نشریه شیمی و مهندسی شیمی ایران
سال سی و چهارم شماره 4 (پیاپی 78، زمستان 1394)

The synthesis methods for titania/ titanate nanotubes can be split into two categories: template and non-templated procedures. The templates can be classified into positive and negative (include: oregano gelator, macroporous alumina membranes, carbon nanotubes, surfactant) that synthesized nanotubes with diameters > 50 nm. The non-templating methods include alkaline hydrothermal, anodization of titanium in fluoride bathing, seeded growth. The key to developing
and exploiting new nanostructured materials lies in an improved knowledge of how synthesis conditions affect properties of nanostructured materials in order to tailor materials to specific needs, In particular, a knowledge of the mechanism of nanostructure formation is very important. In this paper, synthesis methods, microstructure, mechanism of formation and growth and their advantages and disadvantages for these nanotube reported by researchers are reviewed. The nanotube morphology, the highly surface area, and pore volume, render titania/titanate nanotubes promoting materials for many applications in different fields which include energy conversion and storage, catalysis, electro catalysis, photo catalysis, magnetic materials, drug delivery, bio-applications, composites, surface finishing, tribological coatings.

Cadmium as heavy and toxic metal is commonly found in water resource. It has made significant environmental issue. In this research, zinc oxide nanoparticle was prepared by sol-gel method, it was also evaluated with XRD, SEM techniques. Factors relevant to absorption processes such as the concentration of initial ion and temperatures were investigated. As a result, increasing the concentration and temperature, lead to increase, and decrease the absorption respectively. Thermodynamics of adsorption of cadmium (II) on zinc oxide nanoparticle at different temperatures were studied. Therefore, thermodynamic factors were shown that the absorption process was spontaneous, exothermic and reversible. The obtained absorption isotherms obviously showed that Langmuir model preferable than other models.

TEOS xerogel was investigated as adsorbent to removal strontium ion from aqueous solution in batch operations. Batch experiments were carried out as a function of pH, initial concentration, time, and temperature. Simple kinetic and thermodynamic models have been applied to the rate and isotherm sorption data and kinetic and thermodynamic parameters were determined. These studies were showed that the Langmuir isotherm model and pseudo-second-order kinetic model were fitted well with experimental data. The maximum capacity of the adsorbent for Sr(II) is 17 mg/g. The paper discusses the thermodynamic parameters of the adsorption (the Gibbs free energy, entropy, and enthalpy). Results demonstrate that the adsorption process was spontaneous and endothermic under natural conditions.

In this work, Vapor-Liquid Equilibrium (VLE) of the 3-component system composed of carbon dioxide (1), water (2), and methyl diethanolamine (3) has been modeled by the cubic plus association equation of state in a wide range of temperatures (313 –433 K), pressures (0.775 –4,930 kPa), and methyl diethanolamine wt% (5 –75). The 3-component system composed of carbon dioxide, water, and methyl diethanolamine was modeled by two different approaches. In the first approach, binary interaction coefficient between carbon dioxide and methyl diethanolamine was set equal to zero and energy and volume of association between carbon dioxide and methyl diethanolamine were optimized. In the second approach, the average energy of association between carbon dioxide and methyl diethanolamine at different temperature and amine wt% that was obtained in the first approach was used and volume of association and binary interaction between carbon dioxide and methyl diethanolamine were optimized. In both approaches, carbon dioxide has been considered as two association schemes: 1) as an association molecule with 3B and 4C association schemes, 2) as a non-association molecule. The results obtained in this work showed a good compatibility with the experimental data for this 3-component system. Comparison the results between this work and the Clegg-Pitzer and N-Wilson-NRF models reveals that the cubic plus association model leads to more convincing results than both of them. Furthermore, results obtained from the 4C association scheme for carbon dioxide in the cubic plus association equation of state shows a lesser error compared to 3B association scheme and to non-association scheme.

In the present research, the equilibrium data of ternary systems, carbon dioxide- toluene- naphthalene is determined by using a high-pressure apparatus. Mentioned data is measured between 298.15 K and 308.15 K and pressure at 9.6 to 75.6 bar. In each experiment, equilibrium solubilities of naphthalene in toluene decrease by increasing the pressure due to adding the carbon dioxide as the anti-solvent. Also, the obtained experimental data have correlated by the Soave-Redlich-Kwong equation of states along with Van der Waals 1 and 2 mixing rules.The adjustable parameters of mentioned models are obtained using the experimental data and reported along with average absolute relative deviation of each model. The results show that SRK equation of state with vdW2 mixing rule (AARD = 11.75 %) has less deviation than SRK-vdW1 (AARD =14.41 %) and optimum operational condition for production of fine particles (over than 90%) in the GAS process has been suggested.

In this research, dissolution of molybdenite through electro-oxidation of molybdenite concentrate in alkaline electrolyte solution was investigated. Effect of various parameters, including operating potential, liquid to solid ratio, NaCl concentration and distance between electrodes on the dissolution of molybdenite and the consumed electric energy within the electrochemical cell was studied. The results show that, dissolution of molybdenite was increased by increasing operating potential, liquid to solid ratio and NaCl concentration. The same was increased by increasing the distance between electrodes up to 10 mm, while for further distances the latter decreased. The energy consumption increased by increasing operating potential, liquid to solid ratio, and the distance between electrodes. The consumed energy also decreased by increasing NaCl concentration up to 100 g/L, while for further salt concentrations the latter increased. At optimum conditions including operating potential of 3 V, liquid to solid ratio of 200 mL/g, NaCl concentration of 100 g/L, distance between electrodes of 10 mm, and a period of 4 hours operation, the efficiency of molybdenum recovery and energy consumption were 70.41% and 5.56 kWh, respectively, per kilogram of molybdenite concentrate.

Vane plates are considered as one of the most efficient devices in industry which are widely used to eliminate liquid droplets from gas flows. In this study, the two-phase flow of gas-liquid between the wavy plates of a type of vane separator was simulated using Computational Fluid Dynamics (CFD) technique and influences of three independent factors of inlet gas velocity, vane spacing and vane angle on the separation efficiency were investigated. To model the liquid-gas flow, Eurelian-Lagrangian approach was applied and separator efficiency was evaluated within a velocity range of 3-8m/s while mass fraction of liquid droplets in the gas flow was 0.089. The liquid film breakup phenomenon was considered in these simulations. Having compared simulation results with experimental data, we realized that there was an average error about 0.9% in simulations. Regarding the simulation results, vane separation efficiency depends on inlet gas velocity and geometrical parameters of the vanes.

Poly-Gamma-glutamate, biopolymer polyamide is consisting of units glutamic acid, that due to biodegradability and non-toxicity property as a biological compound can be used in many fields such as medical and pharmaceutical, food, hydrogels, flocculants, moisture absorbers, thickener and drug carriers and anti-corrosion coatings. Therefore, have been done extensive studies to the over efficiency production of the biopolymer. That is why in this study was evaluated the effect of the concentration of nitrogen source as an important nutritional source on the pH and cell growth, then was studied in terms of how and through what mechanism the production of species flavobacterium gamma glutamate made an impact and Finally, in order to optimize the nitrogen source evaluated five different nitrogen source and sodium glutamate with the highest yields