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Innovative Nanomaterials and Nanocomposites for Photocatalytic Removal of Organic Pollutants

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A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Energy and Catalysis".

Deadline for manuscript submissions: closed (30 November 2020) | Viewed by 38916

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Special Issue Editor

Dr. Olga Sacco

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Department of Chemistry and Biology "A.Zambelli", University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, SA, Italy
Interests: synthesis and characterization of catalytic materials; phosphors-based nanomaterials; nanostructured photocatalysts and supports; photocatalysis for the removal of pollutants from water and wastewater; membrane separation processes
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Special Issue Information

Dear Colleagues,

Heterogeneous photocatalysis can be considered as one of the main challenges in the field of water and wastewater treatment, because a heterogeneous photocatalytic process is able to work at ambient temperature and atmospheric pressure.

Currently, ZnO- or TiO₂-based nanomaterials are the most-studied photocatalysts and have attracted a great deal of interest due to their unique physical-chemical properties. Consequently, they have been exploited as promising materials for the removal of a wide variety of organic pollutants present in water and wastewater, as well as gaseous streams. On the other hand, despite the great benefits associated to TiO₂- or ZnO-based nanomaterials, there are still open questions about the synthesis and photocatalytic efficiency of novel nanomaterials and nanocomposites as well as the design of nanostructured semiconducting materials immobilized on macroscopic supports.

This Special Issue is focused on “Innovative Nanomaterials and Nanocomposites for Photocatalytic Removal of Organic Pollutants”, featuring the state-of-the-art in this field. Research papers related to the synthesis and characterization of novel nanomaterials or nanocomposites (active under UV or visible light, as well as under solar light) and their uses in the removal of pollutants form liquid and gaseous phases are welcome in this Special Issue.

Dr. Olga Sacco
Guest Editor

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Keywords

photocatalysis
nanomaterials
nanocomposites
nanostructured photocatalysts
macroscopic supports
UV and visible light
solar light
water and wastewater treatment
gaseous streams treatment

Published Papers (11 papers)

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Research

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17 pages, 4083 KiB

Open AccessArticle

Incorporation of NiO into SiO₂, TiO₂, Al₂O₃, and Na_4.2Ca_2.8(Si₆O₁₈) Matrices: Medium Effect on the Optical Properties and Catalytic Degradation of Methylene Blue

by Carlos Diaz, María L. Valenzuela, Olga Cifuentes-Vaca, Marjorie Segovia and Miguel A. Laguna-Bercero

Nanomaterials 2020, 10(12), 2470; https://doi.org/10.3390/nano10122470 - 10 Dec 2020

Cited by 7 | Viewed by 2362

Abstract

The medium effect of the optical and catalytic degradation of methylene blue was studied in the NiO/SiO₂, NiO/TiO₂, NiO/Al₂O₃, and NiO/Na_4.2Ca_2.8(Si₆O₁₈) composites, which were prepared by a solid-state method. The new composites were characterized by XRD (X-ray diffraction of powder), SEM/EDS, TEM, and HR-TEM. The size of the NiO nanoparticles obtained from the PSP-4-PVP (polyvinylpyrrolidone) precursors inside the different matrices follow the order of SiO₂ > TiO₂ > Al₂O₃. However, NiO nanoparticles obtained from the chitosan precursor does not present an effect on the particle size. It was found that the medium effect of the matrices (SiO₂, TiO₂, Al₂O₃, and Na_4.2Ca_2.8(Si₆O₁₈)) on the photocatalytic methylene blue degradation, can be described as a specific interaction of the NiO material acting as a semiconductor with the M_xO_y materials through a possible p-n junction. The highest catalytic activity was found for the TiO₂ and glass composites where a favorable p-n junction was formed. The isolating character of Al₂O₃ and SiO₂ and their non-semiconductor behavior preclude this interaction to form a p-n junction, and thus a lower catalytic activity. NiO/SiO₂ and NiO/Na_4.2Ca_2.8(Si₆O₁₈) showed a similar photocatalytic behavior. On the other hand, the effect of the matrix on the optical properties for the NiO/SiO₂, NiO/TiO₂, NiO/Al₂O₃, and NiO/Na_4.2Ca_2.8(Si₆O₁₈) composites can be described by the different dielectric constants of the SiO₂, TiO₂, Al₂O₃, Na_4.2Ca_2.8(Si₆O₁₈) matrices. The maxima absorption of the composites (λ_max) exhibit a direct relationship with the dielectric constants, while their semiconductor bandgap (E_g) present an inverse relationship with the dielectric constants. A direct relationship between λ_max and E_g was found from these correlations. The effect of the polymer precursor on the particle size can explain some deviations from this relationship, as the correlation between the particle size and absorption is well known. Finally, the NiO/Na_4.2Ca_2.8(Si₆O₁₈) composite was reported in this work for the first time. Full article

(This article belongs to the Special Issue Innovative Nanomaterials and Nanocomposites for Photocatalytic Removal of Organic Pollutants)

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12 pages, 4267 KiB

Open AccessArticle

Facile Preparation of Wormlike Graphitic Carbon Nitride for Photocatalytic Degradation of Ustiloxin A

by Yanfei Wu, Jin Mao, Chuanwei Ao, Di Sun, Xiaorui Wang, Qin Hu, Xuezhu Du and Feng Sheng

Nanomaterials 2020, 10(11), 2256; https://doi.org/10.3390/nano10112256 - 14 Nov 2020

Cited by 2 | Viewed by 1825

Abstract

Natural toxic contaminants have been recognized as threats to human health. Ustiloxins are the toxic secondary metabolites of fungus generated from rice false smut disease, which are harmful to animal/human reproduction and growth. However, there are rare researches on the control and reduction of ustiloxins through physical, chemical and biological ways. Herein, we demonstrated that photocatalysis of semiconductor nanomaterials could be as a potential way to degrade or mitigate the contamination of ustiloxin A. A kind of wormlike graphitic carbon nitride (g-C₃N₄) was facilely prepared from modified dicyandiamide precursor via pyrolysis method and characterized by X-ray diffraction, high-resolution transmission electron microscope and X-ray photoelectron spectroscopy etc. It was found that g-C₃N₄ from modified dicyandiamide precursor showed better activity for ustiloxin A degradation under visible light irradiation than that of pristine g-C₃N₄. This was ascribed to the lager specific surface area, more uniform microstructure, better photogenerated charges separation and transformation of wormlike g-C₃N₄ compared with pristine g-C₃N₄. Most important, the structure of degradation intermediates and the possible pathway were proposed based on the results of high-performance liquid chromatography-mass spectrometry after 80 min photoreaction treatment. Our findings may provide a green, efficient way for ustiloxins mitigation and useful information for future study. Full article

(This article belongs to the Special Issue Innovative Nanomaterials and Nanocomposites for Photocatalytic Removal of Organic Pollutants)

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15 pages, 5957 KiB

Open AccessArticle

One-Pot Hydrothermal Synthesis of La-Doped ZnIn₂S₄ Microspheres with Improved Visible-Light Photocatalytic Performance

by Tiekun Jia, Ming Liu, Chunyang Zheng, Fei Long, Zhiyu Min, Fang Fu, Dongsheng Yu, Jili Li, Joong Hee Lee and Nam Hoon Kim

Nanomaterials 2020, 10(10), 2026; https://doi.org/10.3390/nano10102026 - 14 Oct 2020

Cited by 29 | Viewed by 3563

Abstract

Impurity element doping is extensively taken as one of the most efficient strategies to regulate the electronic structure as well as the rate of photogenerated charge separation of photocatalysts. Herein, a one-pot hydrothermal synthesis process was exploited to obtain La-doped ZnIn₂S₄ microspheres, aiming at gaining insight into the role that doping ions played in the improvement of pollutant photodegradation. Systematical characterization means, comprising of X–ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–vis) diffuse reflection spectroscopy and Raman spectra, combination with high-resolution transmission electron microscopy (HRTEM), were employed to in depth reveal the concomitancy of La ions and ZnIn₂S₄ crystal lattice. The results showed that the La-doped ZnIn₂S₄ samples exhibited a slightly wider and stronger spectral absorption than pristine ZnIn₂S₄; and the specific surface area of doped ZnIn₂S₄ samples was a bit larger. The La-doped ZnIn₂S₄ electrodes showed improved photocurrent response, and the photocurrent density reached a maximum value at La content of 1.5 wt%. As expected, La-doped ZnIn₂S₄ samples exhibited a remarkable enhancement of photocatalytic behaviour toward the photodegradation of tetracycline hydrochloride (TCH) and methyl orange (MO). The prominently enhanced photoactivity of doped ZnIn₂S₄ samples was due to the synergistic effect of the elevated visible-light absorption ability and effective photogenerated charge carriers’ separation. Full article

(This article belongs to the Special Issue Innovative Nanomaterials and Nanocomposites for Photocatalytic Removal of Organic Pollutants)

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9 pages, 1512 KiB

Open AccessArticle

Separation of Radionuclides from Spent Decontamination Fluids via Adsorption onto Titanium Dioxide Nanotubes after Photocatalytic Degradation

by Monika Lyczko, Barbara Wiaderek and Aleksander Bilewicz

Nanomaterials 2020, 10(8), 1553; https://doi.org/10.3390/nano10081553 - 7 Aug 2020

Cited by 6 | Viewed by 2260

Abstract

A one-step process combining the photocatalytic degradation of radionuclide complexes and the adsorption of liberated radionuclides on titanium dioxide nanotubes was developed and tested for the purification of aqueous waste produced from chemical decontamination of nuclear power plant circuit components. Among the tested forms of TiO₂, only nanotubes exhibit both high photocatalytic activity and sorption ability, which support their application in a one-step purification process. The obtained results indicate that the photocatalytic degradation of complexes followed by the sorption of the radionuclides onto TiO₂ nanotubes offers a promising route for treating spent decontamination fluids. Full article

(This article belongs to the Special Issue Innovative Nanomaterials and Nanocomposites for Photocatalytic Removal of Organic Pollutants)

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17 pages, 5537 KiB

Open AccessArticle

Synthesis, Characterization and Application of Iron(II) Doped Copper Ferrites (Cu^II_(x)Fe^II_(1-x)Fe^III₂O₄) as Novel Heterogeneous Photo-Fenton Catalysts

by Asfandyar Khan, Zsolt Valicsek and Ottó Horváth

Nanomaterials 2020, 10(5), 921; https://doi.org/10.3390/nano10050921 - 9 May 2020

Cited by 14 | Viewed by 3079

Abstract

The heterogeneous photo-Fenton type system has huge fame in the field of wastewater treatment due to its reusability and appreciable photoactivity within a wide pH range. This research investigates the synthesis and characterization of iron(II) doped copper ferrite (Cu^II_(x)Fe^II_(1-x)Fe^III₂O₄ nanoparticles (NPs) and their photocatalytic applications for the degradation of methylene blue (MB) as a model dye. The NPs were prepared via simple co-precipitation technique and calcination. The NPs were characterized by using Raman spectroscopy, X-ray diffractometry (XRD), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS). SEM reveals the structural change from the spherical-like particles into needle-like fine particles as the consequence of the increasing ratio of copper(II) in the ferrites, accompanied by the decrease of the optical band-gap energies from 2.02 to 1.25 eV. The three major determinants of heterogeneous photo-Fenton system, namely NPs concentration, hydrogen peroxide concentration and pH, on the photocatalytic degradation of MB were studied. The reusability of NPs was found to be continuously increasing during 4 cycles. It was concluded that iron(II) doped copper ferrites, due to their favorable band-gap energies and peculiar structures, exhibit a strong potential for photocatalytic-degradation of dyes, for example, MB. Full article

(This article belongs to the Special Issue Innovative Nanomaterials and Nanocomposites for Photocatalytic Removal of Organic Pollutants)

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13 pages, 2833 KiB

Open AccessArticle

Pb-Free Cs₃Bi₂I₉ Perovskite as a Visible-Light-Active Photocatalyst for Organic Pollutant Degradation

by Bianca-Maria Bresolin, Carsten Günnemann, Detlef W. Bahnemann and Mika Sillanpää

Nanomaterials 2020, 10(4), 763; https://doi.org/10.3390/nano10040763 - 16 Apr 2020

Cited by 48 | Viewed by 5720

Abstract

In our work, we employed Cs₃Bi₂I₉ as a visible-light-active photocatalyst, synthesized with a low-temperature solvothermal method. The morphological and structural properties of the as-prepared perovskite were investigated, and the results were compared to previous studies to confirm its nature and the quality of the synthesis procedure. Transient absorption spectroscopy was applied in order to investigate the generation and lifetime of photogenerated charge carriers, revealing their formation after visible light excitation. The potential photocatalytic activity of the as-prepared metal halide perovskite was applied for the removal of Rhodamine B in aqueous solution, demonstrating an excellent activity of 93% after 180 min under visible-light irradiation. The current research aims to provide insights into the design of a new visible-light-active photocatalyst, Cs₃Bi₂I₉, selected for its high application value in the field of advanced materials for light harvesting. Full article

(This article belongs to the Special Issue Innovative Nanomaterials and Nanocomposites for Photocatalytic Removal of Organic Pollutants)

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13 pages, 4394 KiB

Open AccessArticle

Liquid-Plasma Hydrogenated Synthesis of Gray Titania with Engineered Surface Defects and Superior Photocatalytic Activity

by Feng Zhang, Guang Feng, Mengyun Hu, Yanwei Huang and Heping Zeng

Nanomaterials 2020, 10(2), 342; https://doi.org/10.3390/nano10020342 - 17 Feb 2020

Cited by 13 | Viewed by 2360

Abstract

Defect engineering in photocatalysts recently exhibits promising performances in solar-energy-driven reactions. However, defect engineering techniques developed so far rely on complicated synthesis processes and harsh experimental conditions, which seriously hinder its practical applications. In this work, we demonstrated a facile mass-production approach to synthesize gray titania with engineered surface defects. This technique just requires a simple liquid-plasma treatment under low temperature and atmospheric pressure. The in situ generation of hydrogen atoms caused by liquid plasma is responsible for hydrogenation of TiO₂. Electron paramagnetic resonance (EPR) measurements confirm the existence of surface oxygen vacancies and Ti³⁺ species in gray TiO_2−x. Both kinds of defects concentrations are well controllable and increase with the output plasma power. UV–Vis diffused reflectance spectra show that the bandgap of gray TiO_2−x is 2.9 eV. Due to its extended visible-light absorption and engineered surface defects, gray TiO_2−x exhibits superior visible-light photoactivity. Rhodamine B was used to evaluate the visible-light photodegradation performance, which shows that the removal rate constant of gray TiO_2−x reaches 0.126 min⁻¹ and is 6.5 times of P25 TiO₂. The surface defects produced by liquid-plasma hydrogenation are proved stable in air and water and could be a candidate hydrogenation strategy for other photocatalysts. Full article

(This article belongs to the Special Issue Innovative Nanomaterials and Nanocomposites for Photocatalytic Removal of Organic Pollutants)

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11 pages, 3258 KiB

Open AccessArticle

Enhanced Degradation of Sulfamethoxazole (SMX) in Toilet Wastewater by Photo-Fenton Reactive Membrane Filtration

by Shaobin Sun, Hong Yao, Xinyang Li, Shihai Deng, Shenlong Zhao and Wen Zhang

Nanomaterials 2020, 10(1), 180; https://doi.org/10.3390/nano10010180 - 20 Jan 2020

Cited by 18 | Viewed by 3925

Abstract

Pharmaceutical residuals are increasingly detected in natural waters, which made great threat to the health of the public. This study evaluated the utility of the photo-Fenton ceramic membrane filtration toward the removal and degradation of sulfamethoxazole (SMX) as a model recalcitrant micropollutant. The photo-Fenton catalyst Goethite (α-FeOOH) was coated on planar ceramic membranes as we reported previously. The removal of SMX in both simulated and real toilet wastewater were assessed by filtering the feed solutions with/without H₂O₂ and UV irradiation. The SMX degradation rate reached 87% and 92% respectively in the presence of UV/H₂O₂ for the original toilet wastewater (0.8 ± 0.05 ppb) and toilet wastewater with a spiked SMX concentration of 100 ppb. The mineralization and degradation by-products were both assessed under different degradation conditions to achieve deeper insight into the degradation mechanisms during this photo-Fenton reactive membrane filtration. Results showed that a negligible removal rate (e.g., 3%) of SMX was obtained when only filtering the feed solution through uncoated or catalyst-coated membranes. However, the removal rates of SMX were significantly increased to 67% (no H₂O₂) and 90% (with H₂O₂) under UV irradiation, respectively, confirming that photo-Fenton reactions played the key role in the degradation/mineralization process. The highest apparent quantum yield (AQY) reached up to approximately 27% when the H₂O₂ was 10 mmol·L⁻¹ and UV254 intensity was 100 μW·cm⁻². This study lays the groundwork for reactive membrane filtration to tackle the issues from micropollution. Full article

(This article belongs to the Special Issue Innovative Nanomaterials and Nanocomposites for Photocatalytic Removal of Organic Pollutants)

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15 pages, 3573 KiB

Open AccessArticle

Highly Robust and Selective System for Water Pollutants Removal: How to Transform a Traditional Photocatalyst into a Highly Robust and Selective System for Water Pollutants Removal

by Olga Sacco, Vincenzo Vaiano, Christophe Daniel, Wanda Navarra and Vincenzo Venditto

Nanomaterials 2019, 9(11), 1509; https://doi.org/10.3390/nano9111509 - 23 Oct 2019

Cited by 23 | Viewed by 2314

Abstract

Highly porous monolithic aerogels based on ZnO photocatalyst and syndiotactic polystyrene (s-PS) were obtained by supercritical CO₂ treatment of ZnO/s-PS gels. The prepared aerogels were characterized and their photocatalytic activity was evaluated using phenol and toluene as water pollutant models. The s-PS nanoporous crystalline phase, able to absorb pollutant molecules, was proven to be necessary to ensure high photocatalytic efficiency as the aerogel acts not only as a support, but also as pollutant pre-concentrator. The reusability of ZnO/s-PS aerogels is also strong showing no decrease in photocatalytic activity after six consecutive degradation trials. Finally, the aerogel matrix prevents ZnO dissolution occurring under acidic conditions and promotes a selective removal of the pollutants. The synergy between the photocatalyst and the innovative polymeric support provides the composite system with robustness, chemical stability, easy recovery after treatment, high efficiency of pollutant removal with a marked selectivity which make these materials promising for large scale applications. Full article

(This article belongs to the Special Issue Innovative Nanomaterials and Nanocomposites for Photocatalytic Removal of Organic Pollutants)

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14 pages, 2789 KiB

Open AccessArticle

Enhanced Photocatalytic Degradation of Organic Dyes via Defect-Rich TiO₂ Prepared by Dielectric Barrier Discharge Plasma

by Yanqin Li, Wei Wang, Fu Wang, Lanbo Di, Shengchao Yang, Shengjie Zhu, Yongbin Yao, Cunhua Ma, Bin Dai and Feng Yu

Nanomaterials 2019, 9(5), 720; https://doi.org/10.3390/nano9050720 - 9 May 2019

Cited by 57 | Viewed by 4577

Abstract

The dye wastewater produced in the printing and dyeing industry causes serious harm to the natural environment. TiO₂ usually shows photocatalytic degradation of dye under the irradiation ultravilet light rather than visible light. In this work, a large number of oxygen vacancies and Ti³⁺ defects were generated on the surface of the TiO₂ nanoparticles via Ar plasma. Compared with pristine TiO₂ nanoparticles, the as-obtained Ar plasma-treated TiO₂ (Ar-TiO₂) nanoparticles make the energy band gap reduce from 3.21 eV to 3.17 eV and exhibit enhanced photocatalytic degradation of organic dyes. The Ar-TiO₂ obtained exhibited excellent degradation properties of methyl orange (MO); the degradation rate under sunlight irradiation was 99.6% in 30 min, and the photocatalytic performance was about twice that of the original TiO₂ nanoparticles (49%). The degradation rate under visible light (λ > 400 nm) irradiation was 89% in 150 min, and the photocatalytic performance of the Ar-TiO₂ was approaching ~4 times higher than that of the original TiO₂ nanoparticles (23%). Ar-TiO₂ also showed good degradation performance in degrading rhodamine B (Rho B) and methylene blue (MB). We believe that this plasma strategy provides a new method for improving the photocatalytic activity of other metal oxides. Full article

(This article belongs to the Special Issue Innovative Nanomaterials and Nanocomposites for Photocatalytic Removal of Organic Pollutants)

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Review

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47 pages, 6481 KiB

Open AccessFeature PaperReview

Recent Progress in the Abatement of Hazardous Pollutants Using Photocatalytic TiO₂-Based Building Materials

by Anantha-Iyengar Gopalan, Jun-Cheol Lee, Gopalan Saianand, Kwang-Pill Lee, Prashant Sonar, Rajarathnam Dharmarajan, Yao-long Hou, Ki-Yong Ann, Venkatramanan Kannan and Wha-Jung Kim

Nanomaterials 2020, 10(9), 1854; https://doi.org/10.3390/nano10091854 - 16 Sep 2020

Cited by 48 | Viewed by 6230

Abstract

Titanium dioxide (TiO₂) has been extensively investigated in interdisciplinary research (such as catalysis, energy, environment, health, etc.) owing to its attractive physico-chemical properties, abundant nature, chemical/environmental stability, low-cost manufacturing, low toxicity, etc. Over time, TiO₂-incorporated building/construction materials have been utilized for mitigating potential problems related to the environment and human health issues. However, there are challenges with regards to photocatalytic efficiency improvements, lab to industrial scaling up, and commercial product production. Several innovative approaches/strategies have been evolved towards TiO₂ modification with the focus of improving its photocatalytic efficiency. Taking these aspects into consideration, research has focused on the utilization of many of these advanced TiO₂ materials towards the development of construction materials such as concrete, mortar, pavements, paints, etc. This topical review focuses explicitly on capturing and highlighting research advancements in the last five years (mainly) (2014–2019) on the utilization of various modified TiO₂ materials for the development of practical photocatalytic building materials (PBM). We briefly summarize the prospective applications of TiO₂-based building materials (cement, mortar, concretes, paints, coating, etc.) with relevance to the removal of outdoor/indoor NO_x and volatile organic compounds, self-cleaning of the surfaces, etc. As a concluding remark, we outline the challenges and make recommendations for the future outlook of further investigations and developments in this prosperous area. Full article

(This article belongs to the Special Issue Innovative Nanomaterials and Nanocomposites for Photocatalytic Removal of Organic Pollutants)

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