Search

In this study, Ag2CrO4@NiFe-LDH nanoparticles were synthesized by hydrothermal method for photocatalytic degradation of Alizarin Red (AR) dye. Three composites with different molar percentages were prepared, among which 50%Ag2CrO4@50%NiFe-LDH composite was the best sample with a removal rate of 97.1% in AR degradation. Also, the properties, structure, and characteristics of pure Ag2CrO4 and NiFe-LDH and their composites were determined by XRD, FESEM, FTIR, EDX mapping, and UV–visible analyses. It was found that Ag2CrO4@NiFe-LDH composites with the formation of heterogeneous structure of Z-scheme, in addition to increasing the active sites and increasing the specific surface, decrease the recombination rate of pure Ag2CrO4 and NiFe-LDH. Also, the Box–Behnken design technique, which is one of the most common designs used in response surface methodology, was used to optimize the operating conditions and investigate the effect of 4 independent parameters: catalyst amount, solution concentration, pH, and light intensity. The importance of independent parameters and their interactions were determined by ANOVA. By means of numerical optimization, the optimal values of the selected parameters equal to 1.34 g/L of catalyst, concentration of 16.45 mg/L, pH = 10.74, and light intensity of 15.53 W were obtained as optimal conditions with a desirability coefficient of 1.00 and an absorption value of 89.34%. The closeness of adjusted R2 (0.9838) and predicted R2 (0.9507) values show that this model can be successfully used for prediction. [ABSTRACT FROM AUTHOR]

A ternary nanocomposite, BaTiO3–CNT/Ag, was synthesized via a coprecipitation method to function as a photocatalyst for pollutant degradation and H2 production through a water-splitting reaction. The successful preparation of the nanocomposite and the enhancement of its morphological properties were confirmed through Raman spectroscopy, X-ray diffraction/photoelectron spectroscopy (XRD/XPS), and scanning/transmission electron microscopy (SEM/TEM) studies. Utilizing transient photocurrent, photoluminescence (PL) spectroscopy, UV–visible diffuse reflectance spectroscopy (DRS), Mott–Schottky, and electrochemical impedance spectroscopy (EIS) tests, it was determined that the incorporation of carbon nanotube (CNT) and Ag into BaTiO3 led to a promotion of charge separation efficiency up to 15 times, a decrease in the bandgap energy from 3.12 to 2.85 eV, larger band bending, lower electron/hole recombination, and extensive lower internal resistance. In photodegradation-related studies, the response surface methodology (RSM) method was performed for experimental design to optimize the amounts of photocatalyst dosage, irradiation time, and initial dye concentration, yielding optimal values of 0.681 g/L, 67.5 min, and 1 mg/L, respectively. The sample showed outstanding photocatalytic efficiency in the degradation of different organic water pollutants, coupled with remarkable stability and reusability, as evidenced by a four-run cyclic experiment. Finally, the evaluation of H2 production revealed a remarkable amount of 542.4 μmol/g·h for the ternary nanocomposite, which is about 5 times higher than that of the pure BaTiO3 sample. This research provides thorough insight into the synthesis of a ternary nanocomposite that extremely enhances the charge transfer abilities and, therefore, boosts the photocatalytic H2 production and photodegradation of pollutants. [ABSTRACT FROM AUTHOR]

Use of the zeolite adsorbents is one of the low-cost methods in gas purification processes. The aim of this work is to synthesize three types of zeolite/quasi-zeolite through hydrothermal technique and evaluate their performance efficiency in the hydrogen gas purification. The gas mixture contained hydrogen, carbon dioxide and methane. The results indicated that at different pressures, the adsorption of the desired gases at lower temperatures is more favorable. Although all three adsorbents had great performance, for all three adsorbents, carbon dioxide adsorption was higher than methane adsorption, and the order of efficiency was as follows: NaA>SAPO-34>BaA. However, SAPO-34 owned a more superior functioning in absorbing methane, and the performance was as follows: SAPO-34>NaA>BaA. It should be remarked that at pressures less than 300 kPa, the adsorption of the desired gases in the BaA adsorbent reached a higher value faster and shows the superb acting of this adsorbent at low pressures. [ABSTRACT FROM AUTHOR]

Box-Behnken experimental design was utilized to model and optimize the photocatalytic removal of methylene blue (MB) using ZnO-BiFeO3 composite under visible light (LED). Three catalysts with different ZnO:BiFeO3 molar ratios (2:1, 1:2, and 1:1) were synthesized successfully using the hydrothermal method. The structural, morphological, and optical properties of the synthesized photocatalysts were analyzed by X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-ray Spectroscopy (EDX), Fourier Transform Infrared Spectra (FT-IR), Ultraviolet Visible Spectrometer (UV–vis), Transmission Electron Microscopy(TEM), High-Resolution Transmission Electron Microscopy (HR-TEM), and Photoluminescence (PL) Spectrophotometry. FESEM showed the relatively uniform distribution of BiFeO3 crystalline particles on ZnO ones. UV–vis analysis showed that the photocatalytic performance of pure ZnO and BiFeO3 under visible light irradiation is weak, while ZnO-BiFeO3 with a 2:1 molar ratio composite with a bandgap of about 2.37 eV showed high performance. This improved photocatalytic activity may be due to the heterogeneous synergistic effect of the p–n junction. In order to optimize the experimental conditions, four factors of initial MB concentration (5 to 20 mg/L), pH (3 to 12), catalyst dosage (0.5 to 1.25 mg/L), and light intensity (4 to 18 W) were selected as independent input variables. Box–Behnken experimental design method (BBD) suggested a quadratic polynomial equation to fit the experimental data. The results of the analysis of variance (ANOVA) confirmed the goodness of fit for the suggested model (predicted- and adjusted-R2 0.99). The optimum conditions for maximizing the photocatalytic MB degradation were found to be an initial MB concentration of 11 mg/L, pH of 11.7, catalyst dosage of 0.716 mg/L, and light intensity of 11.4 W. Under the optimum conditions, the highest photocatalytic MB degradation of 62.9% was obtained, which is in reasonable agreement with the predicted value of 69%. [ABSTRACT FROM AUTHOR]

Summary: Cadmium sulfide (CdS) is one of the most famous photocatalyst for water splitting because of relevant band edge position. But it has disadvantage such as recombination of charge carrier and photocorrosion in pure water that sacrificial materials must be used to fix it. On the other hand, the use of other photocatalysts alongside it can greatly eliminate these disadvantages. So, in favor of boosting photocatalytic efficiency, it was coupled with BiFeO3 that is a promising visible light active perovskite structure and has ferroelectric properties. The CdS and BiFeO3 powders were synthesized by precipitation and hydrothermal methods, respectively. The pure samples and heterojunctions were investigated by XRD, FESEM, transmission electron microscopy, EDX, UV‐vis, PL, N2 adsorption/desorption isotherms, photocurrent density measurement, electrochemical impedance spectroscopy and Mott‐Schottky analysis to compare the structure, composition, morphology, and optical property before and after modification. The maximum photocatalytic activity, 600.2 μmol/g/h was obtained by heterojunction containing 50 wt% BiFeO3 (CB‐50) from pure water. Also from the experiments results, CB‐50 showed much higher reusability than pure CdS. The enhanced stability and photocatalytic activity of CB‐50 are mainly attributed to charge separation as a result of Z‐scheme charge transfer mechanism as well as the increased light absorption efficiency. In addition to increasing hydrogen production, the ability to use pure water in a closed system without additional materials is other advantage of this photocatalyst. [ABSTRACT FROM AUTHOR]

Summary: The two‐layer photocatalytic membranes fabricated from a porous polyethersulfone‐TiO2 (PES‐TiO2) as a photocatalytic layer and a thin nonporous layer of poly‐ether‐block‐amide (PEBAX‐1657) as a selective layer were used to solve the problems of slurry photocatalyst systems and substitute a single operating unit for simultaneous separation and conversion of CO2. The photocatalytic features, hydrophilicity, surface chemistry, and morphology of photocatalytic membranes were characterized by Ultraviolet–visible (UV‐visible), contact angle, Attenuated Total Reflection‐Fourier Transforms Infrared (ATR‐FTIR), and (Scanning Electron Microscopy) SEM, respectively. Compared with membrane without any nanoparticle, the separation performance of nanocomposite membranes using the gas mixture (containing CO2 and CH4 with the molar ratio of 1:4), as the feed, was slightly increased by adding TiO2 content in the support layer. The effects of TiO2 nanoparticle contents, water flow rates as well as light powers on the photoreduction of CO2 to methanol in terms of methanol concentration and production yield were investigated under Ultraviolet (UV) irradiation. As depicted by UV‐vis analysis, the UV irradiation absorption of photocatalytic membranes increased with increasing of TiO2 contents. Moreover, the ATR‐FTIR results confirmed the presence of TiO2 nanoparticle on the photocatalytic membrane surface. The photocatalytic performance revealed that utilizing simultaneous separation and conversion for CO2 photoreduction in the presence of water represented the high methanol production yield about 697 μmol/gcat.h at 5 wt. % of TiO2 nanoparticle contents, 3 mL/min of water flow rate and 8.84 W/cm2 of light power. Meanwhile, the possible mechanism of the TiO2 photocatalytic performance for CO2 photoreduction to methanol was clarified. In addition, it was confirmed that the photocatalytic membranes were efficient until after four runs. Therefore, the utilization of photocatalytic membrane is an effective approach to improve the beneficial combination of photocatalytic process and membrane technology, simultaneously. [ABSTRACT FROM AUTHOR]

Summary: The use of floatable photocatalyst supports is an operable strategy of increasing photocatalytic performance in terms of improving light absorption. In this work, floatable organic support based on poly(vinyl alcohol) (PVA) was used to float commercial TiO2 P25 nanoparticles. At first, by the use of CaCl2 and boric acid at pH 3 the cross‐linking of PVA blended with sodium alginate (PVA‐Alg) was improved to enhance chemical and mechanical stability, and then it was chemically modified by trimethylchlorosilane to achieve floatable organic support (modified or MPVA‐Alg). The prepared support and photocatalyst were characterized by X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), scanning electron microscopy, energy‐dispersive X‐ray spectroscopy (EDX)‐elemental mapping, inductively coupled plasma optical emission spectroscopy, ultraviolet‐visible (UV‐vis) diffuse reflectance spectroscopy, photoluminescence (PL), thermalgravimetry, Brunauer‐Emmett‐Teller (BET), and water contact angle (WCA) analyses and applied for the ammonia degradation under UV to visible regions. Results of WCA and FTIR confirmed that chemical modification of PVA‐Alg led to lowering hydrophilicity to be floated on the ammonia wastewater. UV‐vis analysis indicated that the MPVA‐Alg acts as a light absorbent in UV‐vis ranges and makes TiO2/MPVA‐Alg a visible light active composite. Also, the PL analysis showed that the charge recombination process was strongly suppressed in the case of the TiO2/MPVA‐Alg sample. BET theory suggested that the textural properties were not the key factor in determining photocatalytic performance. The maximum photocatalytic ammonia removal was obtained to be 63% and 57% by the TiO2/MPVA‐Alg composite under UV‐vis light irradiations, respectively. The MPVA‐Alg and TiO2 exhibited the ammonia degradation of 28.5% and 15.2% under visible and 29.4% and 40.0% under UV irradiation, respectively. The TiO2/MPVA‐Alg showed favorable reuse ability after five runs due to desirable chemical and mechanical resistance. This study provides an insight into the modification of polymeric structures to be used as both floatable photocatalyst support and light sensitizer. [ABSTRACT FROM AUTHOR]

The nanoparticles of WO3 doped with Fe ions have been employed for University, Kermanshah photocatalytic conversion of greenhouse gaseous of CO2 and CH4 under visible-light irradiation. The photocatalysts have been characterized by XRD, FESEM, EDX, Raman, UV-vis, and PL techniques. The XRD and Raman spectroscopies confirm the monoclinic structure of WO3 nanoparticles and also the successful incorporation of Fe ions into WO3 lattice. A red shift in Raman patterns of Fe-doped WO3 samples indicate the partial substitution of W with Fe ions and the structural defects induced in WO3 crystals upon doping treatment. The recorded PL signals reveal that the charge carrier recombination rate can be inhibited by doping WO3 with Fe ions. The modified samples show high activity by photons with wavelength equal to/greater than ~500 nm, the visible-light in green region. The best photocatalytic reduction of CO2 is provided to be 38.7% by WO3 containing 4.18 at.% Fe under visible-light. Ethane, and formate and acetate derivatives are detected as the major products of CO2 reduction. [ABSTRACT FROM AUTHOR]