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Photocatalytic optical fibers are promising for the degradation of gaseous and volatile pollutants in air due to their high specific surface area, high light utilization efficiency, easy regeneration, and sustainability. In particular, photocatalytic optical fibers have proven highly useful for the removal and conversion of different kinds of air pollutants in air. However, these fibers suffer from low photocatalytic degradation efficiencies. In this review, we have focused on introducing photocatalytic quartz optical fibers and photocatalytic plastic optical fibers for the degradation and transformation of gas-phase air pollutants. The principle of photocatalytic optical fibers and main methods for improving their photocatalytic and light utilization efficiencies based on semiconductor photocatalytic coatings are summarized. Moreover, the Langmuir-Hinshelwood kinetic rate equation was summarized to analyze the photocatalytic reduction of gaseous pollutants. Finally, an outlook on the future of photocatalytic optical fibers toward the removal and conversion of gaseous air pollutants is discussed.

Photocatalytic technology is the recent investigation focus because of the wide applications in sewage disposal and new energy generation. In this paper, the optical and photocatalytic properties of TiO2 NTAs were enhanced by the hydrothermal deposition of CuBi2O4 by regulating the precursor concentration. The results indicated that the precursor concentration played remarkable influences on the morphology and photocatalytic ability. The mild reagent concentration was in favor of super-thin CuBi2O4 nanosheet formation. CuBi2O4/TiO2 NTAs with high reagent concentration exhibited high photocurrent and hydrogen production, and showed outstanding performance in the removal of organic dyes and heavy metal ions. The free radical production and the photocatalytic progress were introduced in detail. The high photocatalytic activity exhibits prospective foreground in industrial waste water treatment and novel energy resource development.

Preparation of bismuth oxybromide (BiOBr) photocatalyst via PVP-assisted solvothermal method has been demonstrated. The PVP capping agent plays an important role in controlling morphological structure, specific surface area and photoactivity. The PVP capped BiOBr provides 94 % and 99.8 % removal of ofloxacin (OFL) and norfloxacin (NOR) antibiotics under visible light illumination. The enhanced photoactivity of the PVP capped BiOBr is due to the flower-like microstructures with high surface area and the suppression of electron-hole pairs recombination at the interfaces. Photogenerated hole and electron play the key role in degradation of the antibiotics. The photocatalyst retains its efficiency after the fifth run indicating structural stability and reusability. The prepared PVP capped BiOBr photocatalyst shows high potential for environmental protection. The present finding offers a new avenue for fabrication of the visible-light-responsive catalyst for detoxification of antibiotics in wastewater.

Herein, a simple, highly efficient and stable MoS2 nanobox embedded graphitic-C3N4@TiO2 (g-CN@TiO2) nanoarchitecture was synthesized by a facile solvothermal approach. The nano-hybrid photocatalyst was constructed by TiO2 nanoparticles anchored on the surface of g-CN nanosheets. Then highly crystalline three-dimensional porous MoS2 nanobox was homogeneously distributed on the g-CN@TiO2 surface. The g-CN@TiO2/MoS2 hybrid achieved a high photocatalytic degradation efficiency of 97.5% for methylene blue (MB) dye pollutant under visible-light irradiant in an hour which was much better than TiO2@MoS2, g-CN@TiO2, MoS2, TiO2 and g-CN. Furthermore, the reaction rate (k) value of g-CN@TiO2/MoS2 for MB dye is as high as 3.18 X 10-2 min−1, which is ~ 2.65 times better than those of g-CN@TiO2 and MoS2. This work presents a rational structure design, interfacial construction and suitable band gap strategy to synthesize advanced nano-hybrid photocatalyst for degradation of organic pollutant with excellent performance and long-term stability.

Water serves as a key component in the basis of life to function and evolve unceasingly. Excessive deterioration of fresh water resources through discarding enormous amounts of dye effluents is becoming a problem of concern. In this work we report a conventional solid-state technique improved with choline chloride: urea DES medium in 1:2 ratio for synthesizing pure calcium titanate (CTO) and lanthanum doped calcium titanate (LaxCa1-xTiO3; x = 0.0 and 0.5). Both the materials were subjected to photocatalytically degrade reactive dyes RB5, RR198 and RY145. La-doped calcium titanate showed effective degradation efficiency when compared to the pure calcium titanate. On increasing the concentration of the dye, the efficiency of degradation declined gradually. Also, the efficiency was assessed to be greatest for RY145 followed by RR198 and lastly RB5. Efficiency dependence on different pH exposed the enhanced degradation in acidic medium and comparatively lowered pH in basic medium. Recyclability was highly satisfying and promising to validate the real-time applicability of the catalyst.

Antibiotic pollution is one of the major issues confronting human. The photocatalytic technology has been focused due to its energy conservation and environmental protection. However, semiconductor photocatalysts have some problems, such as low light utilization, carrier recombination and so on. Constructing a heterojunction can effectively solve these problems. Herein, a new heterostructure of WO3/Bi2MoO6 with core-shell structure were successfully synthesized. The properties of the heterojunction were fully characterized. Subsequently, the visible light catalytic effect of the complex was studied by degrading antibiotics. Compared with other antibiotics, this heterojunction has the best photocatalytic degradation effect on tetracycline hydrochloride. The photodegradation efficiency for tetracycline hydrochloride of complex is 157 times and 5 times than that of pure WO3 and Bi2MoO6 respectively. This is due to the combination of materials that promotes the separation of photogenerated electrons and holes, and extends their lifetime. Finally, a possible photocatalytic mechanism is proposed.

Purpose Dyeing and printing are important steps in textile manufacturing. After the process completion, these dyes are released in the effluent. These dyes impart an unacceptable appearance but are also toxic to the soil and water bodies. The present research has been carried out to study the rate of photocatalytic degradation of an azo dye, namely, CI Direct Green 26, using titania nanoparticles under ultra violet (UV) irradiation as a function of temperature and time. Azo dyes account for the majority of all dyestuffs are produced and extensively used in the textile, paper, food, leather, cosmetics and pharmaceutical industries. Titania nanoparticles have been found to successfully degrade these dyes in the presence of UV light. The purpose of the present paper was to study the photodegradation of azo dyes using titania nanoparticles at different temperatures and time periods. Design/methodology/approach Titania nanoparticle concentration of 0.1% (w/v) was dispersed in distilled water by sonication for 1 h in sonication bath. The of rate of degradation of Direct Green 26 dye in the titania nanoparticle dispersion, under UV-A exposure was studied at different temperatures ranging from 25°C to 65 °C for time periods ranging from 1 h to 6 h. Photocatalytic degradation tests were performed in a specially designed UV reactor chamber. Raman spectroscopy of Titania nanoparticles, dye and titania/dye mixture before and after UV exposure was carried out using Confocal Laser Dispersion Raman Microscope (Renishaw, UK) with 785 nm excitation laser. Findings Titanium dioxide is an efficient photocatalyst for decolourisation of direct dye. The photodegradation of the direct Green dye was found to follow the pseudo first-order reaction. The Arrhenius activation energy was found to be 24.8 kJ/mol with A value of 0.0013 for the photocatalytic degradation of the dye. Raman spectroscopy also confirmed the adsorption of dye on titania nanoparticle and its complete degradation on exposure to UV light. Practical implications This research highlights the application of titania nanoparticles for the effective degradation of dye in the effluent from textiles, clothing, paper and any kind of dyeing process. Azo dyes account for the majority of all dyestuffs are produced and extensively used in the textile, paper, food, leather, cosmetics and pharmaceutical industries. Titania nanoparticles have been found to successfully degrade these dyes in the presence of UV light which can be very beneficial for the effluent treatment plants in textile and other industries. Originality/value Azo dyes are one of the harmful pollutants released in textile waste water. The degradation and removal of the coloured waste in the textile effluent is an important environmental concern and needs to be investigated. The research is one of the first to investigate and understand the mechanism of the degradation of an azo dye in the presence of titania nanoparticles by Raman spectroscopy.

This study was supported by the Tomsk State University competitiveness improvement programme. The work was carried out within the state task of The RF Ministry of Education and Science (No 0365-2019-0005).

The biodegradation of low-density Polyethylene (LDPE) is usually time-consuming, In the presence of Titania-nanoparticles, LDPE is photocatalytically degraded in smaller fragments afterward the bac...

In this work, Z-scheme Ag2S/Bi2O3 composites were fabricated through the precipitation of Ag2S nanoplates on the surface of Bi2O3 microrods. Consequently, Au nanoparticles were selectively deposited on the Ag2S nanoplates surface to obtain. Au-Ag2S/Bi2O3 composites using near-infrared light photodeposition method. The characterization results indicate that the Ag2S nanoplates were uniformly anchored on Bi2O3 surface, and Au nanoparticles were highly dispersed on the surface of Ag2S nanoplate instead of Bi2O3. Acid orange 7 (AO7), Rhodamine B (RhB) and Cr(VI) were chosen as model reactant for the evaluation of photocatalytic degradation and reduction activity of the products under simulated sunlight irradiation. After the decoration of Ag2S nanoplates, the photocatalytic activity of Ag2S/Bi2O3 is much higher than that of bare Bi2O3, and the optimal catalytic efficiency is achieved by 12 %Ag2S/Bi2O3 sample. More importantly, the photocatalytic activity of 12 %Ag2S/Bi2O3 sample can be further enhanced by the selective decoration Au nanoparticles on the Ag2S nanoplates. Among the ternary composites, 2Au-12 %Ag2S/Bi2O3 sample with the Au content of 2% exhibits highest catalytic efficiency for 60 min (AO7: 96%; RhB: 56%; Cr(VI): 65%). The possible mechanism for the improvement of the photocatalytic activity of Bi2O3 by Ag2S and Au decoration was proposed.

Caffeine is a refractory pollutant of emerging concern that evades conventional waste-water treatment techniques. Here, we report the synthesis of visible light responsive perovskite structured LaMnO­3 photocatalyst using modified Pechini method and utilized it as an efficient photocatalyst for caffeine degradation. XRD, BET, UV-Vis, NH3-TPD, and SEM were used to characterize the photocatalyst. Response surface methodology using Central composite design was used to investigate the effect of three operational variables; catalyst dosage, initial caffeine concentration and pH on the caffeine photocatalytic degradation efficiency. The functional relationship between these operational variables and caffeine photocatalytic degradation efficiency was established be a second order polynomial model. The results of the response surface analysis indicate caffeine degradation efficiency is most significantly affected by catalyst dosage and pH. The optimal values of operational obtained by response surface optimization were found be 3.5 g/L for catalyst dosage, 7.9 and 44.6 mg/L for pH and initial caffeine concentration respectively given the caffeine degradation efficiency of 93.9%.

An effective path to synthesize Znx Cd1-x S quantum dots (ZCS QDs) in aqueous phase at room temperature has remained relatively unexplored. Here, we developed a room-temperature, aqueous-phase approach to ZCS QDs, using 3-mercaptopropionic acid (MPA) to adjust the pH of the reaction precursor solution to regulate the competition between sulfur source and hydroxyl group, and realize the large-scale preparation of water-soluble ZCS QDs photocatalyst at room temperature. Without recombination with other materials, and only by regulating the ratio of pH, excess sulfur sources and Zn/Cd, the photocatalytic degradation of rhodamine B (RhB) can reach 98% within 1 min, showing high photocatalytic activity. ZCS QDs show high stability and recoverability, and are expected to be able to deal with organic pollutants on a large scale. This study provides a new idea for the preparation of other QDs at room temperature.

The phase transition process of a photocatalytic system from NaBiO3·2H2O to BiO2−x has been investigated to understand the important factors that affect photocatalytic performance in a composite system. It is found that a proper amount of BiO2−x on the surface of NaBiO3·2H2O could effectively suppress the electron/hole recombination and increase the exposed reactive sites for photocatalytic reaction. A fully covered BiO2−x on NaBiO3·2H2O results in a dramatical decrease of photocatalytic degradation of dye. An over long hydrothermal process can result in BiO2−x with reduced oxygen vacancies, which degrades the photocatalytic activity. Furthermore, the photocatalytic reduction ability of CO2 conversion has been investigated, indicating that the surface activity to different reactants also directly affects the catalytic performance. The investigation of the gradient phase transition process presents a clear guidance to construct a desired photocatalytic system, in addition to selecting gradient materials with suitable bandgap structure and a morphology with different fraction and distribution of each component. The defect evolution of each component during construction of a composite is also an important factor that should be optimized and considered in making a composite to achieve high photocatalytic efficiency.

Cobalt aluminate/carbon composite nanoparticles have been synthesised by utilising an auto-combustion method using glycine as an inexpensive fuel. The products were analysed by various techniques s...

The disposal of dye-contaminated wastewater is a major concern around the world for which a variety of techniques are used for its treatment. The photocatalytic treatment of dye-contaminated wastewater is one of the treatment methods. Semiconductor-assisted photocatalytic treatment of dye-contaminated wastewater has gained pronounced attention recently. This review outlines the recent advancements in the photocatalytic treatment of dye-contaminated wastewater. The photocatalytic degradation of dyes follows three types of mechanisms: (1) dye sensitization through charge injection, (2) indirect dye degradation through oxidation/reduction, and (3) direct photolysis of dye. Several experimental parameters like initial concentration of dyes, pH, and catalyst dosage significantly affect the photocatalytic degradation of dyes. The photocatalytic materials can be categorized into three generations. The single-component (e.g., ZnO, TiO2) and multiple component semiconductor metal oxides (e.g., ZnO–TiO2, Bi2O3–ZnO) are categorized as first-generation and second-generation photocatalysts, respectively. The photocatalysts dispersed on an inert solid substrate (e.g., Ag–Al2O3, ZnO–C) are classified as third-generation photocatalysts. Finally, we reviewed the challenges that affect the photocatalytic degradation of dyes.

TiO2 pillared clay was prepared by intercalation of titan polyoxocation into interlamelar space of an Algerian montmorillonite and used for the photocatalytic degradation of the linuron herbicide as a target pollutant in aqueous solution. The TiO2 pillared montmorillonite (Mont-TiO2) was characterized by X-ray photoelectron spectroscopy (XPS), X-Ray diffraction (XRD), X-Ray fluorescence (XRF), scanning electronic microscopy (SEM), thermogravimetry and differential thermal analysis (TG-DTA), Fourier transformed infra-red (FT-IR), specific area and porosity determinations. This physicochemical characterization pointed to successful TiO2 pillaring of the clay. The prepared material has porous structure and exhibit a good thermal stability as indicated by its surface area after calcination by microwave. The effects of operating parameters such as catalyst loading, initial pH of the solution and the pollutant concentration on the photocatalytic efficiency and COD removal were evaluated. Under initial pH of the solution around seven, pollutant concentration of 10 mg/L and 2.5 g/L of catalyst at room temperature, the degradation efficiency and COD removal of linuron was best then the other operating conditions. It was observed that operational parameters play a major role in the photocatalytic degradation process. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

NiFe2O4 nanoparticles had been successfully synthesized by solution combustion method using urea fuel (organic precursor). The synthesized NiFe2O4 were characterized by X-ray diffraction (XRD), Scanning electron microscopy-Electron Dispersive X-ray Spectroscopy (SEM-EDs), Transmission Electron Microscopy (TEM), Fourier Transform Infra-Red (FTIR), Vibrating Sample Magnetometer (VSM), UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis DRS), and Point of Zero Charge (pHpzc). NiFe2O4 nanoparticles irradiated with visible light were employed to degrade Congo red dye with the following variable: solution pH (3–8), H2O2 concentration (0.5–3 mM), and Congo red concentration (100–600 mg/L). XRD analysis results showed that the NiFe2O4 nanoparticles had a cubic spinel structure. The particle sizes are in the range of 10–40 nm. The magnetic properties of NiFe2O4 nanoparticles determined using VSM showed a magnetization saturation value of 47.32 emu/g. UV-Vis DRS analysis indicated that NiFe2O4 nanoparticles had an optical band gap of 1.97 eV. The success of synthesis was also proven by the EDS analysis results, which showed that the synthesized NiFe2O4 nanoparticles composed of Ni, Fe, and O elements. The removal efficiency of Congo red dye was 96.80% at the following optimum conditions: solution pH of 5.0, H2O2 concentration of 2 mM, Congo red dye concentration of 100 mg/L, and contact time of 60 min. The study of the photodegradation kinetics follows a pseudo-first order reaction with a rate constant value of 0.0853 min−1. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Photocatalytic degradation is an upcoming technique for the removal of organic pollutants from wastewater. This topic attracts increasing interest due to its potential of utilizing “freely” availab...

This paper describes a novel process for the synthesis of TiO2 from titanium slag, which is realized via roasting titanium slag with KHSO4, acid leaching and hydrolysis. The results showed that the optimum conditions were a mass ratio of KHSO4 to titanium slag of 6, a temperature of 600 oC for 1,5 hours. Besides, this study investigated the possibility of synthesized TiO2 for photocatalytic degradation of methylene blue.

The novel FeS2/ZnO nanocomposites was synthesised by a chemical precipitation rout. The optical and structure properties of the synthesised catalysts were characterised by X-ray diffraction, energy...

In this, work, a series of REVO4 (RE = La, Pr, Nd) nanoparticles were successfully fabricated by the hydrothermal method. The as-synthesized REVO4 nanoparticles were characterized by various techniques of X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). The photocatalytic activities of obtained products were investigated by photodegradation of moderacid red RS and direct yellow GX under visible light. The NdVO4 photocatalyst showed higher discoloration of organic dyes than LaVO4 and PrVO4. About 64% moderacid red RS was degraded within 150 minutes catalyzed by the catalyst NdVO4.

Photocatalysis is regarded as one of the most promising technologies to remove organic contaminants. At present, most of the covalent organic frameworks (COFs) used as photocatalysts are connected by imine or borate bonds, which have relatively low stability and relatively poor π-delocalization. Herein, we report, for the first time, vinylene-linked COFs constructed by various diacetylene and triazine moieties for photocatalytic degradation of organic contaminants and disinfection of bacteria. The pioneering introduction of diacetylene moieties not only enhances conjugated π-electrons delocalization but also optimizes the electronic band structures that significantly improve photocatalytic activity. Therefore, the vinylene-bridged COFs have excellent photocatalytic activity with ultrahigh stability and great π-electron delocalization, thus exhibiting ultrafast photocatalytic degradation efficiency for phenol and norfloxacin (96%, within 15 min). Our work provides a strong basis for the rational regulation of the chemical structure of COFs to enhance their photocatalytic activity, thus broadening the application of COFs in photocatalysis.

Background: Microreactor devices have attracted increasing attention over the last years due to their high surface-to-volume ratio, which ensures a high heat and mass transfer, short molecular diffusion distance and greater spatial illumination homogeneity compared to the traditional reactors. Objective: The aim of this study was to model the kinetics of photo-degradation of 2-propanol over TiO2-based thin films in a gas-phase batch-reactor and simulate their performance in a microreactor device. Methods: The reaction was carried out in a gas-phase batch-reactor, assessing the reactivity of singlelayer nitrogen (N)-doped TiO2 and a bilayer consisting of N-doped TiO2 as a bottom layer and copper (Cu)-doped TiO2 as a top layer. The kinetics of the photocatalytic process was modelled by Langmuir– Hinshelwood (LH) model. The constants obtained from the LH model were used to simulate the performance of the photocatalysts in a microreactor, operating in a continuous flow mode and investigating the effect of the volumetric flow rate (Q), initial concentration of pollutant (Co), number of microchannels (n) and microchannel length (l) on the photo-degradation of 2-propanol. Results: N-Cu-TiO2 exhibited a higher reactivity but a lower adsorption ability towards the target pollutant compared to N-TiO2. To maximize and leverage the advantages of a microreactor, optimal operating conditions for a continuous flow mode, at a steady-state, should be moderately low Q and Co, long l and n that minimizes flow maldistribution in parallel. Conclusion: The findings in this work could serve as a basis to design and fabricate efficient microreactors for the removal of VOC in air purification applications.