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18 pages, 7781 KiB

Open AccessArticle

Photo-Fenton-Like Treatment of Municipal Wastewater

by Yerkanat N. Kanafin, Ardak Makhatova, Vasilios Zarikas, Elizabeth Arkhangelsky and Stavros G. Poulopoulos

Catalysts 2021, 11(10), 1206; https://doi.org/10.3390/catal11101206 - 8 Oct 2021

Cited by 14 | Viewed by 2345

Abstract

In this work, the photochemical treatment of a real municipal wastewater using a persulfate-driven photo-Fenton-like process was studied. The wastewater treatment efficiency was evaluated in terms of total carbon (TC), total organic carbon (TOC) and total nitrogen (TN) removal. Response surface methodology (RSM) [...] Read more.

In this work, the photochemical treatment of a real municipal wastewater using a persulfate-driven photo-Fenton-like process was studied. The wastewater treatment efficiency was evaluated in terms of total carbon (TC), total organic carbon (TOC) and total nitrogen (TN) removal. Response surface methodology (RSM) in conjunction Box-Behnken design (BBD) and multilayer artificial neural network (ANN) have been utilized for the optimization of the treatment process. The effects of four independent factors such as reaction time, pH, K₂S₂O₈ concentration and K₂S₂O₈/Fe²⁺ molar ratio on the TC, TOC and TN removal have been investigated. The process significant factors have been determined implementing Analysis of Variance (ANOVA). Both RSM and ANN accurately found the optimum conditions for the maximum removal of TOC (100% and 98.7%, theoretically), which resulted in complete mineralization of TOC at the reaction time of 106.06 min, pH of 7.7, persulfate concentration of 30 mM and K₂S₂O₈/Fe²⁺ molar ratio of 7.5 for RSM and at the reaction time of 104.93 min, pH of 7.7, persulfate concentration of 30 mM and K₂S₂O₈/Fe²⁺ molar ratio of 9.57 for ANN. On the contrary, the attempts to find the optimal conditions for the maximum TC and TN removal using statistical, and neural network models were not successful. Full article

(This article belongs to the Special Issue New Trends in Photocatalysis: Photocatalytic Materials and Applications)

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14 pages, 4721 KiB

Open AccessCommunication

Valence Regulation of Ultrathin Cerium Vanadate Nanosheets for Enhanced Photocatalytic CO₂ Reduction to CO

by Lujia Ding, Qiutong Han, Hong Lu, Yong Yang, Gang Lu, Hui Zhang, Xueqin Ran, Yingdong Xia, Ping Li, Yonghua Chen and Yong Zhou

Catalysts 2021, 11(9), 1115; https://doi.org/10.3390/catal11091115 - 16 Sep 2021

Cited by 12 | Viewed by 2558

Abstract

Atomic valence state regulation is an advantageous approach for improving photocatalytic efficiency and product selectivity. However, it is difficult to precisely control the ratio of the different valence states on the surface and the relationship between the surface valence change and catalytic efficiency [...] Read more.

Atomic valence state regulation is an advantageous approach for improving photocatalytic efficiency and product selectivity. However, it is difficult to precisely control the ratio of the different valence states on the surface and the relationship between the surface valence change and catalytic efficiency in the photocatalytic reaction process is unclear. Herein, CeVO₄ ultrathin nanosheets were fabricated by one-step solvothermal method with ethanolamine (MEA) as the structure-directing agent. The ratio of the concentrations of intrinsic Ce⁴⁺ and Ce³⁺ ions is precisely modulated from 19.82:100 to 13.33:100 changed by the volume of MEA added without morphology modification. The photocatalytic efficiency increases as the concentrations of intrinsic Ce⁴⁺ and Ce³⁺ ions decrease and CV3 (prepared with 3 mL of MEA) shows the highest CO generation rate approximately 6 and 14 times larger than CV (prepared without MEA) and CV1 (prepared with 1 mL of MEA), respectively, in the photocatalytic CO₂ reduction. Interestingly, about 6.8% photo-induced Ce⁴⁺ ions were generated on the surface of the catalysts during the photocatalytic CO₂ reduction without any phase and morphology changes for CV3. The photocatalytic reaction mechanism is proposed considering the intrinsic and photo-induced Ce⁴⁺ ions to obtain efficient photocatalysts. Full article

(This article belongs to the Special Issue New Trends in Photocatalysis: Photocatalytic Materials and Applications)

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19 pages, 4972 KiB

Open AccessArticle

Enhanced Visible Light Photocatalytic Degradation of Methylene Blue by CdS-ZnS-BiPO₄ Nanocomposites Prepared by a Solvent-Assisted Heating Method

by Hsin-Chan Tsai, Yu-Hui Peng, Po-Yu Wen, Tsunghsueh Wu and Yang-Wei Lin

Catalysts 2021, 11(9), 1095; https://doi.org/10.3390/catal11091095 - 11 Sep 2021

Cited by 10 | Viewed by 2400

Abstract

In this study, a ternary CdS-ZnS-BiPO₄ nanocomposite, synthesized by a solvent-assisted heating method, demonstrated the highest visible light-induced photocatalysis towards the degradation of methylene blue (MB) when comparing with BiPO₄, CdS-BiPO₄, and ZnS-BiPO₄. Transmission electron microscopy [...] Read more.

In this study, a ternary CdS-ZnS-BiPO₄ nanocomposite, synthesized by a solvent-assisted heating method, demonstrated the highest visible light-induced photocatalysis towards the degradation of methylene blue (MB) when comparing with BiPO₄, CdS-BiPO₄, and ZnS-BiPO₄. Transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and UV-Vis diffuse reflectance spectroscopy (UV-vis DRS) were used to characterize the prepared nanocomposites. From UV-DRS results, the energy band gap of the prepared BiPO₄ structures was 4.51 eV. When CdS nanoparticles were deposited on BiPO₄ surface by a solvent-assisted heating method, the prepared nanocomposites exhibited visible light-responsive photocatalytic degradation toward MB (20 ppm). At a molar ratio of Cd to Zn as 1:7, the prepared CdS-ZnS-BiPO₄ nanocomposites exhibited the best photocatalytic activity in degrading 95% of MB dyes, out-performing pure BiPO₄, CdS-BiPO₄, and ZnS-BiPO₄ due to its enhanced charge separation efficiency and the lowered carrier recombination from the efficient p-n junction of unprecedented ternary composites. The investigations on mechanism conclude that the major reactive species responsible for MB degradation are holes and oxygen radicals. For practicality, the degradation efficiency for different dyestuff (Fast Green FCF, Rhodamine 6G, Acid Blue 1, methyl orange, and methyl red) degradation in the different water matrix samples (pond water, seawater, and lake water) by the prepared CdS-ZnS-BiPO₄ nanocomposites was evaluated. Full article

(This article belongs to the Special Issue New Trends in Photocatalysis: Photocatalytic Materials and Applications)

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9 pages, 7545 KiB

Open AccessArticle

Refractory Metal Oxide–Doped Titanate Nanotubes: Synthesis and Photocatalytic Activity under UV/Visible Light Range

by Min-Sang Kim, Hyun-Joo Choi, Tohru Sekino, Young-Do Kim and Se-Hoon Kim

Catalysts 2021, 11(8), 987; https://doi.org/10.3390/catal11080987 - 18 Aug 2021

Cited by 1 | Viewed by 2042

Abstract

This study synthesized refractory metal-oxide-doped titanate nanotubes (TNTs) using a hydrothermal process and investigated their photocatalytic activity under ultraviolet and visible light irradiation. Refractory metal doping ions such as Mo⁶⁺ and W⁶⁺ can be supplied from molybdenum oxide and tungsten oxide [...] Read more.

This study synthesized refractory metal-oxide-doped titanate nanotubes (TNTs) using a hydrothermal process and investigated their photocatalytic activity under ultraviolet and visible light irradiation. Refractory metal doping ions such as Mo⁶⁺ and W⁶⁺ can be supplied from molybdenum oxide and tungsten oxide sources. The refractory metal-doped TNT may act as an electron trap or enhance the adsorption capacity, which increases the number of active sites and promotes separation efficiency. Full article

(This article belongs to the Special Issue New Trends in Photocatalysis: Photocatalytic Materials and Applications)

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14 pages, 4281 KiB

Open AccessFeature PaperArticle

Photocatalytic Degradation of Valsartan by MoS₂/BiOCl Heterojunctions

by Eleni Grilla, Maria Nefeli Kagialari, Athanasia Petala, Zacharias Frontistis and Dionissios Mantzavinos

Catalysts 2021, 11(6), 650; https://doi.org/10.3390/catal11060650 - 21 May 2021

Cited by 8 | Viewed by 2940

Abstract

In the present study, the removal of valsartan (VLS), an antihypertensive agent, under simulated solar radiation with the use of molybdenum sulfide-bismuth oxychloride composites (MoS₂/BiOCl), of variable MoS₂ content (0.1–10.0 wt.%) was investigated. The physicochemical properties of the photocatalysts were [...] Read more.

In the present study, the removal of valsartan (VLS), an antihypertensive agent, under simulated solar radiation with the use of molybdenum sulfide-bismuth oxychloride composites (MoS₂/BiOCl), of variable MoS₂ content (0.1–10.0 wt.%) was investigated. The physicochemical properties of the photocatalysts were examined by XRD, DRS, BET and TEM/HRTEM. Preliminary tests were conducted to examine the photocatalytic efficiency of the synthesized MoS₂/BiOCl composites towards VLS degradation in ultrapure water (UPW). It was found that the activity of pure BiOCl is improved with the addition of MoS₂. The degradation rate was maximized with the use of the catalyst containing 0.25 wt.% MoS₂. It was also found that the increase in catalyst concentration (50–1000 mg/L) enhances VLS degradation. It was found that VLS removal decreased by increasing VLS concentration. The effect of the water matrix on VLS removal was studied by carrying out experiments in real and synthetic water matrices. VLS degradation in UPW was faster than in bottled water (BW) and wastewater (WW), mainly due to the existence of organic matter in real aqueous media. Lastly, 0.25 wt.% MoS₂/BiOCl showed great stability after 360 min of irradiation, serving as a promising catalyst for water remediation of emerging contaminants under solar irradiation. Full article

(This article belongs to the Special Issue New Trends in Photocatalysis: Photocatalytic Materials and Applications)

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12 pages, 3703 KiB

Open AccessArticle

Immobilization of TiO₂ Nanoparticles in Hydrogels Based on Poly(methyl acrylate) and Succinamide Acid for the Photodegradation of Organic Dyes

by Xiaomeng You, Hailong Huang, Ran Zhang, Zhongli Yang, Min Xu, Xuelu Wang and Yefeng Yao

Catalysts 2021, 11(5), 613; https://doi.org/10.3390/catal11050613 - 11 May 2021

Cited by 11 | Viewed by 2825

Abstract

Hydrogels have excellent properties that make them ideally suited as host matrices for the immobilization of photoreactive materials such as TiO₂ nanoparticles that serve as catalysts in the photodegradation of organic dyes, which is of great importance in practical water pollution treatment [...] Read more.

Hydrogels have excellent properties that make them ideally suited as host matrices for the immobilization of photoreactive materials such as TiO₂ nanoparticles that serve as catalysts in the photodegradation of organic dyes, which is of great importance in practical water pollution treatment applications. However, the application of hydrogels for this purpose remains poorly studied. The present study addresses this issue by developing two types of hydrogels based on poly(methyl acrylate) and succinamide acid with embedded TiO₂ nanoparticles for use as photocatalysts in the photodegradation of organic dyes. The results of the analysis demonstrate that the TiO₂ nanoparticles are distributed uniformly in the hydrogel matrices, and the hydrogels maintain their original structures after use. The photodegradation efficiencies of the developed TiO₂-hydrogels are demonstrated to be reasonably close to that of freely distributed TiO₂ nanoparticles in solution for four different organic dyes. In addition, the results of degradation-regeneration cycling tests demonstrate that immobilizing the TiO₂ nanoparticles into the hydrogels greatly reduces their loss during utilization, and the photocatalysts can be easily reused. In fact, the two TiO₂-hydrogels retain reasonably high photocatalytic degradation performance after four degradation-regeneration cycles. Full article

(This article belongs to the Special Issue New Trends in Photocatalysis: Photocatalytic Materials and Applications)

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22 pages, 5769 KiB

Open AccessArticle

Photocatalytic Properties of Core-Shell Structured Wool-TiO₂ Hybrid Composite Powders

by Haoshuai Gu, Hui Zhang, Xinyue Zhang, Yani Guo, Limeng Yang, Hailiang Wu and Ningtao Mao

Catalysts 2021, 11(1), 12; https://doi.org/10.3390/catal11010012 - 24 Dec 2020

Cited by 13 | Viewed by 2431

Abstract

In this study, a special core–shell structured wool-TiO₂ (WT) hybrid composite powder also having TiO₂ nanoparticles incorporated inside cortical cells was reported. The wool pallets were pulverized from wool fibers using vibration-assisted ball milling technique and the WT powders having mesopores [...] Read more.

In this study, a special core–shell structured wool-TiO₂ (WT) hybrid composite powder also having TiO₂ nanoparticles incorporated inside cortical cells was reported. The wool pallets were pulverized from wool fibers using vibration-assisted ball milling technique and the WT powders having mesopores and macropores were produced in hydrothermal process. Experimental results indicated that the infiltrated TiO₂ nanoparticles were amorphous structure, while the coated TiO₂ nanoparticles were anatase phase structure. The crystallized TiO₂ nanoparticles were grafted with wool pallets by the N−Ti⁴⁺/S−Ti⁴⁺/O−Ti⁴⁺ bonds. The BET surface area was measured as 153.5 m²/g and the particle sizes were in the 600–3600 nm and 4000–6500 nm ranges. The main reactive radical species of the WT powders were holes, and •O₂⁻, ¹O₂, and •OH were also involved in the photodegradation of MB dye under visible light irradiation. The experimental parameters for photodegradation of MB dye solution were optimized as follows: 0.25 g/L of WT powders was added in 40 mL of 3 mg/L MB dye solution containing 50 mL/L H₂O₂, which resulted in the increases of COD value of degraded MB dye solution up to 916.9 mg/L at 120 min. The WT powders could be used for repeatedly photodegradation of both anionic and cationic dyes. Full article

(This article belongs to the Special Issue New Trends in Photocatalysis: Photocatalytic Materials and Applications)

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Review

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26 pages, 3049 KiB

Open AccessFeature PaperReview

Photocatalytic Applications in Wastewater and Air Treatment: A Patent Review (2010–2020)

by Marica Muscetta and Danilo Russo

Catalysts 2021, 11(7), 834; https://doi.org/10.3390/catal11070834 - 9 Jul 2021

Cited by 25 | Viewed by 4925

Abstract

In this work, we reviewed the most significant patents of the last decade (2010–2020) in the fields of water and air photocatalytic treatment. Patents were discussed by identifying the recurrent addressed issues and presenting the proposed solutions. Adoption of TiO₂ and/or modified-TiO [...] Read more.

In this work, we reviewed the most significant patents of the last decade (2010–2020) in the fields of water and air photocatalytic treatment. Patents were discussed by identifying the recurrent addressed issues and presenting the proposed solutions. Adoption of TiO₂ and/or modified-TiO₂-based material is still the most common choice of inventors, whereas many patents focus on the design of the plants/devices to improve efficiency of photocatalytic treatment by improving light utilization and contact between the phases. The review also highlights issues deriving from specific applications and outlines future trends in the field, such as the need for standardized testing and digitalization of monitoring and control. Full article

(This article belongs to the Special Issue New Trends in Photocatalysis: Photocatalytic Materials and Applications)

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