Sharif Digital Repository

To exert the optimum effect, the chemical exchange process to boron isotope separation was investigated. In this enrichment method the distillation of dimethyl ether-boron trifluoride complex, which was one of the most efficient industrial methods for purification of isotope boron-10, was optimized. In chemical exchange process of boron isotopes separation two chemical reactions occur. The first one is the decomposition reaction that is an endothermic reaction. The second one is the exchange reaction that is a pyrogenic reaction. With increasing temperature, the decomposition reaction is speeded while the exchange reaction is slowed down. Affecting on both decomposition and exchange... 

High chemical resistance is the main prerequisites for materials that are intended to be utilized in usages such as chemicals storage containers production. Nanocomposites of epoxy resin containing nanoclay, CaCO3 and TiO2 nanoparticles were prepared and their chemical resistance was studied. Moreover, the effect of electron beam irradiation was explored. TEM micrographs proved the dispersion of nano-size particles in the polymeric matrix. XRD patterns showed an exfoliated structure for nanocomposite containing 1 % nanoclay and intercalated structures for nanocomposites with higher nanoclay contents. SEM showed the pits that appeared in epoxy/nanoclay structure due to chemical corrosion.... 

By a single-step supercritical hydrothermal synthesis method, yttrium oxide nanoparticles were successfully prepared without additional treatment. Yttrium oxide nanoparticles were employed as an adsorbent to study the adsorption of some heavy metal ions. This study revealed that nano structure yttrium oxide was an effective adsorbent for removal of lead ions from aqueous solutions  

The current study aimed at application of the plain and supported platinum nanoparticles as a heterogenous catalyst for the reduction of aromatic nitro compounds. Monodispersed platinum nanoparticles were synthesized by reduction of H2PtCl6 by ethanol in the presence of polyvinyl pyrrolidone as a stabilizer, and then were immobilized on four types of zeolites. The obtained catalyst granules were characterized by X-ray diffractometry and transmission electron microscopy. The study then focused on elaboration of the catalytic activity of the nano catalysts under different operational conditions. It was found that reaction is adequately rapid at ambient temperature, and by utilizing a... 

The effects of varying operating conditions on metals removal from aqueous solution using a novel platinum nanopartcles/Zeolite-4A adsorbent are reported in this paper. Characterization of the adsorbent showed successful production of platinum nanopartcles on Zeolite-4A using 3 Wt% platinum. The effects of operation conditions on metals removal using this adsorbent were investigated. The optimal metals adsorption was observed at pH 7, 0.1 g/10 mL dosage and 30 min contact time. Sorption data have been interpreted in terms of Langmuir and Freundlich isotherms  

Gold nanorods (GNRs) can be used in various biomedical applications; however, very little is known about their in vivo tissue distribution by radiolabeling. Here, we have developed a rapid and simple method with high yield and without disturbing their optical properties for radiolabeling of gold rods with iodine-131 in order to track in vivo tissue uptake of GNRs after systemic administration by biodistribution analysis and γ-imaging. Following intravenous injection into rat, PEGylated GNRs have much longer blood circulation times. We have developed a rapid and simple method for radiolabeling of gold rods with iodine-131 in order to track in vivo tissue uptake of gold nanorods after systemic... 

The current study is aimed at comparison of adsorption behaviors of silica-supported Cu nanoparticles (Si-N-Cu) and micrometric copper powder (Mi-Cu) for uptake of iodine vapor. The Si-N-Cu was synthesized by the decomposition of aqueous Cu(NO3)2 solution at supercritical condition, followed by reduction of the sample by H 2-N2 mixture. The Si-N-Cu sample with 29.4 nm Cu particles adsorbed 95% of I2 at partial pressure 10-5 bar in 1 h, while the 1 μm Mi-Cu adsorbed 51% of iodine in 6 h, indicating higher yield and faster kinetics of the nanometric sample. Theoretical analysis revealed the existence of a strong thermodynamic size effect in the Cu-I2 reaction system, so that molar |ΔG| for 2... 

NaY zeolite nanoparticles were synthesized and shaped into the uniform spherical granules using a developed novel and simple two-step granulation technique. First, the alginate/nanozeolite or alginate/nanozeolite-bentonite spherical hybrid was successfully fabricated, and then the alginate was decomposed by calcinations resulting uniform spherical granules. To improve the mechanical stability of the prepared granules, bentonite was added as an inorganic binder at different ratios of 20wt.% to 40wt.%. Moreover, the effect of binder on the ion exchange properties of the prepared granules was studied. Increasing of binder content from 20wt.% to 40wt.% linearly enhanced the mechanical stability... 

Henry's law constant and crystal diffusivity of xenon in the granulated nano-NaY zeolite were measured by the pulse gas chromatography method. For this purpose the moments of response peaks of xenon were analyzed. The effect of extra column parts of the utilized chromatographic system was also considered by analyzing the moments of the response peak which was obtained by pulse injection of inert gas of helium into the carrier gas of nitrogen. In addition, the measurement of average velocity of the carrier gas regarding the pressure drop in the extra column parts of the system attributed to precise results. By carrying out the experiments at various temperatures in the range of 30-110 °C the... 

Thorium dioxide (thoria) nano-particle was synthesized by employing supercritical water (SCW) as an excellent reaction environment for hydrothermal crystallization of metal oxide particles. This method is ideal for production of ultrafine powder having controlled stoichiometry, high quality, purity and crystallinity. The nano-crystalline thoria was prepared in a stainless steel (316 L) autoclave, fed with an aqueous solution of Th(NO 3) 4.5H 2O as a reactant and took place under SCW condition up to 450 °C for 45 min. The product was recovered and characterized by X-Ray Diffraction (XRD), Thermal Gravimetry Analysis (TG/DTA) and Brunauer, Emmett and Teller (BET) surface area analysis. The... 

Ultra fine CuO nanoparticles In the range of 2 ± 0.2 nm were synthesized by the supercritical hiydrotliermal method in a batch reactor. Itwas demonstrated that elevating the pH of the Cu2+ precursor solution to around 6 (neutral condition) not only does not lead to excessive agglomeration of the particles, but also reduces particle size and in general promotes their nanoscale characteristics. Prepared nanoparticles were immobilized in the biopolymcric matrix of barium alginate and calcined at different temperatures resulting in micro spherical granules of high porosity and elevated mechanical strength. The fabricated samples were characterized using x-ray diffractometry (XRD), transmission... 

Recyclable CuO nanoparticles provide an efficient, economic, and novel method for the synthesis of quinoxaline, benzoxazine, and benzothiazine. This method provides a wide range of substrate applicability, avoids the use of organic solvents, and gives benzoheterocycles in satisfactory yields  

In this research, the characteristics of the prepared samples in epoxy matrix by means of X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), as well as scanning electron microscope (SEM) are evaluated. Meanwhile, the obtained mechanical properties of the specimen are investigated. Thermogravimetric analysis (TGA) is also employed to evaluate the thermal degradation of manufactured nanocomposites. The thermal neutron absorption properties of nanocomposites containing 3 wt% of montmorillonite nanoclay (closite30B) have been studied experimentally, using an Am-Be point source. Mechanical tests reveal that the higher B4C concentrations, the more tensile strengths, but lower... 

In the light of the novel physical-chemical properties of supercritical water as a green reaction medium, we studied the synthesis of deuterated benzene in supercritical heavy water, in the presence of sodium deutroxide, as a catalyst. The effects of operational parameters including temperature, time, pressure (density), catalyst amount and benzene/D2O volumetric ratio on the degree of deuteriation (D%) and deuterated benzene yield were investigated extensively and the conditions for the highest degree of deuteration and product yield, were optimized. Furthermore, because of the importance of the pressure of solution inside the reaction medium on the H/D exchange process as well as the... 

Vacuum residue cracking has been successfully conducted under supercritical water condition in presence of various metal oxide nanocalysts, namely NiO, CuO, ZnO, Co2O3, and Cr2O3 synthesized at supercritical water. The cracking experiments were carried out at 450 °C. Three species of cracking: maltene, asphaltene, and coke were then weighed and their corresponding speciation was defined. Gas chromatography-mass spectrometry (GC–MS), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA), and elemental analysis (CHNS) tests were utilized to prove the performance of upgrading reactions. It was revealed that NiO showed the best performance among other catalyst, in which... 

Tributhyl phosphate (TBP) decomposition in supercritical water oxidation (SCWO) was performed with and without catalyst, at different temperatures ranging from 370 to 480 °C, and different reaction times. Ag2O, CuO, Fe2O3, MgO, and ZnO synthesized by supercritical water were examined in TBP decomposition as the catalyst. TBP structure decomposed under the non-catalytic reaction; nevertheless, the results indicated that the use of catalysts improved the reaction efficiency, which calculated based on total organic carbon (TOC) removal, by far. However, TOC removal using Fe2O3 was 20% higher than the non-catalytic reaction. Having the ability in completion of the redox cycle, iron oxide... 

A comparative study on the uptake properties of alginate microcapsules containing Cyanex 302 extractant, Lewatite TP 214 chelating resin, and Amberlite 200CT strongly acidic ion exchanger has been conducted using Ag+ as the target ion. The study resulted in an analytical formula, as well as three phenomenological breakthrough formulas that are also applicable in other fixed-bed operations. It also demonstrated a close similarity of the uptake properties of alginate microcapsules (MCs) and the chelating resins. Advantages of MCs over chelating resins include ease of preparation, ability to immobilize different extractants, and, most remarkably, an enormous distribution factor (Kd ≈ 106... 

In this work, molecular dynamic simulation of the mixture of imidazolium based ionic liquids with alcohols is implemented in order to investigate mixing excess properties and some structural and physical properties of the mixture. Excess volumes and enthalpies are evaluated for 11 different mole fractions of ionic liquids at each 0.1, in the range of 0 to 1. Radial distribution function, cohesive energy density, potential of mean force, solvation energy, and diffusion coefficient are reported and analysed. The effects of the cationic alkyl chain length, in comparison with changes of the anions, on these properties are reported. Results reveal that the methanol molecule participates with its... 

The current study presents a simple and scalable method for the synthesis of (aminomethyl)phosphonic acid-functionalized graphene oxide (AMPA-GO) adsorbent. The chemical structure of the new material was disclosed by different instrumental analyses (e.g. FTIR, Raman, XPS, AFM, TEM, XRD, CHN, and UV), and two pertinent mechanisms namely nucleophilic substitution and condensation were suggested for its formation. Adsorption experiments revealed that both AMPA-GO and plain GO have a high affinity toward Th(IV) ions, but the AMPA-GO is superior in terms of adsorption capacity, rate of adsorption, selectivity, pH effect, etc. Indeed, the AMPA-GO can uptake Th(IV) nearly instantaneously, and... 

The current study presents a simple and scalable method for the synthesis of (aminomethyl)phosphonic acid-functionalized graphene oxide (AMPA-GO) adsorbent. The chemical structure of the new material was disclosed by different instrumental analyses (e.g. FTIR, Raman, XPS, AFM, TEM, XRD, CHN, and UV), and two pertinent mechanisms namely nucleophilic substitution and condensation were suggested for its formation. Adsorption experiments revealed that both AMPA-GO and plain GO have a high affinity toward Th(IV) ions, but the AMPA-GO is superior in terms of adsorption capacity, rate of adsorption, selectivity, pH effect, etc. Indeed, the AMPA-GO can uptake Th(IV) nearly instantaneously, and...