جستجوی مقالات مرتبط با کلیدواژه « photocatalyst » در نشریات گروه « محیط زیست »

Naphthalene is one of the toxic and dangerous polycyclic aromatic hydrocarbons (PAHs) for human and the environment, and it is necessary to remove it from the environment. The aim of this research is to investigate the phothocatalytic degradation of naphthalene from aqueous environments using two nanocatalysts TiO2-N, S/SiO2 and TiO2-P/SPA under visible light in the presence of Oxygen.  
Material and This research was done in year 2019.  In this research, two phothocatalysts TiO2-N, S/SiO2 and TiO2-P/SPA were synthesized by sol-gel method and they were used to remove Naphthalene from the aqueous environments under visible light and in the presence of Oxygen.  The Effect of various parameters including the initial concentrations of naphthalene, pH, contact time were investigated, and the structure of these nanoparticles was investigated using scanning electron microscopy (SEM), energy-dispersive ray (EDAX) image and UV-Vis differential reflectance spectroscopy (DRS) analysis.
SEM image showed the nanoparticle size of synthetic phothocatalysts to be 10 to 20 nm and, the thickness of the phothocatalyst thin layer TiO2-N, S and TiO2-P on the microspheres was 698.68 nm and 1.73 µm, respectively. DRS analysis indicated that the energy band gap of both phothocatalysts has become narrower than TiO2 and their phothocatalytic activity has been transferred to the visible light region. In the optimal conditions of Naphthalene removal, the values of pH, time, Naphthalene concentration, and removal efficiency were obtained for TiO2-N, S equal to 5, 50, 25, 94.23% and for TiO2-P equal to 5, 40, 25, 97.39%, respectively (Pv<0.05).
Discussion and These photocatalysts can be used as a new, effective and practical method in the treatment of water and wastewater from industrials containing Naphthalene under sunlight and visible light.

CuO dandelion-like microspheres were synthesized using a simple and green coprecipitation method. As-prepared CuO microspheres were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and diffuse reflectance spectroscopy (DRS). The photocatalytic activity of this nanostructure on the degradation of dye pollution of methylene blue with different concentrations between 10-50 mg/L in presence of H2O2 was investigated under 7 W LED lamp. The studyof results shows that the amount of of degradation of methylene blue is low in the absent of H2O2, and afteradding H2O2, it significantly increased. The amount of required H2O2 was studied. It was found that synthesized nanocatalyst in the presence of a very small amount of H2O2 (50 μL), has the ability to destroy 100% of methylene blue with 20 mg/L concentration.

Recently, the degradation of organic pollutants using novel semiconductors with strong absorbance for broad ranged visible lights has generated broad interest of photocatalysis. In the last few years, perovskite-type bismuth ferrite (BiFeO3, BFO) has received a lot of attention. BiFeO3 is one of the rare well-known multiferroic compounds with a rhombohedrally distorted perovskite structure of space group R3c that exhibits ferroelectric and antiferromagnetic properties at room temperature. The narrow band gap and high chemical stability of BiFeO3 make it an effective photocatalyst in the visible light region during the photocatalytic process. BiFeO3 nanopowder was synthesized via a microwave-assisted combustion method by using acetic acid as fuel, for the first time. The structural characterization showed that BiFeO3 was almost pure perovskite type. A ferromagnetic hysteresis loop with a saturation magnetization (MS) of 0.66 emu/g has been observed at room temperature in the sample. The small band gap (=2.08 eV) of prepared BiFeO3 indicates a possibility of utilizing much visible light for photocatalysis. Photocatalytic test for degradation of methyl orange dye indicated that BiFeO3 exhibited high photocatalytic activity.

Everyday million liters of color wastewater are produced in different industries and cuases environmental problems. The textile industry significantly affects the environment, producing high volume of wastewater from water and chemicals used in processes including sizing, washing, bleaching, dyeing, printing, and finishing. The wastewater contains salts, acid, or alkali, washing solvents, other chemicals, intermediates, and residue dyes. In the presence of toxic colored substances in water light fails to penetrate the waters lower layers and consequently the photosynthesis of water plants and the level of dissolved oxygen decreases, and results in the death of aquatic life. Dyes are stable compounds that are not easily biodegradable; especially Azo dyes which are considered to be carcinogens that pollute the surface and groundwater.
Generally, the physical, chemical and biological methods or a combination of them have been used for treating textile wastewater can be mentioned as membrane filtration, and ultrasonic waves, electrocoagulation, adsorption, Fenton, photo-Fenton, ion exchange, electrolysis, coagulation, conventional, and advanced oxidation and photo-catalytic process.
In recent years, the ability of advanced oxidation processes in treating various hazardous wastes has brought this technology to the forefront of research. Among advanced oxidation processes, application of heterogeneous photo-catalysis by using semiconductors has been proved to be real interest as an efficient tool for degrading both aquatic and atmospheric organic contaminants. Semiconductors are photo-reactive metal oxides for contaminants eradication that refer to photo-catalysts. These methods mineralize and converse pollutants into CO2, H2O and inorganic ions, by the action of hydroxyl radical, which acts as a nonselective and strong oxidant of organics.
Because of the excellent properties and wide applications on nanomaterials, recent years, researchers start to focus on the nano-zinc oxide granule size lies in the 1-100 nms, because of having nanophase structure and char acteristics, it gets the surface effect and bulk effect and gains some special capabilities (on magnetism, light, electric and sensitivity etc.) and many new usages.
Photocatalytic reactors for water and wastewater treatment can be classified to slurry and immobilized systems. In the slurry reactors, the nano particles are freely dispersed in the water phase and consequently the photo-catalyst is fully integrated in the liquid mobile phase. Whereas the immobilized catalyst reactor design features a catalyst anchored to a fixed support and dispersed on the stationary phase.
The mail aim of this sudy was to compare removal efficiency of acid orange 7, one of the high consumed textile dyes, in slurry and immobilized methods using photocatalyst UV/ZnO process.
Methods and materials: In this study, after detrmination of the maximum absorption wavelength of acid orange 7 (Table 1), the initial experiments were done to determine the main role of photocatalyst process (Figure). Then the effect of different amounts of dye concentration and catalyst, pH, irradiation power and energy consumption were investigated and optimized for both slurry and immobilized systems by changing one papramter and keepig the others constant.
The Water Sealer Method (WSM) was used to immobilize the nano ZnO powder on concrete surface. The process began by complete mixing of 100 mL of selected concrete sealer (colorless liquid) with measured amounts of ZnO. To the cured concrete surface of one reactor, 10 mL of 10% (by mass) ZnO sealer solution was prepared and put into ultrasonic cleaner (Fungilab UE-6SFD) for 5 min to ensure the complete separation of nano particles. Then the solution was applied and allowed to be cured for at least 3 d.
Table 1 Characteristic of Acid Orange 7
Structure
Formula C16H11N2NaO4S
Molar mass 350.3243
λmax 487 nm
Solution pH 3
Slurry and immobilized photo-catalyst reactors
According to the Beer Lambert law, by measuring the absorbance of samples at the maximum absorption wavelength of the dye (487 nm) in a spectrophotometer, dye concentration and removal rate (Eq. 1) were calculated, where CR was color removal efficiency (%), C0 represented initial dye concentration, and C indicated instant dye concentration. In order to eliminate flocs errors, samples were filtered and centrifuged prior to placing them in the spectrophotometer.
(1)
The main equipments used in this study include a Kern PLS 360-3 digital scale with 0.001 accuracy and Metrohm 691 pH meter. The amount of dye in solution was measured by using a Hach DR-4000 spectrophotometer at a wavelength of maximum absorption of acid orange 7 (485 nm) and the calibration curve of dye concentrations, respectively. All experiments were performed according to the method of analysis of water and wastewater and repeated at least 3 times.
In summary, acid orange 7 could be successfully degraded and mineralized by nanophotocatalysis in both slurry and immobilized ZnO nanoparticle photocatalytic reactors.
The experiments in optimum conditions in both slurry and immobilized methods were shown that in pH of 7, catalyst concentration of 80 gr/m2 (10.32 gr/L) and 32 Watt UVc lamps, over 95 and 35 percent of 50 ppm dye was removed in slurry and immobilized methods, respectively. The amount of COD removal was higher in the slurry method (Table 2).
Table 2- Comparison of optimum conditions in the studied systems
Immobilized System Slurry System parameter
80 gr/m2 10.32 gr/L Catalyst Concetration
50 50 Dye Concentration (ppm)
7 7 pH
32 32 Power (Watt)
375 56 Time
4 6 COD Removal after 60 minutes
35 45 COD Removal after 375 minutes

Petroleum is a complex mixture of hydrocarbons contain thousands of harmful effects that due to the relatively high volume of entering the aquatic environment, reducing pollution caused by it is very important. The aim of this study was to investigate the removal of toxic components of crude oil by nanoparticles of titanium dioxide under UVradiation. The study was conducted on hydrobiology aquatic propagation lab of Khatamolanbia University of Behbahan. 210 specimens of Cyprinus carpio (average weight = 54.4 ± 8.43, average total length= 15.4 ± 0.53) were purchased from a private aquaculture center and acclimation was done for two weeks in 300 liter tanks. Standard solution phase synthesis of crude oil and titanium dioxide nanoparticles by mixing one part Petroleum with 9 parts titanium dioxide nanoparticles were prepared. Then the fish were treatmented in group 7 (with three replications) consisting of 10 specimens randomly. In the days zero and 21 fish specimen per tank number of 3 was taken randomly and evaluate each fish separately with digital scales and bioassay was conducted with the board. Then anatomy the fish and entrails, which each weighed separately. The results showed that titanium dioxide nanoparticles both visceral for treatment and solution phase petroleum under ultraviolet radiation and titanium dioxide nanoparticles and the feed conversion ratio for oil treatment solution phase crude oil under darkness control group showed a significant increase (p<0.05). Based on the results of this study, it can be said that the process of photocatalytic titanium dioxide and Ultraviolet radiation lead to a reduction in the adverse effects of poorly soluble phase was crude oil.