tio2

"Phenol and its water-soluble derivatives are among the most important toxic pollutants. In recent years, the use of MOFs as photocatalysts for wastewater treatment has attracted much attention. Combining a MOF with a semiconductor that can minimize electron-hole recombination can be very effective in photocatalytic reactions."

In this research, TiO2/MIL88 composites with different percentages of titanium dioxide were synthesized using a one-pot hydrothermal method and investigated for phenol removal in a hexagonal photoreactor. The unique hexagonal design of the reactor increases the surface area available for radiation, resulting in more effective removal of contaminant. In order to achieve the highest degradation efficiency, the variables: amount of photocatalyst, reaction time, phenol concentration, pH, and H2O2 concentration (ml/L) were selected as effective parameters on the photocatalytic degradation process. In order to design the experiments, Design Expert software was used, and among the RSM methods, Box Behnken method was selected.

Catalyst characterization analyzes showed that TMA10 composite was correctly synthesized. Using this composite, the optimal conditions for the maximum efficiency of phenol degradation (95.96%) are as follows: initial concentration of phenol 58 mg/L, pH equal to 7.51, reaction time 68.61 minutes, H2O2 concentration equal to 0.18 mL/L, and the amount of catalyst equal to 0.4 g/L was obtained.

The results of photocatalytic experiments showed that TMA10 composite (10 molar ratio TiO2:MOF) has a better performance than other composites in phenol degradation. Photoluminescence (PL) analysis showed that the better performance of TMA10 composite is due to the reduction of electron-hole recombination in it. Also, analysis of variance showed that the quadratic model fits well with the data.

The main purpose of this study is the oxidation of carbon monoxide to carbon dioxide in the presence of copper catalyst.  This odorless gas needs to be removed somehow because it is toxic. Oxidation methods include carbon dioxide oxidation and hydrogenation.  At present, the second method is interesting for researchers as a key technology to produce clean fuels and chemicals.  Copper catalyst was selected because of its cheapness and suitable activity in the carbon monoxide oxidation reaction.  In this study, the effect of different bases on product selectivity and feed conversion rate was investigated.  In this dissertation, first copper nanoxides were prepared by co-precipitation and microemulsion method and then the final catalyst was obtained by wet inoculation (copper on different bases).  Catalysts are evaluated in terms of physical and chemical properties, and in certain operating conditions of temperature (100-400 °C), pressure (1 atm), feed volume ratio (O2</sub> / CO / H2</sub> / N2</sub> = 2/2/5/91 and GHSV= 1.5-6 nl.h-1.gCat-1 valley fixed bed reactor system was tested.  The results of the reactor test show that TiO2</sub>-based copper nanocatalyst has a higher rate of carbon monoxide conversion and selectivity.  Increasing the lanthanum enhancer to the catalyst structure increases the conversion rate of carbon monoxide and the selectivity of carbon dioxide.

Nanomaterials are substances that, because of their size, can easily penetrate small pores and apply their impact. Nanofluids can allow appropriate wettability change in the reservoir rock, therefore, an accurate understanding of the behavioral mechanisms of these nanofluids is important in changing the wettability. This is because if there is no proper understanding of these mechanisms, they may exhibit the opposite behavior and cause damage to the reservoir. In previous research, CuO / TiO2 / PAM nanocomposite was synthesized and mechanistically introduced.

In this study, in continuation of the previous study, the behavioral and mechanism study has been investigated in a more accurate and documented manner, and spectral absorption tests, chemical flooding, and relative permeability diagrams confirm the effectiveness of enhanced oil recovery results of this nanocomposite. In carbonate rocks due to the positive surface charge of the rock and the negative charge of the nanocomposite, adsorption of nanomaterials in a double electrode layer state has been suggested as the dominant mechanism of wettability change. In sandstone rocks due to the charge coincidence of rock surface and nanomaterials which are both negative, the mechanism of disjoining pressure was the dominant mechanism of wettability change. To prove the abovementioned behaviors 200 ppm concentration of nanofluid was analyzed by spectroscopy method of adsorption analysis to validate the attraction forces of the nanocomposite with carbonate rocks and repulsion forces with sandstones.

Dynamic chemical flood tests were performed to confirm the effectiveness of this material in increasing oil production and showed 8.5% and 6.35% increase in oil production for carbonate and sandstone lithologies, respectively. Relative permeability diagrams showed an intersection point in the carbonate system with a 10% increase in water saturation and an intersection point in the sandstone system with a 12% increase in water saturation and the behavioral effect of the material at the studied concentrations.

The aim of this work was to achieve of technological knowledge of production of antimicrobial nanocomposite packaging containing nanoparticles in order to increase the shelf life of apple and grape fruits. Low density polyethylene (LDPE) was chosen as base polymer and titanium dioxide (TiO2, 0, 0.5 and 1.5%) and zinc oxide (ZnO, 0, 0.75 and 1.5%) nanoparticles were added to LDPE matrix to produce nanocomposites by extrusion method. At the first step, the effect of nanoparticles addition on physicochemical properties of nanocomposites were investigated. It was revealed that the antimicrobial analysis showed that the nanocomposite films have good bactericidal activity and the effect of titanium dioxide is more than zinc oxide nanoparticles. At the second step, fabricated films were used for packaging of fresh apple and grape fruits. The qualitative parameters of fruits were investigated during this period. Results indicated that the weight loss of fruits decreases by using nanocomposites. Browning index and also, hardness of apple products in nanocomposite packaged samples were more than control ones. Nanocomposite films controlled the microbial count of apple and grape and the film containing 1.5% titanium dioxide showed the most effect on mesophilic bacteria and yeasts and molds. Generally, titanium dioxide was more effective than zinc oxide in both of improving physical properties of nanocomposites and increasing the shelf life of apple and grape fruits. Resoles of this research approved that the using of LDPE nanocomposite active film containing titanium dioxide and zinc oxide nanoparticles could be a good way for increasing the shelf life of apple and grape during production and distribution.

Annually, insoluble biodegradable dyes in textile, leather, paper and food industries, photovoltaic cells are evacuated to natural water flows. The highly ordered TiO2 nanotube arrays made with titanium anodizing, due to its large surface area, strong oxidizing ability and excellent charge transfer performance, have been widely used as photocatalyst for decomposition of dyes in recent years. Nevertheless, the disadvantages of TiO2 are the vast energy gap (3.0-3.2 eV) and the high recombination of electron-hole derived from light that limits the use of TiO2 nanotubes in the use of visible light to decompose organic pollutants. For this purpose, in recent years, many attempts have been made to modify TiO2 nanotubes to increase light absorption to visible light, limit the band gap, increase surface area, and prevent the recombination of charge carriers. To overcome these limitations and increase photocatalytic activity of nanotubes, various methods have been investigated: decoration with noble metal particles, doping with metal elements, modification with semiconductor and doping with non-metallic elements.

Nowadays, due to the increasing problems caused by global warming, researchers have proposed several methods to reduce carbon dioxide emissions in the atmosphere. Among the conventional methods, the processes of Carbon Capture and Storage (CCS) and carbon dioxide conversion to useful products are great of importance. Meanwhile, photocatalytic conversion of CO2 to valuable chemicals and hydrocarbon fuels, not only reduces concerns about the accumulation of this polluting gas but also creates a new pathway for the synthesis of carbon-dioxide derived compounds. This review article at first briefly studies carbon dioxide conversion technologies and then discusses the principles of carbon dioxide photocatalytic conversion. The main purpose of this paper is to investigate the effects of reducing agents among the various factors affecting the photocatalytic conversion of CO2. Therefore, the effects of different reducing agents such as liquid water, steam, and hydrogen gas on carbon dioxide conversion and product distribution are studied. The results of this study indicate that various reducing agents cause different reaction mechanisms, and ultimately lead to the production of various products such as methanol, methane, formic acid, formaldehyde, and carbon monoxide. Next, in order to create the optimal conditions for conducting a reaction toward the desired product distribution with the highest yield, several reactions performed in the presence of these three reducing agents are compared. The selectivity of the conversion reaction is higher toward methanol in the presence of water. It means methanol is produced at a higher rate. However, the major products of photocatalytic reduction of carbon dioxide in the gas phase and in the presence of water vapor and hydrogen are methane and carbon monoxide.