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

Among the methods used to remove heavy metals are membrane processes that, with less use of chemicals, are able to quickly produce high-quality penetration. In this study, a nanocomposite membrane with the ability to separate lead was used. The black titanium dioxide nanoparticle was synthesized using the pyrolysis method. Adsorption experiments were performed using a nanofiltration unit. The results of lead adsorption isotherms showed that the lead adsorption process using the membrane follows the Langmuir model with a correlation coefficient of 0.995. The results of the study of lead metal adsorption kinetics showed that the process of adsorption of lead by the adsorbent follows the quasi-second order kinetics so that the correlation coefficient of the second-order quasi-model is equal to 0.999 which is compared with the quasi-correlation coefficient. The maximum and minimum fluxes between different membranes were related to 0.1 mg/l of titanium dioxide nanoparticles in terms of time and pressure for 50 and 600 minutes and pressures of 45 and 145 bar, with increasing the initial concentration of pollutants, the percentage of adsorption decreases. This can be due to the delay in balancing the adsorbent and the contaminant.

Denitrification of drinking water has a research history of more than three decades in the field of water treatment and is still the subject of many research projects. The main purpose of this study is to obtain or modify methods for removing nitrate from drinking water in an economic way and force minimal adverse effects on the environment. The use of photocatalytic process for denitrification is not new, but there are still many ambiguities. In this study, the feasibility of using two different photocatalysts over the ultra-high performance concrete (UHPC) substrate was discussed. This new substrate is fabricated by immobilizing the photocatalyst inside a cement matrix which acts as an active layer over the UHPC surface. Optimum long-term lifecycle and higher efficiency of this active surface is achieved without a significant drop of the photocatalyst activity near the surface. In this study, the possibility of using photocatalytic composite layers over the elements made of UHPC for applications such as water supply channels was evaluated and the challenges of using such layers on UHPC surfaces were described. According to the studies, it was found that the use of fixed cement composite bed for photocatalytic treatment has advantages over other methods of photocatalytic water treatment.

One of the main applications of titanium dioxide nanoparticles is killing the microorganisms spatially in drinking water and wastewater treatment.

  Pure bentonite/Titanium Dioxide nanocomposites and doped with 3, 5 and 10% w/w silver were prepared by molten salt method. In this study, the antibacterial activity of silver doped titanium dioxide/bentonite nanocomposites was studied against two important microorganisms in food industry i.e. Escherichia coli and Staphylococcus aureusunder visible or UV radiation. The photocatalytic activity of these composites against methyl orange was also investigated. The prepared nanocomposites were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX), UV-Vis diffusive reflectance spectrometer (UV-Vis DRS).

The scanning electron microscope was showed, that agglomeration of spherical TiO2 nanoparticles formed on the bentonite surface. The XRD pattern revealed that all of the samples have only an anatase phase with crystalline size less than 50 nm. According to EDX analysis, the silver ions successfully doped to the TiO2 nanoparticles. According to UV-Vis DRS results, increasing amounts of doped Ag content in the silver-doped titanium dioxide results in a higher visible absorbance capability of the materials. Parent bentonite did not show antibacterial activity. Titanium dioxide/bentonite nanocomposites showed very weak antibacterial activity. The results showed that the antibacterial ability was significantly improved by doping silver content comparing with pure TiO2/bentonite nanocomposites. This study also showed that Gram-positive bacteria (S. aureus) were more readily disinfected by the photo catalysts than a Gram-negative bacterium (E. coli). According to photocatalytic activity findings, doping of nanocomposites with 5 % silver ions showed maximum photocatalytic activity. This is attributed to the increasing visible absorption capacity due to the presence of silver ions.

Antibacterial and photocatalytic activity of titanium dioxide/bentonite nanocomposites increases dramatically due to the addition of silver ions. This can be attributed to the release of silver ions from nanocomposites and the increase in the production of free radicals as a result of increased photocatalytic activity due to reducing the energy gap of titanium dioxide nanoparticles in nanocomposites.

Dye is considered as one of the most important environmental pollutants in industrial wastewater due to its harmful effects on both human and environment. This study was aimed to determine Optimum Dioxide Titanium Nanoparticles in Dioxide Titanium /Bentonite Composite for sono photo catalytic de-colorization of Methyl Orange dye. 

In this study, bentonite was used as the substrate to stabilize titanium dioxide photo catalyst and the optimum amount of stabilized titanium dioxide nanoparticles in titanium dioxide/ bentonite composite was evaluated for sono photo catalytic removal of methyl orange dye. Accordingly, the optimal conditions for the photo catalytic process performance in dye removal included the effect of pH, methyl orange concentrations and nanocomposite doses.

Structural properties of bentonite/titanium dioxide composites and pure titanium dioxide nanoparticles were investigated using scanning electron microscope (SEM), Diffuse Reflectance Spectroscopy (DRS) and Xray diffraction (XRD). Finally, the possibility of reuse of photo catalyst was investigated in three periods. Based on SEM results, reducing the amount of titanium dioxide reduced the number of nanoparticles formed on the bentonite surface. XRD and DRS analyses showed successful composite formation. The optimum amount of titanium dioxide nanoparticles in titanium dioxide/bentonite composite was obtained for sono photo catalytic dye removal of methyl orange with the titanium dioxide powder to bentonite ratio of 1: 2.5 in the primary mixture.

  The study showed that increasing the amount of photo catalyst in the reaction medium increased the speed and efficiency of the dye removal but its excessive increase had a negative effect on the reaction. The best conditions for dye degradation were obtained using titanium dioxide/bentonite nanocomposite at pH 4. According to the results, the increase in concentration increased dye removal time. Finally, the sono photo catalytic composite efficiency was acceptable after three times of reuse.

 Due to the high use of polystyrene in food and medicine industries, it is particularly important to have antibacterial properties for these types of polymers. In this study, composite samples of polystyrene and titanium dioxide were prepared by using a twin-screw extruder.

 The samples were prepared by injection moulding process for mechanical and anti-bacterial testing. It was observed that adding TiO2 would improve the mechanical and thermal properties of polystyrene.

 According to the results of the natural weathering test, TiO2 as a semi-conductor photo-catalyst has an active role in the determination of antibacterial properties of polymer matrix.

  Micro and nano-scale of TiO2 improved impact strength, tensile strength, Vicat softening temperature and melt flow index of all samples. Moreover, the prepared mixture showed appropriate antibacterial properties against E.Coli and S.Aureus. It was concluded that the antibacterial properties of the nanocomposite sample are better than those of the composite sample because of smaller size and larger surface area of Nano particles.

Dye  is  considered  as  one  of  the  most  important  environmental  pollutants  in  industrial wastewater due to its harmful effects on both human and environment. This study was aimed to determine Optimum Dioxide Titanium Nanoparticles in Dioxide Titanium /Bentonite Composite for Sono-photocatalytic de-colorization of Methyl Orange dye. 

In this study, bentonite was used as the substrate to stabilize titanium dioxide photo-catalyst and the optimum amount of stabilized titanium dioxide nanoparticles in titanium dioxide/ bentonite composite which was evaluated for sono-photocatalytic removal of methyl orange dye. Accordingly, the optimal conditions for the photocatalytic process performance in dye removal included the effect of pH, methyl orange concentrations and nanocomposite doses.

Structural properties of bentonite/titanium Dioxide composites and pure titanium dioxide nanoparticles were investigated using scanning electron microscope (SEM), Diffuse Reflectance Spectroscopy (DRS) and X-ray diffraction (XRD). Finally, the possibility of reuse of photo-catalyst was investigated in three periods. Based on SEM results, reducing the amount of titanium dioxide reduced the number of nanoparticles formed on the bentonite surface. XRD and DRS analyses showed successful composite formation. The optimum amount of titanium dioxide nanoparticles in titanium dioxide/bentonite composite was obtained for sono-photocatalytic dye removal of methyl orange with the titanium dioxide powder to bentonite ratio of 1: 2.5 in the primary mixture.

  The study showed that increasing the amount of photo-catalyst in the reaction medium increased the speed and efficiency of the dye removal but its excessive increase had a negative effect on the reaction. The best conditions for dye degradation were obtained using titanium dioxide/bentonite nanocomposite at pH 4. According to the results, the increase in concentration increased dye removal time. Finally, the sono-photocatalytic composite efficiency was acceptable after three times of reuse.

Malachite greenis an extensively used biocide in the aquaculture industry, and is highly effective against important protozoal and fungal infections. It is also used as a food coloring agent, food additive, and medical disinfectant as well as a dye in the silk, wool, jute, leather, cotton, paper, and acrylic industries. Therefore, the elimination of malachite green in wastewater of aquaculture and textile, paper and acrylic industries is essential in order to prevent its adverse effects on aquatic organisms. In this study, degradation of malachite green with titanium dioxide nanoparticles (TiO2 NPs) under UV light was investigated.

For this reason, the effects of parameters such as different concentrations of malachite green (3.5, 7 and 14 mg L-1) and the Nano-catalyst concentrations (1.30, 2.60, and 5.20 mg) in constant temperature (25°C) and constant UV intensity (12 W, 230 V, 50 Hz) during 180 minutes were studied.

The best degradation rate of malachite green was found in the concentration of 3.5 mg L-1 malachite green, pH: 9, and 2.60 mg of TiO2 NPs. Although with an increase in titanium dioxide nanoparticles the efficiency and removal rate of malachite green increased, the increase in the photo catalyst had no effects on increasing the efficiency of photo degradation. An increase in pH (9) may improve the removal rate of malachite green through increasing free radicals. An increase in the initial concentration of malachite green decreased the efficiency and removal rate of malachite green.

Therefore, the photo degradation of malachite green in the presence of TiO2 NPs photo catalyst could be a function of pH, the initial concentration of malachite green and concentration of TiO2 NPs.

The aim of the present study is to compare the effects of titanium dioxide in nano scale and bulk form in gill, liver and intestine tissues of zebrafish (Danio rerio). In this study About 150 zebrafish exposed to static-renewal condition of TiO2 particles treatment. These nanoparticles and bulk titanium dioxide in concentrations of 1 and 10 mg.l-1 and a blank group in three replicate for 30 days. After the period of treatment (30 days) the fishes were stabilized in formalin and stained for further classic Histological studies. The results indicated that TiO2 in nanoscale and bulk forms can result in   epithelium separation, edema, hyperplasia, adhesion in lamella and Hyperemia, hypertrophy in filament of zebrafish (Danio rerio).  Also  abnormalities as cytoplasmic vacuolization, increase of melanomacrophage centers,  congestion and hepatocyte degeneration were observed in liver and injuries such as epithelium separation, increased and inflammation of goblet cells, necrosis and hyperemia in intestine tissue of zebrafish. The findings also suggested that nanoparticles induced more severe abnormalities in comparison with their bulk counterparts. Also, most of the mentioned abnormalities are dependent to the materials concentration. So, the severity of abnormalities was highest at 10 mg.l-1 concentration of the titanium dioxide nanoparticles compared with other treatments.

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.

Metallic powders have an important role in detection and pollutant remediation from environment. In this way, iron nanoparticles has served as a new material for environmental remediation. Therefor an economical solutions for many environmental challenges in the fields of pollutants elimination have been invented. Metallic oxide such as TiO2 in a nanometric scale as a cheap material, have ability for using in photocatalytic process and remediation. In this article in addition of reviewing the properties of metallic and oxide nanoparticles in environmental remediation process, remediation process by metallic iron nanoparticles was investigated and for instance, the remediation process of hexavalent chromium with these nanoparticles have been illustrated