Preparation, characterization and photocatalytic activities of boron- and cerium-codoped TiO2

NiFe2O4@B,N,F-tridoped CeO2 (NFTDNC): a mesoporous nanocatalyst in the synthesis of pyrazolopyranopyrimidine and 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives and as an adsorbent

Mesoporous materials, due to their unique textural and structural features and successful applications in different scientific areas, engrossed our curiosity to form a mesoporous nanostructure. A facile method for the formation of nickel ferrite immobilized over B,N,F tridoped mesoporous cerium oxide (CeO₂) nanostructures (NFTDNC) was designed and communicated in this report. It was characterized by thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction study (PXRD), scanning transmission electron microscopy (STEM), high-resolution transmission electron microscopy (HR-TEM), field emission gun-scanning electron microscopy (FE-SEM), vibrating sample magnetometry (VSM), photoluminescence (PL), Brunauer-Emmett-Teller (BET), energy dispersive X-ray analysis (EDX) and elemental mapping, UV-visible spectroscopy (UV-VIS) and Fourier transform infrared spectroscopy (FT-IR). The applications of the mesoporous nanomaterial (NFTDNC) as an adaptable heterogeneous nanocatalyst and as a phenomenal adsorbent for methyl orange (MO) dye were established. It catalyzed the formation of pyrazolopyranopyrimidine and 1H-pyrazolo[1,2-b]phthalazine-5,10-diones derivatives for the five runs. The recycled catalyst exhibited agglomeration in structural features confirmed by PXRD and HR-TEM studies. NFTDNC as an adsorbent fitted the Freundlich isotherm for the adsorption of MO dye. Moreover, it followed the linear pseudo-second-order kinetics rate equation (R² ≥ 0.98914). MO was adsorbed completely in 60 min with the NFTDNC mesoporous nanostructure.

Enhanced disinfection of E. faecalis and levofloxacin antibiotic degradation using tridoped B-Ce-Ag TiO2 photocatalysts synthesized by ecofriendly citrate EDTA complexing method

Since its use for photochemical water splitting reported first in 1972, TiO₂ is one of the most extensively studied photocatalysts for a diverse range of applications. Monodoping or codoping of the catalyst is a proven strategy to enhance the functionality of TiO₂ under solar or visible light. However, the use of three or more dopants in the development of more efficient and visible light active photocatalysts has not been investigated widely, especially for microbial disinfection. Boron/cerium/silver tridoped TiO₂ photocatalysts with curated amounts of the dopants (B = 1, 2 at.%, Ce = 0.1 at.%, Ag = 0.06 at.%), synthesized by the ecofriendly EDTA-citrate method, were evaluated for the disinfection of water using Enterococcus faecalis under UV-A irradiation and degradation of levofloxacin antibiotic under solar light. The catalyst characterization revealed that the spherical nanoparticles had a crystallite size of ~ 13 nm and bandgap energy values of 2.8-2.9 eV. 2B-0.1Ce-0.06Ag-TiO₂ is the best catalyst for microbial disinfection with a log reduction and kinetic rate constant ~ 30 and ~ 4.5 times higher than those values determined for the other codoped or monodoped catalysts, confirming an enhanced performance. Regarding levofloxacin degradation, the best performing catalyst is 1B-0.1Ce-0.06Ag-TiO₂ with degradation of 99% and 83% COD reduction in 100 min. The tridoped photocatalysts are very effective in the inactivation of Enterococcus faecalis, thus solving the problem of antimicrobial resistance in waters containing antibiotic residues.

Removal of Paracetamol from Aqueous Solutions by Photocatalytic Ozonation over TiO2-MexOy Thin Films

Analgesics and nonsteroidal anti-inflammatory drugs (NSAIDs) such as paracetamol, diclofenac, and ibuprofen are frequently encountered in surface and ground water, thereby posing a significant risk to aquatic ecosystems. Our study reports the catalytic performances of nanosystems TiO2-MexOy (Me = Ce, Sn) prepared by the sol-gel method and deposited onto glass slides by a dip-coating approach in the removal of paracetamol from aqueous solutions by catalytic ozonation. The effect of catalyst type and operation parameters on oxidation efficiency was assessed. In addition to improving this process, the present work simplifies it by avoiding the difficult step of catalyst separation. It was found that the thin films were capable of removing all pollutants from target compounds to the oxidation products.

Recent Progress on Titanium Dioxide Nanomaterials for Photocatalytic Applications

Environmental and energy problems have drawn much attention owing to rapid population growth and accelerated economic development. For instance, photocatalysis, "a green technology", plays an important role in solar-energy conversion owing to its potential to solve energy and environmental problems. Recently, many efforts have been devoted to improving visible-light photocatalytic activity by using titanium dioxide as a photocatalyst as a result of its wide range of applications in the energy and environment fields. However, fast charge recombination and an absorption edge in the UV range limit the photocatalytic efficiency of TiO₂ under visible-light irradiation. Many investigations have been undertaken to overcome the limitations of TiO₂ and, therefore, to enhance its photocatalytic activity under visible light. The present literature review focuses on different strategies used to promote the separation efficiency of electron-hole pairs and to shift the absorption edge of TiO₂ to the visible region. Current synthesis techniques used to elaborate several nanostructures of TiO₂ -based materials, recent progress in enhancing visible photocatalytic activity, and different photocatalysis applications will be discussed. On the basis of the studies reported in the literature, we believe that this review will help in the development of new strategies to improve the visible-light photocatalytic performance of TiO₂ -based materials further.

Sono-dispersion of TiO2 nanoparticles over clinoptilolite used in photocatalytic hydrogen production: Effect of ultrasound irradiation during conventional synthesis methods

Hydrogen evolution via water splitting was investigated over the sonochemically synthesized TiO₂-clinoptilolite photocomposites. To this aim, a series of photocatalysts containing 10wt% titania were prepared by impregnation and solid state dispersion (SSD) methods in the presence and absence of ultrasound irradiation. The samples were characterized by XRD, FESEM, EDX, BET, FTIR, PL and UV-vis techniques and tested for the water splitting. The characterization results indicated that ultrasound irradiation endowed the photocatalysts with uniform morphology, higher surface area and more homogenous dispersion. In addition, the analyses also exhibited less population of particle aggregates, a strong titania-support interaction and lower electron-hole pairs recombination rate. These features were more prominent when ultrasound was employed during SSD method. The TiO₂/Clinoptilolite photocatalyst prepared by the ultrasound assisted SSD method (TiO₂/CLT(US)), had more uniform active sites dispersion, high separation efficiency of electron-hole pairs and as a consequence, high surface density of active sites. The highest photocatalytic activity, 569.88 [Formula: see text] , was obtained for the TiO₂/CLT(US) sample which was about 8 times more than that of P-25 as a reference sample. Furthermore, the TiO₂/CLT(US) photocomposite as optimal photocatalyst showed sufficient reusability, making it a good choice for photocatalytic water splitting applications.

Light-Storing Photocatalyst: The Possibility of Activating Titanium Dioxide by Photoluminescence

Introduction

The aim of the present work was to analyze the possibility of creating a light-storing photocatalyst material, a system that couples a phosphorescent substrate with a titania coating. The substrate could activate the titanium dioxide coating even in condition of darkness thanks to its light emission. This improvement of absorption can be achieved because the titania semiconductor is irradiated both by the direct light and by the luminescent substrate which is activated at the same time.

Methods

TiO2-based sol-gel solutions were deposited on commercial borosilicate glasses containing 2 different phosphorescent pigments (emission peaks at 470 and 520 nm, respectively). Particular attention was paid to optimize the film-substrate adhesion by using a scratch test to evaluate the optimal temperature of the post- treatment step.

Results and discussion

The main result is that when irradiated the photoluminescent pigments allow an increase in the photocatalytic acitivity of the coatings. The pigments are able to convert the ultraviolet component of light in order to increase the amount of energy that can be absorbed by titania. Moreover, the hydrophilicity test showed that in the absence of irradiation the phosphorescent samples are characterized by a lower loss of superhydrophilicity.

Photocatalytic degradation of paraquat dichloride over CeO2-modified TiO2 nanotubes and the optimization of parameters by response surface methodology

The synthesis and surface modification of TiO₂ nanotubes with CeO₂ holding strong potential for photocatalytic organic pollutant abatement in water.

A Potential Hybrid TiO2 in Photocatalytic Seawater Desalination

Titanium dioxide (TiO2) is excellently used in various applications including wastewater treatment. It is known to have superb pigmentary properties, high adsorption in the ultraviolet (UV) region, and high stability. The objective of this paper is to study the effect of contact time of seawater desalination in the photocatalytic reaction. The hybrid TiO2 catalysts; a mixture of TiO2 and biomass ash, was synthesized via wet impregnation and calcined at 800 °C. The photocatalyst was then characterized by using Scanning Electron Microscopy (SEM) and Braunauer-Emmett-Teller (BET). The investigation was carried out in a photoreactor equipped with UV light operated for up to six hours with catalyst to seawater weight ratio of 1:400 and stirring speed of 600 rpm. The salt concentration, turbidity and pH of the water were determined prior and after the investigation. The result indicates that the salt concentration gradually decreased more than 25% as the contact time increased up to six hours. However, there is no significant change on pH value of the water. It can be concluded that the hybrid TiO2 is able to reduce the seawater salinity effectively.

Effect of the Amount of Water in the Synthesis of B-TiO2: Orange II Photodegradation

A series of boron-doped TiO2 photocatalysts (2% B-TiO2) with different water/alkoxide molar ratio were synthesized by conventional sol-gel method. The prepared samples were characterized by BET measurement, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIRS), and diffuse-reflectance UV-vis. The phase anatase was present, but unexpectedly a small amount of rutile phase was formed with low and excess water in the synthesis. Additionally it has been observed that the increase in the molar ratio of water significantly increases the values of band gap energy and the specific surface area. Results showed that degradation of Orange II azo dye increases with surface area, particle size, boron, and water content in photocatalysis. The boron species were introduced in the tricoordinated form.

Photocatalytic Degradation of Organic Pollutants: A Review

Water pollution is increasing at an ever increasing pace and the whole world is in the cancerous grip of this pollution. Various industries are discharging their untreated effluents into the nearby water resources; thus, adding to the existing water pollution to a great extent. Hence, there is a pressing demand to develop an alternate technology for wastewater treatment and in this context; photocatalysis has emerged as an Advanced Oxidation Process with green chemical approach for such a treatment. This chapter deals with photocatalytic degradation of different kinds of organic pollutants; mainly surfactants, pesticides, dyes, phenols, chloro compounds, nitrogen containing compounds etc. Mechanisms of their degradation have also been discussed with hydroxyl and allied radicals as the main active oxidizing species.

Simulated-sunlight-activated photocatalysis of methylene blue using cerium-doped SiO2/TiO2 nanostructured fibers

Cerium-doped SiO2/TiO2 nanostructured fibers were fabricated by electrospinning technology. The prepared fibers were characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Using the fibers as catalysts, photocatalytic degradation of Methylene Blue (MB) aqueous solution was carried out under simulated sunlight. The 0.2% Ce doping proved to be the optimal concentration for the doping of TiO2/SiO2, compared to other Ce-doped molar concentrations. The 0.2% Ce-doped SiO2/TiO2 fibers exhibited higher photocatalytic activity than industrial Degussa P25 and the samples doped with only Ce or SiO2. The reasons for improving the photocatalytic activity were also discussed. Several operational parameters were studied, which showed that the photocatalytic efficiency of MB was influenced by parameters such as the initial dye concentration, the initial pH, inorganic anions, and so on. In addition, the influences of an electron acceptor and a radical scavenger suggested that OH was the dominant photooxidant during the photocatalytic process. The reuse evaluation of the fibers indicated that their photocatalytic activity had good stability.

A visible light-responsive iodine-doped titanium dioxide nanosphere

I-doped titanium dioxide nanospheres (I-TNSs) were synthesized via a two-step hydrothermal synthesis route, their potential for the efficient utilization of visible light was evaluated. The prepared anatase-phase I-TNSs had a bimodal porous size distribution with a Brunauer-Emmett-Teller surface area of 76 m2/g, a crystallite size of approximately 14 nm calculated from X-ray diffraction data, and a remarkable absorption in the visible light region at wavelengths > 400 nm. The photocatalytic activity of the samples was evaluated by decoloration of Methyl Orange in aqueous solution under visible light irradiation in comparison to the iodine-doped TiO2 (I-TiO2). The I-TNSs showed higher photocatalytic efficiency compared with I-TiO2 after irradiation for 180 min even though the latter had a much greater surface area (115 m2/g). It was concluded that the surface area was not the predominant factor determining photocatalytic activity, and that the good crystallization and bimodal porous nanosphere structure were favourable for photocatalysis.

Photocatalytic activity of boron-modified titania under UV and visible-light illumination

Nanosized boron(III) oxide-doped titania was prepared by homogeneous hydrolysis of titanium oxo-sulfate with urea in aqueous solutions in the presence of amorphous boron. The prepared samples were annealing at 700 degrees C. The structure of as-prepared samples was characterized by X-ray powder diffraction (XRD) and selected area electron diffraction (SAED) and surface area (BET) and porosity determination (BJH). The morphology and microstructure characteristics were obtained by scanning electron microscopy (SEM) and high-resolution electron microscopy (HRTEM). The method of UV/vis diffuse reflectance spectroscopy was employed to estimate band gap energies of the boron-doped titania. The photoactivity of the prepared samples was assessed by the photocatalytic decomposition of Orange II dye in an aqueous slurry during irradiation at 365 and 400 nm wavelength. The prepared titania samples doped with boron(III) oxide showed better photocatalytic activity in comparison with the reference TiO(2) sample. These photocatalysts showed better photocatalytic performance under visible-light irradiation.

Preparation of a titanium dioxide photocatalyst codoped with cerium and iodine and its performance in the degradation of oxalic acid

A novel class of visible light-activated photocatalysts was prepared by codoping TiO(2) with cerium and iodine (Ce-I-TiO(2)). The particles were characterized using the Brunauer-Emmett-Teller method, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and UV-Visible light absorption. Particles of Ce-I-TiO(2) had greater photoabsorption in the 400-800 nm wavelength range than iodine-doped TiO(2) (I-TiO(2)). The effects on the photocatalytic degradation of oxalic acid under visible light or UV-Visible light irradiation were investigated. The photocatalytic activity of Ce-I-TiO(2) calcined at 673 K was significantly higher than that of Ce-I-TiO(2) calcined at 773 K and I-TiO(2) calcined at 673 K in aqueous oxalic acid solution under visible light or UV-Visible light irradiation. Under visible light irradiation, oxalic acid was first adsorbed on the surface of the catalysts rather than reacted with free radicals in the bulk solution, and then oxidized by (·)OH(ads) to CO(2), which was verified by studying the effects of nitrogen purging and scavengers, as well as by gas chromatography/mass spectrometry.