Methyl Orange Aqueous Solution Research Articles

Defective multi-element hydroxides nanosheets for rapid removal of anionic organic dyes from water and oxygen evolution reaction

Water pollution by dyes is one of the biggest environmental problems. Adsorption technology has been widely used in wastewater treatment. In this work, high-entropy concept is used to design surface defective hydroxides realizing the rapid removal of dyes from water. Multi-element hydroxides (MEHs) containing three (CoMnNi, MEH-Ternary), four (CoMnNiZn, MEH-Quaternary), and five (CoMnNiZnFe, MEH-Quinary) metal elements are successfully synthesized through a polyol process. These as-synthesized MEHs are composed of nanosheets with a brucite-like structure. Along with the increase in compositional complexity (i.e., configurational entropy), the thickness of the nanosheets in these MEHs decreases, while the degree of surface defects increase. These surface defects are probably the active sites for anionic dyes adsorption, suggesting rapid adsorption kinetics with shortened diffusion path length. For MEH-Quinary in 0.2 mM Congo red (CR) and MEH-Ternary in 0.4 mM methyl orange (MO) aqueous solutions, respectively, high removal efficiency > 99.0% is achieved in the first 30 s. Their pseudo-second-order rate constants are two orders of magnitude higher than that of activated carbon and hydrotalcite. MEH-Quinary has maximum CR and MO adsorption quantity of 546.4 and 404.9 mg g-1, respectively, by Langmuir model. The MEH-Quinary is also a potential electrocatalyst for oxygen evolution reaction.

Degradation of Methyl Orange in Aqueous Solution via Magnetic TiO2/Fe3O4 Conjugated with Persulfate

Degradation of Methyl Orange in Aqueous Solution via Magnetic TiO2/Fe3O4 Conjugated with Persulfate

Preparation of metal organic framework materials with defects via a mixed-metallic centers strategy for enhanced removal of organic dye

Metal organic framework (MOF) materials display intriguing potential in wastewater treatment applications. In this study, a series of mixed MOF materials with several defects were designed and prepared via a strategy of mixed-metallic centers and the reaction process was lasted for only several hours at room temperature with water as environmental-friendly reaction medium. The MOF materials were characterized by Brunauer-Emmett-Teller (BET), Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), and were employed to enrich organic dyes from aqueous solution with methyl orange (MO) and methylene blue (MB) as model molecules. Several factors influencing adsorption efficiency such as contact time, initial concentration, pH of dye solution and ionic strength were systematically explored. Due to the difference of structure and charge of MO and MB, the adsorption behaviors of the materials for both model dyes were obviously different from each other. The results showed that the adsorption process could be better described by pseudo-second-order kinetics and Freundlich isotherm model. The adsorption capacity of mixed MOF material with the ratio of Co2+ and Ni2+ of 1:1 for MO was 380.91 mg/g, much higher than those of MOF materials with single metallic center (255.15 mg/g of the material with Co2+ and 176.65 mg/g of the material with Ni2+), indicating the advantages of the preparation strategy and defects of the mixed MOF material produced in the preparation process in the adsorption field. However, the adsorption capacities of the prepared MOF materials for MB were close to each other. Furthermore, it would be possible to achieve a highly selective adsorption of MO from the mixed aqueous solution of MO and MB through choosing the appropriate NaCl concentration. This study can provide a method of increasing the diversity and functionality of the MOF materials.

Green Synthesis of NiO-SnO2 Nanocomposite and Effect of Calcination Temperature on Its Physicochemical Properties: Impact on the Photocatalytic Degradation of Methyl Orange

Background: Nickel stannate nanocomposites could be useful for removing organic and toxic water pollutants, such as methyl orange (MO). Aim: The synthesis of a nickel oxide-tin oxide nanocomposite (NiO-SnO2 NC) via a facile and economically viable approach using a leaf extract from Ficus elastica for the photocatalytic degradation of MO. Methods: The phase composition, crystallinity, and purity were examined by X-ray diffraction (XRD). The particles' morphology was studied using scanning electron microscopy (SEM). The elemental analysis and colored mapping were carried out via energy dispersive X-ray (EDX). The functional groups were identified by Fourier transform infrared spectroscopy (FTIR). UV-visible diffuse reflectance spectroscopy (UV-vis DRS) was used to study the optical properties such as the absorption edges and energy band gap, an important feature of semiconductors to determine photocatalytic applications. The photocatalytic activity of the NiO-SnO2 NC was evaluated by monitoring the degradation of MO in aqueous solution under irradiation with full light spectrum. The effects of calcination temperature, pH, initial MO concentration, and catalyst dose were all assessed to understand and optimize the physicochemical and photocatalytic properties of NiO-SnO2 NC. Results: NiO-SnO2 NC was successfully synthesized via a biological route using F. elastica leaf extract. XRD showed rhombohedral NiO and tetragonal SnO2 nanostructures and the amorphous nature of NiO-SnO2 NC. Its degree of crystallinity, crystallite size, and stability increased with increased calcination temperature. SEM depicted significant morphological changes with elevating calcination temperatures, which are attributed to the phase conversion from amorphous to crystalline. The elemental analysis and colored mapping show the formation of highly pure NiO-SnO2 NC. FTIR revealed a decrease in OH, and the ratio of oxygen vacancies at the surface of the NC can be explained by a loss of its hydrophilicity at increased temperatures. All the NC samples displayed significant absorption in the visible region, and a blue shift is seen and the energy band gap decreases when increasing the calcination temperatures due to the dehydration and formation of compacted large particles. NiO-SnO2 NC degrades MO, and the photocatalytic performance decreased with increasing calcination temperature due to an increase in the crystallite size of the NC. The optimal conditions for the efficient NC-mediated photocatalysis of MO are 100 °C, 20 mg catalyst, 50 ppm MO, and pH 6. Conclusions: The auspicious performance of the NiO-SnO2 NCs may open a new avenue for the development of semiconducting p-n heterojunction catalysts as promising structures for removing undesirable organic pollutants from the environment.

In situ synthesis and immobilization of CuO nanoparticles in alginate-poly(amido amine) nanogels for photocatalytic applications

Herein, we report a feasible approach for preparation of crosslinked alginate (Alg) and poly(amido amine) (PAMAM) nanogels (Alg-PAMAM NGs), using a water-in-oil-in-water (w/o/w) double emulsion route, via strong electrostatic interactions between anionic groups coming from alginate and previously incorporated Cu2+ ions. CuO nanoparticles (NPs) with average diameter about 65 nm were in situ obtained into Alg/PAMAM nanogels by treatment of embedded Cu2+ ions in NGs with NaBH4 at 25 °C under air atmosphere. The prepared Alg-PAMAM and Alg-PAMAM-CuO NGs were characterized using FT-IR and UV–visible spectroscopy, as well as scanning transmission electron microscopy (STEM). The presence of PAMAM dendrimers helped both to obtain structurally compact nanogels and an adequate stabilization of CuO NPs. Finally, the photocatalytic performance of the Alg-PAMAM-CuO NGs was tested via the decomposition of methyl orange in aqueous solution, under visible light irradiation.

Structure and optical, magnetic and photocatalytic properties of Cr3+ substituted zinc nano-ferrites

In this paper, the Cr3+ substituted zinc ferrite (ZnCrxFe2-xO4 with x = 0, 0.15 and 0.25) nanoparticles with single cubic spinel structure (Fd-3 m space group) were prepared by chemical co-precipitation method, and their structure and optical, magnetic and photocatalytic performaces were investigated. With Cr added, the lattice parameter and average grain size of the ferrites remarkably changed. High-quality nanostructured ferrite with an average particle size of 22–31 nm are revealed by TEM and SEM. The vibrational stretching modes of tetrahedral and octahedral sites were confirmed by FTIR. The optical studies proved a gradual decrease in the optical band gap which indicated the emergence of sub-band-gap energy levels by the chromium content. The magnetic properties were investigated through magnetization technique. The saturation magnetization measured from M-H hysteresis plot show decreasing trend with increase in Cr3+ content. The photocatalytic degradation of aqueous solution of Methyl Orange (MO) in the presence of prepared nano-ferrite under visible-light irradiation has been studied and discussed. The photodegradation efficiency of MO over ZnCrxFe2-xO4 photocatalysts is enhanced; (69%, 74% and 82% with increasing Cr3+content, respectively) compared with its modest value 12% without addition.

Investigation of Interaction Mechanisms of High Energy Electrons and Gamma Quantum with Aqueous Solution of Methyl Orange Dye

The level of development of modern nuclear technologies forms a request for the development of new branches of science. At the same time, chemical dosimetry methods are also being improved [1, 2]. The essence of such methods consists in the quantitative determination of the radiation-chemical damages to the molecules of a substance when it is exposed to ionizing radiation [3, 4]. Liquid and solid solutions of organic dyes have intense bands optical absorption and fluorescence in the visible region of the spectrum, which makes it possible to use them in dosimetry systems [5, 6]. The use of organic dyes makes it possible to determine the absorbed dose in the range from 10-6 to 104 M Rad [7, 8]. In this work, we studied the processes of interaction of gamma-ray and high-energy electron fluxes with an aqueous solution of the organic dye methyl orange (C14H14N3О3SNa) [9, 10]. The calculations and experiment were carried out on a resonant electron accelerator with energies up to 30 MeV. The electron beam energy was 15 MeV. A tungsten converter was used to generate gamma quanta. The thickness of the converter varied from 0 to 6 mm. We have developed a computer program in C++ to simulate the irradiation process. This program uses the Geant4 class library based on the Monte Carlo method and runs in multi-threaded mode. For calculations, the model “PhysicsList emstandard_opt3” was chosen as the most suitable one. The value of radiation damage per one incident electron and produced gamma-quantum is determined in the work. The simulation results are compared with experimental data. Based on the results obtained, conclusions were drawn about the main mechanisms leading to the decomposition of organic dye molecules, and methods for optimizing the experiment for further research were proposed.

Activation of sulfite by metal-organic framework-derived cobalt nanoparticles for organic pollutants removal

Sulfite (SO32−) activation is one of the most potential sulfate-radical-based advanced oxidation processes, and the catalysts with high efficiency and low-cost are greatly desired. In this study, the cobalt nanoparticles embedded in nitrogen-doped graphite layers (Co@NC), were used to activate SO32− for removal of Methyl Orange in aqueous solution. The Co@NC catalysts were synthesized via pyrolysis of Co2+-based metal-organic framework (Co-MOF), where CoO was firstly formed at 400℃ and then partially reduced to Co nanoparticles embedded in carbon layers at 800℃. The Co@NC catalysts were more active than other cobalt-based catalysts such as Co2+, Co3O4 and CoFe2O4, due to the synergistic effect of metallic Co and CoxOy. A series of chain reaction between Co species and dissolved oxygen was established, with the production and transformation of SO3•−, SO52−, and subsequent active radicals SO4•− and HO•. In addition, HCO3− was found to play a key role in the reaction by complexing with Co species on the surface of the catalysts. The results provide a new promising strategy by using the Co@NC catalyst for SO32− oxidation to promote organic pollutants degradation.

Fast and effective catalytic degradation of an organic dye by eco-friendly capped ZnS and Mn-doped ZnS nanocrystals.

Undoped and manganese doped ZnS nanocrystals encapsulated with thioglycolic acid(ZnS-TGA) were synthesized and characterized with different techniques, and finally tested in the photodegradation of a methyl orange in aqueous solution under UV and sunlight irradiations. FTIR and X-ray diffraction results confirmed the functionalization of these nanocrystal surface by thioglycolic acid and the formation of crystalline structures of ZnS and Mn-doped ZnS with cubic and hexagonal phases. Calculated average size of ZnS nanocrystals was in the range of 2-3nm. It was observed a blue shift of the absorbance threshold and the estimated bandgap energies were higher than that of Bulk ZnS thus confirming the quantum confinement effect of charge carriers. Photoluminescence spectra of ZnS nanocrystals exhibited emission in the range of 410-490nm and the appearance of an additional emission band around 580nm (2.13eV) connected to the 4T1 → 6A1 transition of the Mn2+ions. Photodegradation of methylene orange with undoped and Mn-doped ZnS-TGA nanocrystals was investigated. Dye adsorption prior to photocatalysis using nanocrystals was studied via kinetic and equilibrium experiments. The maximum dye adsorption capacity on doped ZnS-TGA was ~ 26.98mg/g. The adsorption kinetic was found to follow the pseudo-second-order kinetic model. A statistical physics model was used to analyze the equilibrium data where the calculated adsorption energy was 17-18kJ/mol. It was concluded that the dye adsorption was associated to the hydrogen interaction where the removal process was feasible and multi-molecular at 25°C. The photocatalytic activity of undoped ZnS nanoparticles under UV irradiation showed better efficiency than doped nanocrystals thus indicating that manganese doping generated a dropping of the photocatalytic degradation of the dye. Dye degradation efficiency of 81.37% using ZnS-TGA nanocrystals was achieved after 6min, which indicated that ZnMnS-TGA nanocrystals may be considered an alternative low cost and environmental friendly material for facing water pollution caused by organic compounds via photodegradation processes.

Contact-electro-catalysis for the degradation of organic pollutants using pristine dielectric powders

Mechanochemistry has been studied for some time, but research on the reactivity of charges exchanged by contact-electrification (CE) during mechanical stimulation remains scarce. Here, we demonstrate that electrons transferred during the CE between pristine dielectric powders and water can be utilized to directly catalyze reactions without the use of conventional catalysts. Specifically, frequent CE at Fluorinated Ethylene Propylene (FEP) - water interface induces electron-exchanges, thus forming reactive oxygen species for the degradation of an aqueous methyl orange solution. Contact-electro-catalysis, by conjunction of CE, mechanochemistry and catalysis, has been proposed as a general mechanism, which has been demonstrated to be effective for various dielectric materials, such as Teflon, Nylon-6,6 and rubber. This original catalytic principle not only expands the range of catalytic materials, but also enables us to envisage catalytic processes through mechano-induced contact-electrification.

Sorption-photocatalytic performance of NbOx nanocrystals synthesized via heat-stimulated oxidation of niobium carbide

In this work, nano-sized niobium oxides with different crystal structures can be produced by thermal treatment of nonstoichiometric nanocrystalline niobium carbide (NbCy) and serve as effective sorbents and photocatalytic materials. Differential thermal analysis of initial NbCy powder was carried out, and temperatures of thermal treatment for the were chosen. The nanopowders were studied using powder X-ray diffraction, scanning electron microscopy, low-temperature N2 adsorption–desorption, X-ray photoelectron spectroscopy and diffuse reflectance electron spectroscopy methods. The specific surface area of samples annealed at 100, 200, 300, 400, 500 °C was about 224, 255, 273, 224 and 47 m2/g, respectively. The photocatalytic activity of the obtained nanopowders was analyzed during the oxidation of an aqueous solution of methyl orange on exposure to visible light. The photocatalytic activity of nanopowders grows with the annealing temperature increasing from 100 to 500 °C and reaches the maximum value for the higher niobium oxide Nb2O5. The time of complete decoloration of dye was 165 min. The tests performed to establish the sorption equilibrium between catalyst and dye in the dark revealed that the nanopowder produced during annealing at 300 °C possesses a high sorption capacity of 76.5%, which allows it to be considered as an effective sorbent.

Production and Optimization of Bio-Based Silica Nanoparticle from Teff Straw (Eragrostis tef) Using RSM-Based Modeling, Characterization Aspects, and Adsorption Efficacy of Methyl Orange Dye

The brown teff straw was utilized in this study to produce silica using the sol-gel technique. After pretreatment, the raw material of brown teff straw was characterized. The data were analyzed using the central composite design and response surface technique, and four independent parameters, namely, temperature, NaOH concentration, rotational speed, and extraction time, were evaluated for process optimization. Before extracting silica with an alkaline solution, the silica content in the ash was determined using an AAS spectrometer. The silica content of teff straw ash is around 92.89%. The ash was treated with NaOH solution in the concentrations range of 1 M to 3 M (0.5 M interval). The extraction time varied at intervals of 55, 70, 85, 100, and 115 minutes. Temperatures were changed using magnetic stirrer equipment in the range of 80°C to 100°C (5°C interval). At 350 rpm, 400 rpm, 450 rpm, 500 rpm, and 550 rpm, the rotating speed was adjusted. The best extraction conditions for amorphous silica were 1.50 M NaOH, 109.99 min, 94.98°C, and a rotating speed of 499.57 rpm, with a maximum yield of 85.85%. XRD and FTIR analyses were used to assess the physicochemical characteristics of the extracted silica. The aqueous solutions of methyl orange were used to test the adsorption efficiency of silica. The percent of removal efficiency for methyl orange was 90.48%.

Studies on Synthesis and Characterization of Fe3O4@SiO2@Ru Hybrid Magnetic Composites for Reusable Photocatalytic Application

Degradation of dye pollutants by the photocatalytic process has been regarded as the most efficient green method for removal organic dyes from contaminated water. The current research work describes the synthesis of Fe3O4@SiO2@Ru hybrid magnetic composites (HMCs) and their photocatalytic degradation of two azo dye pollutants, methyl orange (MO) and methyl red (MR), under irradiation of visible light. The synthesis of Fe3O4@SiO2@Ru HMCs involves three stages, including synthesis of Fe3O4 magnetic microspheres (MMSs), followed by silica (SiO2) coating to get Fe3O4@SiO2 MMSs, and then incorporation of presynthesized Ru nanoparticles (~3 nm) onto the surface of Fe3O4@SiO2 HMCs. The synthesized HMCs were characterized by XRD, FTIR, TEM, EDS, XPS, BET analysis, UV-DRS, PL spectroscopy, and VSM to study the physical and chemical properties. Furthermore, the narrow band gap energy of the HMC photocatalyst is a significant parameter that provides high photocatalytic properties due to the high light adsorption. The photocatalytic activity of synthesized Fe3O4@SiO2@Ru HMCs was assessed by researching their ability to degrade the aqueous solution of MO and MR dyes under visible radiation, and the influence of various functional parameters on photocatalytic degradation has also been studied. The results indicate that the photocatalytic degradation of MO and MR dyes is more than 90%, and acid media favors better degradation. The probable mechanism of photodegradation of azo dyes by Fe3O4@SiO2@Ru HMC catalysts has been proposed. Furthermore, due to the strong ferromagnetic Fe3O4 core, HMCs were easily separated from the solution after the photocatalytic degradation process for reuse. Also, the photocatalytic activity after six cycles of use is greater than 90%, suggesting the stability of the synthesized Fe3O4@SiO2@Ru HMCs.

Comparative study on photooxidation of methyl orange using various UV/oxidant systems

Abstract In the present work, a comparative study of the photooxidation of an aqueous solution of Methyl Orange (MeO) has been realized using H2O2 and IO3 −, BrO3 −, ClO3 −, ClO4 −, BO3 − ions in the presence of UV low pressure mercury lamp (UV-C light at λ max = 254 nm). The initial concentration of MeO in all experiments was 6 × 10−5 mol L−1. The degradation rate of MeO follows pseudo-first-order kinetics in all UV/Oxidant systems. The highest degradation rate of MeO was in the BrO3 −/UV254nm system. Different systems were compared for an oxidant concentration of 10−2 mol L−1 and the obtained results showed that decolorization followed the decreasing order: BrO 3 − /UV 254 nm > IO 3 − /UV 254 nm > H 2 O 2 /UV 254 nm > BO 3 − /UV 254 nm > ClO 3 − /UV 254 nm = ClO 4 − /UV 254 nm = UV 254 nm . The optimization of oxidants concentration for each process was determined (10−2 mol L−1 for IO3 − which gives almost the same k app for 5 × 10−3, 10−2 mol L−1 for BO3 − and 5 × 10−2 mol L−1 for H2O2). No degradation of MeO in presence of ClO3 − and ClO4 − because these ions do not absorb at 254 nm, therefore they do not generate radical species which degrade organic pollutants. The mineralization was also studied where it was reached 97% after 5 h of irradiation for both H2O2/UV254 nm and BO3 −/UV254 nm systems.

A new type of porous Zn (II) metal-organic gel designed for effective adsorption to methyl orange dye

Metal-organic gels, which have attracted much attention and research due to their novel properties, were usually prepared with organic solution. In this paper, a new metal-organic gel was assembled by mixing proper amount of xanthine and zinc acetate in pure water with the assistance of triethylamine. The results of FTIR and XRD indicated that the hydrogel was self-assembled through coordination, hydrogen bond and π-π stacking. The hydrogel exhibited thixotropic property and good resistance to acid, alkali and heat. The xerogel obtained by freeze-drying had a porous structure with pore size ranging from several nanometers to several hundred nanometers as shown in the SEM images. The xerogel had the effectively adsorption properties for methyl orange in aqueous solution, and the adsorption efficiency is up to 80.63%. The model of adsorption kinetics and adsorptions isotherm show that the adsorption data were consistent with the Freundlich equation and the pseudo-second-order model, which mainly attribute to the chemisorption of methyl orange on multilayer heterogeneous surface of the xerogel. Prepared by a simple and mild method, the xerogel is a promising adsorbent for dye wastewater treatment.

Experimental and Density Functional Theory Studies on a Zinc(II) Coordination Polymer Constructed with 1,3,5-Benzenetricarboxylic Acid and the Derived Nanocomposites from Activated Carbon.

A coordination polymer with the composition C12H20O16Zn2 (ZnBTC) (BTC = benzene-1,3,5-tricarboxylate) was synthesized under hydrothermal conditions at 120 °C, and its crystal structure was determined using single-crystal X-ray crystallography. First-principles electronic structure investigation of the compound was carried out using the density functional theory computational approach. The highest occupied molecular orbital, the lowest unoccupied molecular orbital, the energy gap, and the global reactivity descriptors of ZnBTC were investigated in both the gas phase and the solvent phase using the implicit solvation model, while the donor–acceptor interactions were studied using natural bond orbital analyses. The results revealed that ZnBTC is more stable but less reactive in solvent medium. The larger stabilization energy E(2) indicates a greater interaction of ZnBTC in the solvent than in the gas phase. Orange peel activated carbon and banana peel activated carbon chemically treated with ZnCl2 and/or KOH were used to modify the synthesis of ZnBTC to obtain nanocomposites. ZnBTC and the nanocomposites were characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis, and Fourier transform infrared. The specific surface area (SBET) and the average pore diameter of the materials were determined by nitrogen sorption measurements using the Brunauer–Emmett–Teller (BET) method, while scanning electron microscopy and transmission electron microscopy were used to observe their morphology and particle size, respectively. The PXRD of all the activated carbon materials exhibited peaks at 2θ values of 12.7 and 13.9° corresponding to a d-spacing of 6.94 and 6.32 Å, respectively. The N2 adsorption–desorption isotherm of the materials are of type II with nanocomposites showing enhanced SBET compared to the pristine ZnBTC. The results also revealed that activated carbons from the banana peel and the derived nanocomposites exhibited better porous structure parameters than those obtained from orange peel. The degradation efficiency of methyl orange in aqueous solutions using ZnBTC as a photocatalyst was found to be 52 %, while that of the nanocomposites were enhanced up to 79 %.

Adsorption of an anionic dye from aqueous solution on a treated clay

The presence of synthetic dyes in water causes serious environmental issues due to the poor water quality, toxicity to the environment and human carcinogenic effects. Adsorption has progressively become an economical and feasible method for dye wastewater decontamination. Clay minerals are an interesting alternative for removing colorants from colored aqueous solutions because they are inexpensive, easy to extract and handle, and non-toxic. In this work, a bentonite treated with H2SO4 is used to adsorb an azoderivative dye such as methyl orange (MO). The physicochemical properties of the solids were evaluated through X-ray powder diffraction (XRD), Brunauer Emmett Teller surface area analysis (BET), Scanning electron microscopy coupled with Energy dispersive spectroscopy (SEM-EDS), and Fourier transform infrared spectroscopy (FTIR). The initial dye concentration, adsorbent mass, contact time, temperature and pH influence the adsorption capacity. Acid modification of the clay increased its capacity to adsorb MO. For a concentration of 200 mg/L MO, an adsorption capacity of 125 mg/g was achieved. The adsorption process follows the pseudo second-order kinetic model. The thermodynamic study indicates that the adsorption is spontaneous and exothermic. The adsorption isotherm is best fitted to the Freundlich mathematical model. The results obtained show that, after receiving an acid treatment, clay can be effectively used to remove MO in aqueous solution.

Effect of crystalline orientation on photocatalytic performance for Nb-doped TiO2 nanoparticles

Crystalline-oriented thick films have been fabricated with using plasma-synthesized (0–20.0 at.%) Nb-doped TiO2 powder by slip casting method in a strong magnetic field (12 T). Degree of c-axis orientation of the fabricated thick film was evaluated by Lotgering factor (f). The orientation degree along c-axis was improved by sintering at 600 °C, but was deteriorated at 700 °C. Photocatalytic performance under the UV light irradiation was conducted on the film surface and was determined by bleaching methyl orange aqueous solution. The improvement in the photocatalytic performance was greatly attributed to the dominated crystalline-orientation of the (001) plane for the Nb-doped TiO2.

Sustainable synthesis of multiple-metal-doped Fe2O3 nanoparticles with enhanced photocatalytic performance from Fe-bearing dust

An Fe-abundant solid waste, fabric filter dust (FFD) was used as the starting material for the preparation of metal-doped Fe2O3 (M−Fe2O3) nanoparticles for the photocatalytic degradation of MO aqueous solution. Valuable elements including Fe, Ti, Al, Na, Si, Ca, and Mg were extracted from the dust by hydrochloric acid leaching, transformed into sediments by increasing the pH of the lixivium orderly, and converted into M−Fe2O3 nanoparticles by the sol–gel technology. The effects of pH for the precipitation process and firing temperature for the sol–gel method were investigated systematically. The M−Fe2O3 samples were characterised using X-ray diffraction, field emission scanning electron microscopy, Brunauer–Emmett–Teller analysis, UV–vis spectra, and energy dispersive spectroscopy. The performances of the dust-derived nanoparticles during photocatalytic process were appraised by visible light photodegradation of methyl orange (MO) aqueous solution, indicating that the M−Fe2O3 (M = Ti and Al) sample prepared with a precipitation pH of 4 and a firing temperature of 500 °C exhibits the most impressive photocatalytic behaviour. The product produces a degradation rate of 82.99% for 100 mL of MO solution (10 mg/L) after visible-light degradation for 180 min, which is increased from 38.94% achieved by an undoped Fe2O3 sample prepared under the same conditions.

PVDF-TiO2 core-shell fibrous membranes by microwave-hydrothermal method: Preparation, characterization, and photocatalytic activity

A polyvinylidene fluoride (PVDF) - titanium dioxide (TiO2) core-shell composite nanofibrous membrane (CNM) with photocatalytic activity was obtained from the microwave-assisted hydrothermal treatment of an electrospun PVDF membrane. The effects of the precursor solution acidity, the heating temperature, and the treatment time on the structure and the photocatalytic performance were investigated. The CNM obtained from a 2 M precursor acidic solution showed the presence of nanofibers (NFs) with a proper core-shell structure, wherein a TiO2 smooth shell was uniformly covering the electrospun PVDF NFs core. The TiO2 crystallographic phase was found to be temperature-dependent, with the highest anatase content observed at 120 °C. The mean PVDF-TiO2 NFs diameter measured from SEM images and the TiO2 fraction of CNM calculated from TGA results showed an accumulation of TiO2 on the PVDF NFs surface as heating temperature and treatment time increased. The photo-oxidation capability of the as-prepared CNMs was evaluated by the photocatalytic decomposition of aqueous methyl orange solution at room temperature under UV-C irradiation. PVDF-TiO2 CNM exhibited a stable performance after five cycles of the MO degradation due to a strong connection between the TiO2 layer and the PVDF substrate. The implemented approach has been demonstrated to be a feasible method for the synthesis of core-shell PVDF-TiO2 fibrous membrane. The influence of hydrothermal process parameters on the structure and final properties of PVDF-TiO2 CNM was revealed through a detailed mechanism investigation.