model revealed that intraparticle diffusion was not the sole rate-controlling step in the Cd(II) adsorption. Instead, it was contributed by the boundary layer effect. In addition, CNTs-Ag₂S could completely degrade alizarin yellow R in water under the illumination of natural sunlight. The Langmuir-Hinshelwood (L-H) model showed that the degradation of alizarin yellow R proceeded with pseudo-first-order kinetics. Overall, CNTs-Ag₂S performed as an efficient adsorbent and a competent photocatalyst. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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13 pages, 4158 KiB

Open AccessArticle

Photocatalytic Degradation of Psychiatric Pharmaceuticals in Hospital WWTP Secondary Effluents Using g-C₃N₄ and g-C₃N₄/MoS₂ Catalysts in Laboratory-Scale Pilot

by Ilaeira Rapti, Vasiliki Boti, Triantafyllos Albanis and Ioannis Konstantinou

Catalysts 2023, 13(2), 252; https://doi.org/10.3390/catal13020252 - 22 Jan 2023

Cited by 8 | Viewed by 1510

Abstract

Today, the pollution caused by a multitude of pharmaceuticals used by humans has been recognized as a major environmental problem. The objective of this study was to evaluate and compare the photocatalytic degradation of ten target psychiatric drugs in hospital wastewater effluents using [...] Read more.

Today, the pollution caused by a multitude of pharmaceuticals used by humans has been recognized as a major environmental problem. The objective of this study was to evaluate and compare the photocatalytic degradation of ten target psychiatric drugs in hospital wastewater effluents using g-C₃N₄ and 1%MoS₂/g-C₃N₄ (1MSCN) as photocatalytic materials. The experiments were performed using real wastewater samples collected from hospital wastewater treatment plant (WWTP) secondary effluent in spiked and inherent pharmaceutical concentration levels. The photocatalytic experiments were performed in a laboratory-scale pilot plant composed of a stainless-steel lamp reactor (46 L) equipped with ten UVA lamps and quartz filters connected in series with a polypropylene recirculation tank (55–100 L). In addition, experiments were carried out in a solar simulator apparatus Atlas Suntest XLS+ at a 500 Wm⁻² irradiation intensity. The analysis of the samples was accomplished by solid-phase extraction, followed by liquid chromatography-Orbitrap high-resolution mass spectrometry. Results showed that the photocatalytic degradation of pharmaceutical compounds followed first-order kinetics. In all cases, 1MSCN presented higher photocatalytic performance than g-C₃N₄. The removal rates of the pharmaceutical compounds were determined above 30% and 54% using g-C₃N₄ and 1MSCN, respectively. Parallel to kinetic studies, the transformation products (TPs) generated during the treatment were investigated. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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19 pages, 3294 KiB

Open AccessArticle

Biochar from Lemon Stalks: A Highly Active and Selective Carbocatalyst for the Oxidation of Sulfamethoxazole with Persulfate

by Spyridon Giannakopoulos, John Vakros, Zacharias Frontistis, Ioannis D. Manariotis, Danae Venieri, Stavros G. Poulopoulos and Dionissios Mantzavinos

Catalysts 2023, 13(2), 233; https://doi.org/10.3390/catal13020233 - 19 Jan 2023

Cited by 6 | Viewed by 1544

Abstract

Pyrolysis of lemon stalks at 850 °C under a limited oxygen atmosphere yields a highly active and selective biochar for the activation of persulfate ion and the oxidation of sulfamethoxazole (SMX). The biochar mainly consists of C and O atoms, with Ca and [...] Read more.

Pyrolysis of lemon stalks at 850 °C under a limited oxygen atmosphere yields a highly active and selective biochar for the activation of persulfate ion and the oxidation of sulfamethoxazole (SMX). The biochar mainly consists of C and O atoms, with Ca and K being the most abundant minerals. It has a moderate specific surface area of 154 m² g⁻¹ and carbonate species, probably in the form of calcium carbonate. Complete degradation of 0.5 mg L⁻¹ SMX can be achieved within 20 min using 500 mg L⁻¹ sodium persulfate (SPS) and 100 mg L⁻¹ biochar in ultrapure water (UPW). The acidic environment positively influences the degradation and adsorption processes, while the complexity of the water matrices usually has a negative impact on the degradation. The presence of chloride accelerates the oxidation of SMX, whose mechanism follows radical and non-radical pathways. Hydroxyl radicals seem to have the dominant contribution, while the electron transfer pathway was proven with electrochemical characterization. The biochar is stable for at least five cycles, and this makes it a good candidate for a sustainable, metal-free catalyst. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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13 pages, 2129 KiB

Open AccessArticle

Photocatalytic Degradation of Pharmaceutical Amisulpride Using g-C₃N₄ Catalyst and UV-A Irradiation

by Maria Antonopoulou, Maria Papadaki, Ilaeira Rapti and Ioannis Konstantinou

Catalysts 2023, 13(2), 226; https://doi.org/10.3390/catal13020226 - 18 Jan 2023

Cited by 10 | Viewed by 1765

Abstract

In the present study, the photocatalytic degradation of amisulpride using g-C₃N₄ catalyst under UV-A irradiation was investigated. The photocatalytic process was evaluated in terms of its effectiveness to remove amisulpride from ultrapure and real municipal wastewater. High removal percentages were [...] Read more.

In the present study, the photocatalytic degradation of amisulpride using g-C₃N₄ catalyst under UV-A irradiation was investigated. The photocatalytic process was evaluated in terms of its effectiveness to remove amisulpride from ultrapure and real municipal wastewater. High removal percentages were achieved in both aqueous matrices. However, a slower degradation rate was observed using wastewater as matrix that could be attributed to its complex chemical composition. The transformation products (TPs) were identified with liquid chromatography–mass spectrometry (LC–MS) in both ultrapure and real municipal wastewater. Based on the identified TPs, the photocatalytic degradation pathways of amisulpride are proposed which include mainly oxidation, dealkylation, and cleavage of the methoxy group. Moreover, the contribution of reactive species to the degradation mechanism was studied using well-documented scavengers, and the significant role of h⁺ and O₂^•− in the reaction mechanism was proved. The evolution of ecotoxicity was also estimated using microalgae Chlorococcum sp. and Dunaliella tertiolecta. Low toxicity was observed during the overall process without the formation of toxic TPs when ultrapure water was used as matrix. In the case of real municipal wastewater, an increased toxicity was observed at the beginning of the process which is attributed to the composition of the matrix. The application of heterogeneous photocatalysis reduced the toxicity, and almost complete detoxification was achieved at the end of the process. Our results are in accordance with literature data that reported that heterogeneous photocatalysis is effective for the removal of amisulpride from aqueous matrices. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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19 pages, 7262 KiB

Open AccessArticle

Photocatalytic Degradation of Organic Dyes Contaminated Aqueous Solution Using Binary CdTiO₂ and Ternary NiCdTiO₂ Nanocomposites

by Shakeel Khan, Awal Noor, Idrees Khan, Mian Muhammad, Muhammad Sadiq and Niaz Muhammad

Catalysts 2023, 13(1), 44; https://doi.org/10.3390/catal13010044 - 26 Dec 2022

Cited by 8 | Viewed by 2765

Abstract

The synergistic effect of binary CdTiO₂ and ternary NiCdTiO₂ on the photocatalytic efficiency of TiO₂ nanoparticles was investigated. The SEM analysis demonstrates spherical TiO₂ NPs of different sizes present in agglomerated form. The structural analysis of the nanocomposites reveals [...] Read more.

The synergistic effect of binary CdTiO₂ and ternary NiCdTiO₂ on the photocatalytic efficiency of TiO₂ nanoparticles was investigated. The SEM analysis demonstrates spherical TiO₂ NPs of different sizes present in agglomerated form. The structural analysis of the nanocomposites reveals a porous structure for TiO₂ with well deposited Cd and Ni NPs. TEM images show NiCdTiO₂ nanocomposites as highly crystalline particles having spherical and cubical geometry with an average particle size of 20 nm. The EDX and XRD analysis confirm the purity and anatase phase of TiO₂, respectively. Physical features of NiCdTiO₂ nanocomposite were determined via BET analysis which shows that the surface area, pore size and pore volume are 61.2 m²/g, 10.6 nm and 0.1 cm³/g, respectively. The absorbance wavelengths of the CdTiO₂ and NiCdTiO₂ nanocomposites have shown red shift as compared to the neat TiO₂ due to coupling with Ni and Cd that results in the enhanced photocatalytic activity. The photocatalytic activity demonstrated that TiO₂, CdTiO₂ and NiCdTiO₂ degrade methylene blue (MB) and methyl green (MG) about 76.59, 82, 86% and 63.5, 88, 97.5%, respectively, at optimum reaction conditions. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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12 pages, 1768 KiB

Open AccessFeature PaperArticle

Insight into the Effect of Anionic–Anionic Co-Doping on BaTiO₃ for Visible Light Photocatalytic Water Splitting: A First-Principles Hybrid Computational Study

by Souraya Goumri-Said and Mohammed Benali Kanoun

Catalysts 2022, 12(12), 1672; https://doi.org/10.3390/catal12121672 - 19 Dec 2022

Cited by 6 | Viewed by 1856

Abstract

In this research, we thoroughly studied the electronic properties and optical absorption characteristics with double-hole coupling of anions–anion combinations for designing effective photocatalysts for water redox using first-principles methods within the hybrid Heyd–Scuseria–Ernzerhof (HSE06) exchange–correlation formalisms. The findings reveal that the values of [...] Read more.

In this research, we thoroughly studied the electronic properties and optical absorption characteristics with double-hole coupling of anions–anion combinations for designing effective photocatalysts for water redox using first-principles methods within the hybrid Heyd–Scuseria–Ernzerhof (HSE06) exchange–correlation formalisms. The findings reveal that the values of formation energy of both the anion mono- and co-doped configurations increase monotonically as the chemical potential of oxygen decreases. The N–N co-doped BaTiO₃ exhibits a more favorable formation energy under an O-poor condition compared with other configurations, indicating that N and N pairs are more likely to be synthesized successfully. Interestingly, all the co-doping configurations give a band gap reduction with suitable position for oxygen production and hydrogen evolution. The obtained results demonstrate that all the co-doped systems constitute a promising candidate for photocatalytic water-splitting reactions. Furthermore, the enhanced ability of the anionic-anionic co-doped BaTiO₃ to absorb visible light and the positions of band edges that closely match the oxidation-reduction potentials of water suggest that these configurations are viable photocatalysts for visible-light water splitting. Therefore, the wide-band gap semiconductor band structures can be tuned by double-hole doping through anionic combinations, and high-efficiency catalysts for water splitting using solar energy can be created as a result. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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13 pages, 1926 KiB

Open AccessFeature PaperArticle

Direct One-Step Seedless Hydrothermal Growth of ZnO Nanostructures on Zinc: Primary Study for Photocatalytic Roof Development for Rainwater Purification

by Marie Le Pivert, Aurélie Piebourg, Stéphane Bastide, Myriam Duc and Yamin Leprince-Wang

Catalysts 2022, 12(10), 1231; https://doi.org/10.3390/catal12101231 - 14 Oct 2022

Cited by 5 | Viewed by 1160

Abstract

To shift towards the greener city, photocatalytic urban infrastructures have emerged as a promising solution for pollution remediation. To reach this goal, the large bandgap semiconductors, such as nontoxic Zinc Oxide (ZnO), already proved their excellent photocatalytic performances. However, integrating and developing cost-effective [...] Read more.

To shift towards the greener city, photocatalytic urban infrastructures have emerged as a promising solution for pollution remediation. To reach this goal, the large bandgap semiconductors, such as nontoxic Zinc Oxide (ZnO), already proved their excellent photocatalytic performances. However, integrating and developing cost-effective and greener photocatalytic surfaces with an easily scaled-up synthesis method and without energy and chemical product overconsumption is still challenging. Therefore, this work proposes to develop a depolluting Zinc (Zn) roof covered by ZnO nanostructures (NSs) using a one-step seedless hydrothermal growth method in 2 h. The feasibility of this synthesis was firstly studied on small areas of Zn (1.25 cm²) before being scaled up to medium-sized areas (25 cm²). The efficiency of this functionalization route for ZnO NSs grown without seed layer was attributed to the presence of Zn²⁺ sites and the native oxide film on the Zn surface. Their photocatalytic efficiency was demonstrated by removing in less than 3 h the Methylene Blue (MB) and Acid Red 14 (AR14) in both DI water and rainwater under UV-light. Promising results were also recorded under solar light. Therefore, the photocatalytic Zn roof functionalized by ZnO NSs is a promising route for rainwater purification by photocatalysis. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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15 pages, 1825 KiB

Open AccessFeature PaperArticle

Auramine O UV Photocatalytic Degradation on TiO₂ Nanoparticles in a Heterogeneous Aqueous Solution

by Cristina Pei Ying Kong, Nurul Amanina A. Suhaimi, Nurulizzatul Ningsheh M. Shahri, Jun-Wei Lim, Muhammad Nur, Jonathan Hobley and Anwar Usman

Catalysts 2022, 12(9), 975; https://doi.org/10.3390/catal12090975 - 30 Aug 2022

Cited by 17 | Viewed by 1920

Abstract

Amongst the environmental issues throughout the world, organic synthetic dyes continue to be one of the most important subjects in wastewater remediation. In this paper, the photocatalytic degradation of the dimethylmethane fluorescent dye, Auramine O (AO), was investigated in a heterogeneous aqueous solution [...] Read more.

Amongst the environmental issues throughout the world, organic synthetic dyes continue to be one of the most important subjects in wastewater remediation. In this paper, the photocatalytic degradation of the dimethylmethane fluorescent dye, Auramine O (AO), was investigated in a heterogeneous aqueous solution with 100 nm anatase TiO₂ nanoparticles (NPs) under 365 nm light irradiation. The effect of irradiation time was systematically studied, and photolysis and adsorption of AO on TiO₂ NPs were also evaluated using the same experimental conditions. The kinetics of AO photocatalytic degradation were pseudo-first order, according to the Langmuir–Hinshelwood model, with a rate constant of 0.048 ± 0.002 min⁻¹. A maximum photocatalytic efficiency, as high as 96.2 ± 0.9%, was achieved from a colloidal mixture of 20 mL (17.78 μmol L⁻³) AO solution in the presence of 5 mg of TiO₂ NPs. The efficiency of AO photocatalysis decreased nonlinearly with the initial concentration and catalyst dosage. Based on the effect of temperature, the activation energy of AO photocatalytic degradation was estimated to be 4.63 kJ mol⁻¹. The effect of pH, additional scavengers, and H₂O₂ on the photocatalytic degradation of AO was assessed. No photocatalytic degradation products of AO were observed using UV–visible and Fourier transform infrared spectroscopy, confirming that the final products are volatile small molecules. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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12 pages, 2826 KiB

Open AccessArticle

The Effect of Arsenic on the Photocatalytic Removal of Methyl Tet Butyl Ether (MTBE) Using Fe₂O₃/MgO Catalyst, Modeling, and Process Optimization

by Akbar Mehdizadeh, Zahra Derakhshan, Fariba Abbasi, Mohammad Reza Samaei, Mohammad Ali Baghapour, Mohammad Hoseini, Eder Claudio Lima and Muhammad Bilal

Catalysts 2022, 12(8), 927; https://doi.org/10.3390/catal12080927 - 22 Aug 2022

Cited by 5 | Viewed by 1507

Abstract

MTBE is an aliphatic matter successfully removed from contaminated water by an advanced oxidation process. Additionally, arsenic is a toxic metalloid that is detected in some water supplies, such as in Iran. Concerning the oxidation potential of arsenic in an aqueous solution, it [...] Read more.

MTBE is an aliphatic matter successfully removed from contaminated water by an advanced oxidation process. Additionally, arsenic is a toxic metalloid that is detected in some water supplies, such as in Iran. Concerning the oxidation potential of arsenic in an aqueous solution, it is expected that its interference in the photocatalytic removal of organic matter includes MTBE. Nevertheless, there is a lack of observation of this effect. In this study, the effect of arsenic on the photocatalytic removal of MTBE using an Fe₂O₃/MgO catalyst under UV radiation was investigated. Using an experimental design, modeling, and optimizing operational parameters, such as the arsenic and MTBE concentrations, catalyst dosage, pH, and reaction time, were studied. The synthesized nanocatalyst had a uniform and spherical morphological structure and contained 33.06% Fe₂O₃ and 45.06% MgO. The results indicate that the best model is related to the quadratic (p-value < 0.0001, R² = 0.97) and that the effect of the MTBE concentration is greater than the others. The highest removal efficiency was taken in an initial concentration of 37.5 mg/L MTBE, 1.58 mg/L Fe₂O₃/MgO, pH 5, and a reaction time of 21.41 min without any As. The removal efficiency was negatively correlated with the initial MTBE concentration and pH, but it was positively associated with the Fe₂O₃/MgO dosage and reaction time. Finally, the presence of arsenic decreased the removal efficiency remarkably (90.90% As = 0.25 μg/L and 61% As = 500 μg/L). Consequently, MTBE was removed by the photocatalytic process caused by Fe₂O₃/MgO, but the presence of arsenic was introduced as a limiting factor. Therefore, pretreatment for the removal of arsenic and more details of this interference effect are suggested. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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16 pages, 4183 KiB

Open AccessArticle

Degradation of Sulfamethoxazole Using a Hybrid CuO_x–BiVO₄/SPS/Solar System

by Konstantinos Kouvelis, Adamantia A. Kampioti, Athanasia Petala and Zacharias Frontistis

Catalysts 2022, 12(8), 882; https://doi.org/10.3390/catal12080882 - 11 Aug 2022

Cited by 15 | Viewed by 1437

Abstract

In recent years, advanced oxidation processes (AOPs) demonstrated great efficiency in eliminating emerging contaminants in aqueous media. However, a majority of scientists believe that one of the main reasons hindering their industrial application is the low efficiencies recorded. This can be partially attributed [...] Read more.

In recent years, advanced oxidation processes (AOPs) demonstrated great efficiency in eliminating emerging contaminants in aqueous media. However, a majority of scientists believe that one of the main reasons hindering their industrial application is the low efficiencies recorded. This can be partially attributed to reactive oxygen species (ROS) scavenging from real water matrix constituents. A promising strategy to cost-effectively increase efficiency is the simultaneous use of different AOPs. Herein, photocatalysis and sodium persulfate activation (SPS) were used simultaneously to decompose the antibiotic sulfamethoxazole (SMX) in ultrapure water (UPW) and real water matrices, such as bottled water (BW) and wastewater (WW). Specifically, copper-promoted BiVO₄ photocatalysts with variable CuO_x (0.75–10% wt.) content were synthesized in powder form and characterized using ΒΕΤ, XRD, DRS, SEM, and HRTEM. Results showed that under simulated solar light irradiation alone, 0.75 Cu.BVO leads to 0.5 mg/L SMX destruction in UPW in a very short treatment time, whereas higher amounts of copper loading decreased SMX degradation. In contrast, the efficiency of all photocatalytic materials dropped significantly in BW and WW. This phenomenon was surpassed using persulfate in the proposed system resulting in synergistic effects, thus significantly improving the efficiency of the combined process. Specifically, when 0.75 Cu.BVO was added in BW, only 40% SMX degradation took place in 120 min under simulated solar irradiation alone, whereas in the solar/SPS/Cu.BVO system, complete elimination was achieved after 60 min. Moreover, ~37%, 45%, and 66% synergy degrees were recorded in WW using 0.75 Cu, 3.0 Cu, and 10.0 Cu.BVO, respectively. Interestingly, experimental results highlight that catalyst screening or process/system examination must be performed in a wide window of operating parameters to avoid erroneous conclusions regarding optimal materials or process combinations for a specific application. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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19 pages, 6448 KiB

Open AccessFeature PaperArticle

Nitrogen and Sulfur Co-Doped Graphene Quantum Dots Anchored TiO₂ Nanocomposites for Enhanced Photocatalytic Activity

by Jishu Rawal, Urooj Kamran, Mira Park, Bishweshwar Pant and Soo-Jin Park

Catalysts 2022, 12(5), 548; https://doi.org/10.3390/catal12050548 - 17 May 2022

Cited by 13 | Viewed by 2859

Abstract

Herein, nitrogen (N) and sulfur (S) co-doped graphene quantum dots (GQDs) using different one-dimensional (1-D) carbon nanomaterials as precursors were synthesized, followed by heterojunction formation with TiO₂. GQDs exhibit unlike physiochemical properties due to the disproportionate ratio of N and S [...] Read more.

Herein, nitrogen (N) and sulfur (S) co-doped graphene quantum dots (GQDs) using different one-dimensional (1-D) carbon nanomaterials as precursors were synthesized, followed by heterojunction formation with TiO₂. GQDs exhibit unlike physiochemical properties due to the disproportionate ratio of N and S heteroatoms and dissimilar reaction parameters. Tailored type-II band gap (E_g) alignment was formed with narrowed E_g value that improves photogenerated electron transfer due to π-conjugation. GQDs-TiO₂ nanocomposites exhibit remarkably high methylene blue (MB) degradation up to 99.78% with 2.3–3 times elevated rate constants as compared with TiO₂. CNF-GQDs-TiO₂ demonstrates the fastest MB degradation (60 min) due to the synergistic effect of nitrogen and sulfur doping, and is considered the most stable photocatalyst among prepared nanocomposites as tested up to three cyclic runs. Whereas, C–O–Ti bonds were not only responsible for nanocomposites strengthening but also provide a charge transfer pathway. Moreover, charge transport behavior, generation of active species, and reaction mechanism were scrutinized via free-radical scavenger analysis. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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Review

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16 pages, 832 KiB

Open AccessReview

Dynamics of Diffusion- and Immobilization-Limited Photocatalytic Degradation of Dyes by Metal Oxide Nanoparticles in Binary or Ternary Solutions

by Nurul Amanina A. Suhaimi, Cristina Pei Ying Kong, Nurulizzatul Ningsheh M. Shahri, Muhammad Nur, Jonathan Hobley and Anwar Usman

Catalysts 2022, 12(10), 1254; https://doi.org/10.3390/catal12101254 - 17 Oct 2022

Cited by 12 | Viewed by 1860

Abstract

Photocatalytic degradation employing metal oxides, such as TiO₂ nanoparticles, as catalysts is an important technique for the removal of synthetic dyes from wastewater under light irradiation. The basic principles of photocatalysis of dyes, the effects of the intrinsic photoactivity of a catalyst, [...] Read more.

Photocatalytic degradation employing metal oxides, such as TiO₂ nanoparticles, as catalysts is an important technique for the removal of synthetic dyes from wastewater under light irradiation. The basic principles of photocatalysis of dyes, the effects of the intrinsic photoactivity of a catalyst, and the conventional non-fundamental factors are well established. Recently reported photocatalysis studies of dyes in single, binary, and ternary solute solutions opened up a new perspective on competitive photocatalytic degradation of the dyes. There has not been a review on the photocatalytic behavior of binary or ternary solutions of dyes. In this regard, this current review article summarizes the photocatalytic behavior of methylene, rhodamine B, and methyl orange in their binary or ternary solutions. This brief overview introduces the importance of the dynamics of immobilization and reactivity of the dyes, the vital roles of molecular conformation and functional groups on their diffusion onto the catalyst surface, and photocatalytic degradation, and provides an understanding of the simultaneous photocatalytic processes of multiple dyes in aqueous systems. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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18 pages, 5181 KiB

Open AccessReview

CuS-Based Nanostructures as Catalysts for Organic Pollutants Photodegradation

by Luminita Isac, Cristina Cazan, Luminita Andronic and Alexandru Enesca

Catalysts 2022, 12(10), 1135; https://doi.org/10.3390/catal12101135 - 28 Sep 2022

Cited by 19 | Viewed by 2744

Abstract

The direct or indirect discharge of toxic and non-biodegradable organic pollutants into water represents a huge threat that affects human health and the environment. Therefore, the treatment of wastewater, using sustainable technologies, is absolutely necessary for reusability. Photocatalysis is considered one of the [...] Read more.

The direct or indirect discharge of toxic and non-biodegradable organic pollutants into water represents a huge threat that affects human health and the environment. Therefore, the treatment of wastewater, using sustainable technologies, is absolutely necessary for reusability. Photocatalysis is considered one of the most innovative advanced techniques used for pollutant removal from wastewater, due to its high efficiency, ease of process, low-cost, and the environmentally friendly secondary compounds that occur. The key of photocatalysis technology is the careful selection of catalysts, usually semiconductor materials with high absorption capacity for solar light, and conductivity for photogenerated charge carriers. Among copper sulfides, CuS (covellite), a semiconductor with different morphologies and bandgap values, is recognized as an important photocatalyst used for the removal of organic pollutants (dyes, pesticides, pharmaceutics etc.) from wastewater. This review deals with recent developments in organic pollutant photodegradation, using as catalysts various CuS nanostructures, consisting of CuS NPs, CuS QDs, and heterojunctions (CuS/ carbon-based materials, CuS/organic semiconductor, CuS/metal oxide). The effects of different synthesis parameters (Cu:S molar ratios, surfactant concentration etc.) and properties (particle size, morphology, bandgap energy, and surface properties) on the photocatalytic performance of CuS-based catalysts for the degradation of various organic pollutants are extensively discussed. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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27 pages, 3368 KiB

Open AccessReview

Surface Modification of Biochar for Dye Removal from Wastewater

by Lalit Goswami, Anamika Kushwaha, Saroj Raj Kafle and Beom-Soo Kim

Catalysts 2022, 12(8), 817; https://doi.org/10.3390/catal12080817 - 26 Jul 2022

Cited by 45 | Viewed by 6184

Abstract

Nowadays, biochar is being studied to a great degree because of its potential for carbon sequestration, soil improvement, climate change mitigation, catalysis, wastewater treatment, energy storage, and waste management. The present review emphasizes on the utilization of biochar and biochar-based nanocomposites to play [...] Read more.

Nowadays, biochar is being studied to a great degree because of its potential for carbon sequestration, soil improvement, climate change mitigation, catalysis, wastewater treatment, energy storage, and waste management. The present review emphasizes on the utilization of biochar and biochar-based nanocomposites to play a key role in decontaminating dyes from wastewater. Numerous trials are underway to synthesize functionalized, surface engineered biochar-based nanocomposites that can sufficiently remove dye-contaminated wastewater. The removal of dyes from wastewater via natural and modified biochar follows numerous mechanisms such as precipitation, surface complexation, ion exchange, cation–π interactions, and electrostatic attraction. Further, biochar production and modification promote good adsorption capacity for dye removal owing to the properties tailored from the production stage and linked with specific adsorption mechanisms such as hydrophobic and electrostatic interactions. Meanwhile, a framework for artificial neural networking and machine learning to model the dye removal efficiency of biochar from wastewater is proposed even though such studies are still in their infancy stage. The present review article recommends that smart technologies for modelling and forecasting the potential of such modification of biochar should be included for their proper applications. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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