جستجوی مقالات مرتبط با کلیدواژه « photodegradation » در نشریات گروه « شیمی »

A facile chemical mixing approach was used to prepare TiO2/ZnO photocatalystswith different mass ratios. The photodegradation activity was tested against paracetamol in an aqueous phase assisted by low UVC-light intensity (9 W). TiO2/ZnO particles mainly exhibited irregular shapes with uniform distributions and high crystallinity degree, the primary oxidation state in the structure is titanium Ti4+ of anatase TiO2 (459.2 and 464.9 eV), and the presence of standard chemical state of Zn2+ (1021.9 and 1044.9 eV). The composite with a 1:5 mass ratio displayed a rapid and outstanding degradation percentage of 95% and a rate of 1.83 × 10-2 min-1. The best photocatalyst can be recycled up to five times towards paracetamol degradation without any regeneration step or severe deactivation. A Fuzzy inference system (FIS) was computed for the first time to investigate the relationship between the TiO2/ZnO ratio, degradation percentage, and rate constant. The optimal concentration of 9 mg/L was obtained, whereby the degradation percentage and rate were sufficiently maintained above 90% and 0.19 mg/L.min, respectively. Using a fuzzy logic controller (FLC) in this work enables future guidance and prediction for developing the best TiO2/ZnO photocatalysts for real-world water remediation processes.Highlights 1.      Facile preparation of TiO2/ZnO composite photocatalyst via simple mixing for degradation of paracetamol under low UVC light intensity (9 W).  2.      TiO2/ZnO particles are mostly exhibited irregular shapes with uniform distributions and high crystallinity degree, the main oxidation state in the structure is titanium Ti4+ of anatase TiO2 (459.2 and 464.9 eV), and the presence of standard chemical state of Zn2+ (1021.9 and 1044.9 eV).  3.      TiO2/ZnO (1:5) displayed a rapid and outstanding degradation percentage of 95% and rate of 1.83 × 10-2 min-1, in accordance with pseudo first-order kinetics. 4.      The optimal concentration of 9 mg/L was computed by the prediction using fuzzy inference system (FIS) for the first time, whereby the degradation percentage and rate were sufficiently maintained above 90% and 0.19 mg/L.min, respectively. 5.      The stability of TiO2/ZnO composite photocatalyst towards paracetamol degradation was retained up to 5 cycles, without undergo any regeneration procedure.

In this study, Sr Gdx Fe(12 –x) O19 nanostructures (x= 0, 0.2(3% Gd), 0.4 (6%Gd),0.6(9%Gd), 0.8 (12%Gd)) were synthesized by self-combustion sol-gel method and then calcined at the temperature of for 3 h. This compound was then composited with functionalized graphene oxide (GO) for the photocatalytic degradation of Enrofeloxacin. FESEM, EDS, XRD, and FTIR analysis were employed to investigate the particle size, elemental composition, morphological structure, functional groups determination and structural composition of the samples. VSM, BET-BJH, TGA-DTA, DRS and zeta potential analysis were also used to assess the magnetic properties, surface area, thermal stability, band-gap determination and suspension stability of the specimens, respectively. For evaluation of performance, photocatalytic degradation of Enrofeloxacin (an antibiotic that is widely used for domestic animals) is performed. The results showed that the 3% and 6% Gd-doped composites had the highest efficiencies in the photocatalytic reaction.This research reports the successful synthesis of SrGdxFe12-xO19/GO-COOH composites and its characterization by various techniques. The results indicated that SrGdxFe12-xO19/GO-COOH composite can be employed as an applicable candidate for the photodegradation of ENR antibiotic drug from pharmaceutical industry effluent as well as the water resources. Analysis of the results by statistical software based on the response surface method showed that the prolongation of the radiation time and catalyst mass, as well as pH reduction, can enhance the efficiency of ENR photodegradation. By increasing the pollutant concentration, however, the degradation efficiency declined.

In this investigation, a novel type of zinc oxide supported on clinoptilolite zeolite ZnO /Clinoptilolite (ZnO/CP) nanophotocatalyst was prepared based on the solid-state dispersion (SSD) method. The prepared nanophotocatalyst was characterized with XRD and SEM techniques. As an application, the photocatalytic degradation of malachite green dye in water under UV irradiation was studied. The results show that the ZnO /CP is an active photocatalyst and the maximum effect of photodegradation was observed at 10 wt.% ZnO, 90 wt% Clinoptilolite. A first-order reaction with K = 0.0075 min-1 was concluded. The effects of some parameters such as pH, amount of photocatalyst, and temperature were also examined. Finally, a mechanism was introduced for MG photodegradation.

The sol-gel technique is employed for the synthesis of tungsten trioxide (WO3) nanosheets. The Au/WO3 nanocomposite is prepared using laser ablation employing an Nd-YAG laser operating at a wavelength of 1064 nm and utilizing gold metal. The SEM images demonstrate that WO3 was formed as nanosheets with a thickness between 36nm and 80nm.  X-ray diffraction (XRD) patterns confirmed the monoclinic crystal structure and high crystallinity of the WO3 structure. The optical absorption of both WO3 nanosheets and Au/WO3 nanocomposite exhibited a pronounced absorption edge, with an energy gap of 2.52 eV and 2.41 eV, respectively. The photocatalytic activity of WO3 nanosheets and Au/WO3 nanocomposite was determined by degrading Methylene blue (MB) dye under visible light irradiation using different catalyst doses and pH values. The WO3 nanosheets and Au/WO3 nanocomposites that were prepared demonstrate a fast degradation of MB dye. The highest photodegradation efficiency (PDE) of MB dye was 75.9% when 0.05 g of Au/WO3 nanocomposite was exposed to 7 pH for 6 min of irradiation. Nevertheless, an increase of pH led to a corresponding rise in PDE. Particularly, the PDE values reached 85.5% and 95.7% when using 0.1 g of WO3 nanosheets and Au/WO3 nanocomposite, respectively, under the conditions in a pH level of 12 and an irradiation duration of 6 minutes.

This paper deals with the comparison of the Cr (III) dopant from tannery wastewater to the Cr (III) from the pure salt solution on the character and activity of TiO2. The doping was conducted by hydrothermal method, and the Cr-doped TiO2 prepared was characterized by UV specular reflectance (SRUV), X-ray diffraction (XRD), and X-ray fluorescence instruments. The effect of the Cr (III) doping on the activity of the TiO2 was evaluated by Congo red photodegradation. The research results reveal that Cr (III) doping on TiO2 has been successfully reducing remarkably the band gap energy (Eg) from 3.13 eV to 2.64 eV, shifting into the visible region, and further noticeably improving TiO2 activity. The effect of the Cr (III) doping from the wastewater is found to be slightly higher than that of the salt solution. The highest degradation of 10 mg/L Congo red in 50 mL solution, can be reached by applying 30 mg of the photocatalyst in 60 mins and at pH 7.

Photocatalyst for the degradation of the organic dye molecules has been investigated for the highly uniform vertically aligned ZnO nanorods grown on silicon substrates by radio frequency magnetron sputtering. An intense green luminescence located at 2.192 eV is corroborated by the singly charged oxygen vacancies and it is responsible for the visible-light-driven photocatalytic response in ZnO nanorods. The higher photocatalytic activity of organic dyes under the irradiation of visible light is enhanced due to the light absorption and better charge separation (e-</sup>-h+</sup>) in vertically aligned ZnO nanorods. Further, the dye excitation is also accountable for the degradation mechanism besides surface defects under solar irradiation. Moreover, the ZnO nanorods exhibit suppressed photo corrosion and high photo-stability as evidenced by the recovery and recycling studies.

Organic dyes are among the main sources of water pollution that cause serious health problems for living organisms. Removing dye pollution from water sources is important because of its high toxicity, so it has attracted the interest of researchers. Heterogeneous photocatalysis based on ZnO is one of the most important methods of pollution treatment. The purpose of this review is to summarize the use of ZnO nanostructure and ZnO modified as photocatalysts. The studied mechanism of dye photocatalytic activity and the most important factors affecting the photocatalytic process are discussed. The major effective parameters associated with the surface and morphology to look upon for the efficient photodegradation of organic pollution are structural and average particle size, surface area, band gap crystalline structure, surface density, and porosity. The photodegradation reactions depend on the state of ionization as well as on the surface charge of the photocatalyst and organic dye because pH will determine the charge of the catalyst according to the medium. On the other hand, the calcination temperature was increased throughout the work to break down the pores, which reduces the surface area of the synthesis photocatalyst. The type of dye has an important influence on the success of the photocatalytic process.

The textile industry produces a significant amount of liquid effluent pollutants due to the vast amounts of water used in fabric processing. This has resulted in significant water pollution worldwide. The reduction of these dye compounds from industrial wastewater has been achieved using chemical, physical, and biological methods. However, these approaches are time-consuming, costly, and pose disposal problems. Currently, photocatalytic degradation by nanoparticles is attracting significant attention.  In this regard, Activated carbon supported and unsupported SrO nanoparticles were synthesized by the wet chemical co-precipitation method. The nanoparticles were characterized by XRD, SEM, EDX, and FT-IR. The Strontium oxide (SrO) and Activated carbon-supported Strontium oxide (Ac/SrO) nanoparticles (NPs) were used as photocatalysts for the photodegradation of Congo red dye in an aqueous medium under UV irradiation. The unsupported SrO and AC/SrO NPs degraded about 93.3% and 97.6% of the dye, respectively, within 100 minutes of irradiation time. The maximum degradation of the dye was achieved at pH 4, 0.06 g of catalyst dose, 15 ppm dye concentration, and a temperature of 45℃. The data were best fitted with pseudo-first-order kinetics. The activity of the recovered catalyst was also examined.

In this investigation, a fluidized bed photocatalytic reaction system was designed to eliminate emerging contaminants: acetaminophen and pyridine in water. Titanium dioxide (TiO2) doped with aluminum (Al3+) using the photo-deposition technique was used as a catalyst and supported on alumina beads (Al2O3). The catalyst´s doping was carried out by photo deposition with aluminum particles. The reactor, which is a quartz vessel with a capacity of 500 mL, where aluminum pearl, was previously impregnated with titanium oxide and calcined at 550 °C. The reactor feeding was carried out using a pump at a flow of 0.5 L/min; two lamps of UV light with 365 nm were used. The synthesized catalyst was characterized through Energy-dispersive X-ray analysis (EDX), Transmission Electron Microscopy (TEM), and X-ray diffraction (XRD) techniques, showing adequate impregnation of aluminum in the formed compound. Photoactivity analysis of the catalyst was performed at different contaminant concentrations, from 5-40 ppm for acetaminophen and 5-60 ppm for pyridine. Mineralization of more than 85% acetaminophen and 70 % pyridine was achieved after 300 min of UV illumination. The results demonstrate that using this photocatalytic arrangement as a decontamination technique for the pollutants such as acetaminophen and pyridine is feasible.

In this study, we discuss the wet chemical synthesis and experimental analysis of zinc doped Gd2O3(Gd2-xZnxO3-δ) nanoparticles where, x=0, 0.1, 0.2, 0.3, 0.4, and 0.5. The cubic crystalline structure is derived from XRD results and the existence of metal-oxide bond has been confirmed from FTIR studies. According to SEM and PSA analysis, the produced nanoparticles are found to be of nano size. The EDX data verified the presence of Gd, Zn, and O in the samples. Based on UV-visible spectroscopy, the band gap and λmax values were computed. In an aqueous medium and under UV light irradiation, the photodegradation of Rhodamine B over Zn doped Gd2O3 nanoparticles was studied. It was observed that Gd1.50Zn0.50O3-δ has exhibited 82% of photo-degradation of the dye solution which further increased to 96% because of increasing the catalyst loading. The effect of pH and the concentration of the dye are also reported. According to the kinetic analysis, the photocatalysis process followed a pseudo-first-order kinetic model. A radical scavenger technique was used to further examine and identify the function of photoactive species.

Graphene assisted photodegradation have been used extensively as a remedial measure against pollutant dyes over last few years. The present work highlighted the comparative photodegradation effects between functionalized graphene oxide (GO) and non-functionalized graphene (Gr) maintained at room temperature (~27o C) against three different pollutant dyes viz. malachite green (MG), methylene blue (MB) and methyl orange (MO) under visible light exposure at neutral medium (pH ~ 7). The degradation of MG and MB were remarkably high upon using the functionalized GO while non-functionalized Gr had comparatively less degradation efficiency against both these dyes. On the other hand, Gr was found to be effective than GO in combatting the azoic MO dye due to poor recombination of carrier charges. The photodegradation of 1:1:1 mixture of MG:MB:MO (dye cocktail) was studied in presence of GO, separated in HPLC to estimate the degradation efficiency of each dye. The mineralized products obtained from the LC-MS/MS suggested the fragmentations in each dye occurred via demethylation route followed by asymmetric cleaving.  In real-time, the growth assessment of Lemna Minor and Eichhornia crassipes was monitored in dye cocktail alone and in presence of GO treated dye cocktail.

Eight eco-friendly, and magnetically-separable heterogeneous photocatalysts including five Au nanoparticles (NPs) modified magnetic TiO2@Fe3O4 NPs and three Ag-Au bi-plasmonic NPs-decorated TiO2@Fe3O4 NPs with enhanced photocatalytic performance under visible light were synthesized and used for photodegradation of methyl orange (MO) as a model pollutant in textile wastewater samples. The photocatalytic activity was assessed using two radiation sources namely, an intense linear 532-nm laser and a continuous solar-simulated xenon lamp. Compared to the TiO2 alone, the prepared photocatalysts revealed efficient photocatalytic activity in visible region due to the presence of two localized surface plasmon resonance (LSPR)-generated hot electrons from excited Au and Ag NPs and reached to about 98% in 60 min. In addition, the results demonstrated that the photocatalysts have different degradation performance with respect to the type of applied light sources and also to the composition/shell thickness of plasmonic layer. The Langmuir-Hinshelwood adsorption model was used for evaluation of kinetics, degradation rate and half-life time of the reaction and it was concluded that the mechanism of MO degradation involves charge transfer and plasmon resonance energy transfer (PRET) from these plasmonic NPs to the TiO2. On the other hand, the reusability studies revealed that the photocatalysts can be re-used for several cycles without losing its performance with a convenient magnetic separability. Finally, it is shown that the prepared photocatalysts is successfully applied for degradation of organic pollutant in real textile wastewater.

The ZnO-Polyaniline nanocomposites with ratios of 9:1, 8:2, and 7:2 were successfully synthesized using a grinding method in ethyl alcohol. The XRD, TEM, and SEM characterizations are used for the analysis of the nanocomposites. The entire three nanocomposites were degraded by methyl orange in the presence of visible light. We get the best results for ZnO-Polyaniline (7:3) catalyst. About 82 % degradation of methyl orange was observed below visible light within 140 minutes.

The surface of BiOCl nanosheets, prepared by a simple hydrothermal method, was decorated by carbon quantum dots (CQDs) through a microwave-assisted procedure. According to Diffuse Reflectance spectroscopy (DRS), light-harvesting properties improved significantly, which was explainable based on the bandgap of the final photocatalyst, 1.15 eV. Elemental analysis results coupled with scanning electron microscopy (SEM) images proved changes in the morphological characteristics after adding CQDs to the support; While in powder X-ray diffraction (XRD) patterns, there was no indication of further crystalline phases on the surface of BiOCl nanosheets. The photocatalytic performance of the nanostructures was evaluated by Congo red dye removal under visible light at room temperature. The photoreaction obeyed first-order kinetics with the rate constant of 0.011 min-1. According to the experiments, photodegradation was noticeably affected by catalyst dosage, dye concentration, and pH, which were all optimized. The photocatalytic performance of the prepared nanostructure was mechanistically discussed, considering the desirable role of CQDs towards reaching superior photoactivity.

In this study, a photocatalyst based on the combination of a polyoxometalate (12-tungstosilicic acid) and a nanoparticle (α-Fe2O3) was prepared to investigate its ability to degrade Tramadol from water samples. The structure, morphology, and functional groups of the synthesized photocatalyst (α-Fe2O3/ 12-tungstosilicic acid) were characterized using SEM images, EDX pattern, TEM image, FAM images, and FTIR spectra. Due to the high surface-to-volume ratio in nanoparticles and high intramolecular charge transfer by polyoxometalates, the combination of α-Fe2O3 nanoparticles and 12-tungstosilicic acid as a photocatalyst exhibits a high photodegradation efficiency in a suitable time toward the tramadol degradation. Besides, several factors affecting the degradation process of Tramadol with the prepared photocatalyst were evaluated using an experimental design method based on Box-Behnken design to reduce the number of experiments and study the interaction between the factors. In optimal conditions, the tramadol concentration, pH of the sample solution, photocatalyst amount, and the hydrogen peroxide concentration were optimized, which were 90.0 mg L-1, 300 mg L-1, 7.6, and 0.6 mg L-1, respectively. The study of the photocatalyst activity and the degradation kinetics for the tramadol photodegradation as a pharmacological contaminant in a water sample under ultraviolet irradiation exhibited that the synthesized photocatalyst had a high photodegradation efficiency with a pseudo-first-order rate constant of 0.0232 min-1 for a photodegradation time of 70 min.

Here, SnO2, BiVO4, and CuO nanoparticles (NPs) were hydrothermally synthesized and mixed in an agate mortar mechanically. The coupled ternary SnO2-BiVO4-CuO (SBC) catalyst and the individual NPs were then briefly characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM), and diffuse reflectance spectroscopy (DRS). Average crystallite size of 25 nm was obtained from the XRD data based on the Scherrer formula. The absorption edge (λAE) values of 1095, 430, 558, and 636 nm, corresponding to the band gap (Eg) values of 1.13, 2.88, 2.22, and 1.95 eV, were respectively obtained for the as-synthesized CuO, SnO2, and BiVO4 NPs and the as-prepared ternary SBC catalyst based on DRS results. The PZP degradation% of 11, 15, 17, and 24% were obtained by the CuO, SnO2, BiVO4 NPs, and SBC catalyst (with the same moles of each component). But, when the moles of BiVO4 in the SBC were two times greater than the others, about 43% of PZP were removed. The k-value of 9.9 × 10-3 min-1 corresponding to the t1/2-value of 70 min was obtained by applying the Hinshelwood plot on the photodegradation results. Photodegradation experiments were carried out in pH 5, CPhP: 3.35 ppm, and catalyst dosage: 0.55 g L-1. Further, when the photodegraded solutions were subject to the COD experiment, the Hinshelwood plots showed a slope of 0.01 min-1 which corresponds to the t1/2-value of 69.3 min.

Photocatalytic degradation of pollutants using the semiconductor Quantum Dots (QDs) can be applied to water treatment processes. In this paper, first, the Orange Peel (OP) and the Activated Carbon (AC) were prepared from the orange peel wastes. Second, CdS quantum dot-loaded adsorbents were prepared from these adsorbents and they were labeled as CdS@OP and CdS@AC, respectively. This new photocatalyst was characterized using FT-IR, FESEM, and UV-Vis. Then, the adsorption properties of these prepared adsorbents for the removal of alizarin, as an organic pollutant, were studied, and AC was selected as a better adsorbent for this purpose. Afterward, the photocatalytic properties of these adsorbents were also studied for the degradation of alizarin, under sunlight irradiation. A factorial design method was used to achieve the optimal condition and the best photocatalyst was selected. Finally, CdS@AC nanocomposite was selected as a more effective photocatalyst with the degradation efficiency of 82% of dye solution, under 2h sunlight irradiation.

In this work, ZrO2/TiO2/ZnO ternary nanocomposites were prepared by the sol-gel technique. The Taguchi method with the L9 orthogonal array was utilized to optimize the experimental conditions for the preparation of nanocomposites. The design has four factors, and each factor has three levels. The design factors of this study were calcination temperature, the aging time, the calcination time, and ultrasonic irradiation duration. Furthermore, as-synthesized structural features of nanocomposites were characterized, utilizing XRD, BET, FESEM, and EDX. The photocatalytic activities of all ZrO2/TiO2/ZnO nanocomposites were evaluated by the photodegradation of Congo red (CR) as an azo dye. The photocatalytic property of nanocomposites was enhanced by decreasing particle size and increasing the surface area. The best sample photodegraded 97% the CR solution within 15 min under an 8W UV lamp. The optimal conditions were achieved as 400 ºC calcination temperature, 72 h aging time, 4 h calcination time, and 30 min duration of ultrasonic irradiation for CR solution photodegradation. The effect of each parameter was evaluated using ANOVA analysis. The kinetics results showed the pseudo-first-order reaction mechanism for the photocatalytic activities of the nanocomposites.

The present work has for the main objective the elimination of the textile dye Maxilon Red (MR) by coupling two processes, adsorption on activated clay followed by photocatalysis over the wurtzite ZnO. The influence of the physical parameters like the initial pH, adsorbent dose of the activated clay, MR concentration, and temperature have been studied. The best adsorption yield occurs at neutral pH ~ 7 within 60 min with an adsorption percentage of 97% for MR concentration of 25 mg/L and an adsorbent dose of 0.5 g/L. The data were suitably fitted by the Langmuir model with a maximum adsorption capacity of 175 mg/g. To investigate the adsorption mechanism, the adsorption constants were determined from the pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. It was found that the MR adsorption is well described by the pseudo-second-order kinetic. The thermodynamic parameters ΔH˚ = -17.138 kJ/mol, ΔS˚ = 32.84 J/mol.K, and ΔG˚=−6.419 to−7.329 kJ/mol with rising temperature from 25 to 50˚C indicated that the adsorption is exothermic and spontaneous. The second part of this work was devoted to the photocatalytic degradation onto ZnO under solar irradiation of the residual MR concentration, which remained after adsorption. In this respect, the effect of ZnO dose and MR concentration has also been investigated. The photodegradation rate reached 99% under irradiation within 90 minutes under the optimum conditions. The parametric study showed that the elimination is very effective by photocatalysis, based essentially on the in situ generations of free radicals •OH which are non-selective and very reactive. The present study shows that the activated clay is an effective low-cost adsorbent for the removal of Maxilon red from an aqueous solution.