Special Issue "New Trends in the Photocatalytic Removal of Organic Dyes"

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Photocatalysis".

Deadline for manuscript submissions: 30 April 2019

Special Issue Editor

Guest Editor
Prof. Vincenzo Vaiano

University Salerno, Department of Industrial Engineering, Via Giovanni Paolo 2 132, I-84084 Fisciano, Salerno, Italy
Website | E-Mail
Interests: photocatalysis for sustainable chemistry, photocatalytic and photo-Fenton processes for pollutant removal in wastewater, catalytic combustion of sewage sludge, decomposition and oxidative decomposition of H2S, hydrolysis of COS in the liquid phase

Special Issue Information

Dear Colleagues,

Currently, different types of dyes consisting of varied chemical compounds are used in the production of consumer products, including paints, textiles, printing inks, paper, and plastics, depending on the type of textile or product being dyed. The effluent generated by these activities are one of the main causes of environmental pollution, because the effluent coming from the dyeing industry is highly colored, causing damage to aquatic life. For this reason, water pollution due to the dyeing industry is a matter of great concern, as large quantities of effluent are discharged into water bodies. However, due to the low biodegradability of dyes, the typical biological treatment processes are not very effective in the treatment of wastewater containing dyes. In this context, heterogeneous photocatalysis can be effectively exploited for the removal of various dye pollutants present in liquid media. Heterogeneous photocatalysis may represent one of the main challenges in the field of the treatment and decontamination of water, because it is able to work at ambient temperature and atmospheric pressure. Its operating principle is based on the simultaneous action of the light source and a catalyst (semi-conductor), which allows the degradation of organic pollutants.

This Special Issue is focused on “New trends in the Photocatalytic Removal of Organic Dyes”, featuring the state-of-the-art in this field. Research papers related to the synthesis and characterization of novel photocatalysts (active under UV or visible light, as well as under solar light) and their uses in the removal of organic dyes from aqueous solutions are welcome in this Special Issue.

Prof. Vincenzo Vaiano
Guest Editor

Manuscript Submission Information

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Keywords

  • Heterogeneous photocatalysis
  • Organic dyes in water
  • Novel photocatalysts
  • Doped semiconductors
  • Hybrid systems
  • UV light, visible light, solar light

Published Papers (6 papers)

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Research

Open AccessArticle Zinc Oxide Nanoparticles Obtained by Supercritical Antisolvent Precipitation for the Photocatalytic Degradation of Crystal Violet Dye
Catalysts 2019, 9(4), 346; https://doi.org/10.3390/catal9040346
Received: 20 March 2019 / Revised: 3 April 2019 / Accepted: 5 April 2019 / Published: 9 April 2019
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Abstract
In this work, the synthesis of zinc oxide (ZnO) photocatalyst from thermal decomposition of zinc acetate (ZnAc) nanoparticles obtained by supercritical antisolvent (SAS) precipitation was investigated. The optimization of calcination conditions of the SAS ZnAc was carried out, studying the effect of temperature [...] Read more.
In this work, the synthesis of zinc oxide (ZnO) photocatalyst from thermal decomposition of zinc acetate (ZnAc) nanoparticles obtained by supercritical antisolvent (SAS) precipitation was investigated. The optimization of calcination conditions of the SAS ZnAc was carried out, studying the effect of temperature (in the range 300–600 °C) on the production of ZnO nanoparticles. In particular, it was demonstrated that the organic residues in ZnO and its particle size, thus the specific surface area, strongly affect the photocatalytic performances. SAS micronization of ZnAc produces regular nanoparticles with a mean diameter of about 54.5 ± 11.5 nm, whereas unprocessed ZnAc is characterized by very large crystals. The experimental results evidenced that ZnAc prepared by SAS process calcined at 500 °C showed a regular nanometric structure (mean diameter: 65.0 ± 14.5 nm) and was revealed to be the best choice for the photocatalytic removal of crystal violet dye (CV). In fact, the photocatalytic activity performances of ZnO nanoparticles prepared by this route were higher with respect to that of ZnO from unprocessed ZnAc calcined at 500 °C (which is characterized by irregular tetrapods with mean size 181.1 ± 65.5 nm). The optimized photocatalyst was able to assure the complete CV decolorization in 60 min of UV irradiation time and a mineralization degree higher than 90% after 120 min of treatment time. Full article
(This article belongs to the Special Issue New Trends in the Photocatalytic Removal of Organic Dyes)
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Open AccessArticle Dye-sensitized Photocatalyst of Sepiolite for Organic Dye Degradation
Catalysts 2019, 9(3), 235; https://doi.org/10.3390/catal9030235
Received: 10 January 2019 / Revised: 25 February 2019 / Accepted: 26 February 2019 / Published: 4 March 2019
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Abstract
The photocatalytic activity of sepiolite was examined for degradation of several dye compounds under visible light irradiation. Higher adsorption capacities and greater photocatalytic performance of cationic dyes (rhodamine B and methylene blue) were observed on sepiolite, in comparison with anionic dyes (orange II [...] Read more.
The photocatalytic activity of sepiolite was examined for degradation of several dye compounds under visible light irradiation. Higher adsorption capacities and greater photocatalytic performance of cationic dyes (rhodamine B and methylene blue) were observed on sepiolite, in comparison with anionic dyes (orange II and trypan blue). Superiority in the photocatalytic activity of cationic dyes is attributed to the strong electrostatic attraction and photosensitization properties of cationic dye molecules. Sepiolite has degraded 45.3% rhodamine B within 120 min, which is the greatest photocatalytic degradation efficiency when compared with other dyes. Subsequently, the reusability of spent sepiolite after adsorption of rhodamine B was evaluated by the degradation of trypan blue under the visible light irradiation. The photocatalytic degradation performance of trypan blue by spent sepiolite after adsorption of rhodamine B increased about twice as much as with pristine sepiolite, indicating that the dye-sensitized photocatalytic process could enhance the photocatalytic degradation ability of sepiolite. Through radical scavenger tests, it was found that a superoxide radical is mainly responsible for rhodamine B degradation. The possible mechanism of rhodamine B degradation under visible light irradiation was proposed. The sepiolite could be a potential catalyst for the degradation of organic pollutants in wastewater under solar light. Full article
(This article belongs to the Special Issue New Trends in the Photocatalytic Removal of Organic Dyes)
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Open AccessArticle Fluorinated and Platinized Titania as Effective Materials in the Photocatalytic Treatment of Dyestuffs and Stained Wastewater Coming from Handicrafts Factories
Catalysts 2019, 9(2), 179; https://doi.org/10.3390/catal9020179
Received: 17 January 2019 / Revised: 7 February 2019 / Accepted: 10 February 2019 / Published: 14 February 2019
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Abstract
In this study, commercial and lab-prepared TiO2 were modified by fluorination and platinum photodeposition; and the effect of these modifications over the physicochemical and photocatalytic properties of TiO2 was evaluated. It was found that F and Pt addition leads to the [...] Read more.
In this study, commercial and lab-prepared TiO2 were modified by fluorination and platinum photodeposition; and the effect of these modifications over the physicochemical and photocatalytic properties of TiO2 was evaluated. It was found that F and Pt addition leads to the modification of the optical and textural properties of TiO2. The materials prepared were tested in the photocatalytic degradation of different organic dyestuffs such as methylene blue (MB) and methyl orange (MO); the degradation of commercial anilines employed in the staining of natural fibers was also evaluated. Photocatalysis was also studied in this work as an eco-friendly treatment of wastewater coming from handicrafts factories. In general it was observed that the effectiveness of the photocatalytic treatment strongly depends on the substrate to be degraded, thus, fluorinated and platinized commercial Titania (Pt-F-P25) showed the best photocatalytic performance in the MB and MO photodegradation and in contrast, in the case of the anilines the highest degradation was obtained over commercial TiO2 fluorinated (F-P25). These results can be explained by differences observed in the structure and in the adsorption of these dyestuffs over the photocatalysts surfaces. F-P25 photocatalyst also demonstrated to be the best material for the treatment of real wastewater coming from handicrafts factories. Full article
(This article belongs to the Special Issue New Trends in the Photocatalytic Removal of Organic Dyes)
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Open AccessArticle De-Ethylation and Cleavage of Rhodamine B by a Zirconium Phosphate/Silver Bromide Composite Photocatalyst
Catalysts 2019, 9(1), 3; https://doi.org/10.3390/catal9010003
Received: 15 November 2018 / Revised: 10 December 2018 / Accepted: 17 December 2018 / Published: 21 December 2018
Cited by 1 | PDF Full-text (4220 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A composite heterogeneous photocatalyst based on silver bromide was prepared by a reaction of silver exchanged zirconium phosphate (ZrP) and HBr. The ZrP/AgBr composite containing 53 wt% AgBr was tested in the photocatalytic degradation of Rhodamine B (RhB) and exhibited higher catalytic activity [...] Read more.
A composite heterogeneous photocatalyst based on silver bromide was prepared by a reaction of silver exchanged zirconium phosphate (ZrP) and HBr. The ZrP/AgBr composite containing 53 wt% AgBr was tested in the photocatalytic degradation of Rhodamine B (RhB) and exhibited higher catalytic activity with respect to pure AgBr. As a matter of fact, the time needed to achieve a percentage of chromophore cleavage of about 90% was 3 min for the composite versus the 30 min needed for pure AgBr. The ZrP/AgBr composite turned out to be stable for at least three consecutive cycles. The UV-Vis spectra of the RhB solution, recorded at different irradiation times, were also decomposed and the concentration of the species formed by de-ethylation and cleavage processes during photocatalysis were calculated; the data obtained for the AgBr-based catalysis were also compared with those for the AgCl-based catalysis, and the degradation mechanism was suggested for both catalytic systems. Full article
(This article belongs to the Special Issue New Trends in the Photocatalytic Removal of Organic Dyes)
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Open AccessArticle Photocatalytic Degradation of Methylene Blue over TiO2 Pretreated with Varying Concentrations of NaOH
Catalysts 2018, 8(12), 575; https://doi.org/10.3390/catal8120575
Received: 29 September 2018 / Revised: 8 November 2018 / Accepted: 15 November 2018 / Published: 22 November 2018
Cited by 3 | PDF Full-text (4008 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, different NaOH concentrations (2, 5, 10, and 15 M) were used to treat {001}TiO2. The effect of NaOH on the crystal structure, morphology, optical properties, light raw electronic-hole recombination, and degradation performance of {001}TiO2 on methylene blue [...] Read more.
In this paper, different NaOH concentrations (2, 5, 10, and 15 M) were used to treat {001}TiO2. The effect of NaOH on the crystal structure, morphology, optical properties, light raw electronic-hole recombination, and degradation performance of {001}TiO2 on methylene blue were studied. The results demonstrate that rutile TiO2 appeared when the NaOH concentration was as high as 10 M, showing much better photolytic performance than others. As the concentration of sodium hydroxide increases, the morphology changes accordingly. The specific surface area increases and the optical electronic-hole recombination rate decreases. Radical scavenging tests showed that hydroxyl radical and hole are very important in photocatalysis. Full article
(This article belongs to the Special Issue New Trends in the Photocatalytic Removal of Organic Dyes)
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Open AccessFeature PaperArticle Photoelectrocatalytic vs. Photocatalytic Degradation of Organic Water Born Pollutants
Catalysts 2018, 8(10), 455; https://doi.org/10.3390/catal8100455
Received: 7 September 2018 / Revised: 10 October 2018 / Accepted: 10 October 2018 / Published: 15 October 2018
Cited by 1 | PDF Full-text (1806 KB) | HTML Full-text | XML Full-text
Abstract
The azo dye Basic Blue 41 was subjected to photocatalytic and photoelectrocatalytic degradation using nanopararticulate titania films deposited on either glass slides or Fluorine doped Tin Oxide (FTO) transparent electrodes. The degradation was carried out by irradiating titania films with weak ultraviolet (UVA) [...] Read more.
The azo dye Basic Blue 41 was subjected to photocatalytic and photoelectrocatalytic degradation using nanopararticulate titania films deposited on either glass slides or Fluorine doped Tin Oxide (FTO) transparent electrodes. The degradation was carried out by irradiating titania films with weak ultraviolet (UVA) radiation. The degradation was faster when using FTO as a titania support even without bias and was further accelerated under forward electric bias. This result was explained by enhanced electron-hole separation even in the case of the unbiased titania/FTO combination. This system for organic material photocatalytic degradation was also successfully applied to the degradation of the anti-inflammatory drug piroxicam, which demonstrated a well distinguished degradation behavior in going from a plain glass support to unbiased and biased FTO. The degradation pathway of piroxicam has been additionally studied using liquid chromatography-accurate mass spectrometry analysis. Full article
(This article belongs to the Special Issue New Trends in the Photocatalytic Removal of Organic Dyes)
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Graphical abstract

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Photoelectrocatalytic vs photocatalytic removal of organic water contaminants
Authors: Ioannis Papagiannis, George Avgouropoulos and Panagiotis Lianos
Affiliation: University of Patras, Greece
Abstract: Organic visible and near-UV light absorbing water contaminants have been photocatalytically degraded using titania photocatalyst. Mesoporous titania films were deposited on fluorine doped tin oxide (FTO) transparent electrodes and were used either free or under electric bias, which is known to accelerate decomposition rate. Emphasis has been placed on the structure of the film, its crystallinity, specific surface as well as the value of the applied bias. In addition, degradation rate was studied with respect to the nature and the concentration of the employed electrolyte. The results were referenced to model dyes, for example, methylene blue, but they may be extended to other categories such as pharmaceuticals or pesticides.

Title: De-ethylation and cleavage of Rhodamine B by zirconium phosphate/silver bromide composite photocatalyst
Authors:
Monica Pica1*, Silvia Calzuola1, Anna Donnadio1, Pier Luigi Gentili2, Morena Nocchetti1 and Mario Casciola2*
Affiliation:
1Department of Pharmaceutical Sciences, University of Perugia, Via del Liceo, 1, 06123 Perugia (Italy)
2University of Perugia, Department of Chemistry, Biology and Biotechnologies, Via Elce di Sotto, 8, 06123 Perugia (Italy)
*Corresponding authors:  [email protected]; [email protected]
Abstract: A composite heterogeneous photocatalyst based on silver bromide was prepared by reaction of silver exchanged zirconium phosphate (ZrP) and HBr. The ZrP/AgBr composite containing 53 wt% AgBr was tested in the photocatalytic degradation of Rhodamine B (RhB), exhibiting, with respect to pure AgBr, higher catalytic activity. As a matter of fact, the time needed to achieve a percentage of chromofore cleavage of about 90 % was 3 min for the composite vs 30 min needed for pure AgBr. The UV-Vis spectra of RhB solution, recorded at different irradiation times, were deconvoluted, in order to have information about the concentration of the species formed by de-ethylation and cleavege processes during photocatalysis, and to go insight of the degradation mechanism. The smaller particle size of AgBr in the composite, with respect to the pure AgBr sample, enhanced the dye adsorption onto the solid catalyst and, in turn, contributed to improve its catalytic activity. Moreover, the presence of ZrP did not alter the mechanism of the photodegradation process. The ZrP/AgBr turned out to be stable for at least three consecutive cycles.

Title: Fluorinated and platinized Titania as effective materials in the photocatalytic treatment of dyestuffs and stained wastewater coming from handicrafts factories
Abstract:
In this study, commercial P25 and lab prepared TiO2 were modified by fluorination and platinum photodeposition. The catalysts thus obtained were extensively characterized and it was found that these modifications lead to improve the optical and photocatalytic properties of Titania. The materials prepared were tested in the photocatalytic degradation of different organic dyestuffs: methylene blue (MB) and commercial anilines employed in the staining of natural fibers. Photocatalysis was also studied in this work as an eco-friendly treatment of wastewater coming from Colombian handicrafts factories. Platinized and fluorinated commercial Titania (Pt-F-P25) has shown the best photocatalytic activity in the MB degradation; on the contrary, in the case of the anilines the highest degradation was obtained over fluorinated P25 (F-P25). These results can be explained by differences observed in the structure and in the adsorption of these dyestuffs over the photocatalysts surface. It was also found that the dyestuffs and bacterial concentration in wastewater samples noticeable decrease after treatment by using F- P25 as photocatalyst.

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