فهرست مطالب zohreh saadati

In the current study, an in-depth examination was conducted to evaluate how the particle size of titanium dioxide (TiO2) will affect the mechanical, thermal, and morphological properties of the modified Pebax/TiO2 nanoparticle membrane. TiO2 nanoparticles were initially modified with amino silane and then incorporated into the nanocomposite Pebax/TiO2 membrane. The obtained membranes were characterized by FT-IR, SEM, TEM, TGA, and XRD to assess the effect of modification. The result of membrane performance evaluation indicated that the solubility of the gas molecules increased within the polymer matrix when an increase in CO2 permeability was observed. To test the performance of the nanocomposite membrane in the high-pressure separation process, the feed pressure was increased from 2 to 10 bar and the results demonstrated that the CO2/CH4 selectivity boosted from 16.05 to 97.74, respectively. Furthermore, when the surface of TiO2 nanoparticles was modified by amino silane and its concentration increased in the polymer matrix, the CO2 permeability of the nanocomposite membrane increased from 87.12 to 24.71 compared to that of the pure Pebax membrane. Experimental data were correlated with ANN (artificial neural network. The ANN of the model applied in this study includes the Levenberg-Marquardt algorithm, purelin or a linear transfer function at the output layer, and tansig or a tangent sigmoid transfer function in the hidden layer with 5 neurons.

The shale formation drilling often generates a wide range of problems if ordinary water-based muds are employed. Furthermore, the alteration of shale formation has complicated the development of adequate drilling fluids. The con trol of shale instability by the exchange of potassium cations with shale structure is well accepted in the drilling fluid industry. In the cases where seawater or brackish water is used as a base, the presence of Na+ and Cl- in the drilling fluid can disrupt the shale cation exchange process. In this study, KCl fluids with concentrations of 1 to 15 wt% were prepared and analyzed with linear swelling, capillary suction time, and dispersion experiments on shale inhibition property, and then NaCl was added to potassium fluids at different concentrations. The different result of mixed salt fluid and KCl fluids indicated that the presence of sodium chloride could affect the potassium yield in the drilling fluid. Moreover, the low concentration of NaCl/KCl showed better results for shale inhibition, although the increase in NaCl concentration caused high swelling and decreased KCl efficiency in drilling fluid. Ultimately, it was found that the addition of 1 – 5wt% NaCl to 3 – 5wt% KCl was preferable to stabilizing old shale formation. But to drill active and young shale formation, the use of KCl alone in the liquid was recommended.

Abstract Presence of toxic heavy metals like nickel in water resources is a major environmental problem in many communities.   In this study, to stimulate the removal of Ni (II) from aqueous solution by silica aerogel-activated carbon nanocomposite, the parameters affecting the adsorption process such as pH, amount of adsorbent, contact time, temperature and concentration were investigated and optimized. The results showed the maximum adsorption at pH= 5. The lower pH, the more H+ ion competing with the metal ion for adsorption sites. Kinetic studies indicated that the adsorption process followed the pseudo-second order kinetics. Moreover, the equilibrium data related to adsorption isotherms showed a superiority of the Langmuir isotherm compared to other models. Discussion and Calculation of thermodynamic factors, such as ΔG◦, ΔH◦ and ΔS◦, indicated that the adsorption process is spontaneous, endothermic and irreversible. The results showed that silica aerogel-activated carbon nanocomposite has been successfully employed for the removal of Ni (II) from aqueous solutions.

Some water and wastewater pollutants cannot be eliminated with traditional treatment methods. This has encouraged workers to focus on high performance and environmentally friendly methods for their removal. The main objective of this study was to evaluate the performance of MCM-48 in phenol removal from water. MCM-48 was synthesized and the effective parameters were evaluated. The results showed that maximum absorption of phenol in optimal conditions 0.3g adsorbent, time equals 30 minutes, pH =6, concentration in 2.5 mg / L at a temperature of 298 K and constant engine speed 300 rpm at about 88 percent. The thermodynamic parameters showed an adsorption process is spontaneous and exothermic. The Langmiur model fitted well the experimental data with a maximum adsorption capacity of 38.02.

An agricultural waste and eco-friendly biosorbent i.e. rice husk has been used as a cheap adsorbent for the removal of methylene blue dye from aqueous solutions. The physical properties of the developed adsorbent were characterized using FTIR. The study was realized using batch experiments. The effects of contact time, pH, initial dye concentration, biosorbent dose and temperature were investigated. The adsorption data were evaluated by Freundlich and Langmuir isotherm models. The adsorption isotherm is best fitted by the Freundlich model, while the adsorption kinetics is well described by the pseudo-secondorder model. Different thermodynamic parameters i.e., changes in standard free energy, enthalpy and entropy have also been evaluated and it has been found that the dye adsorption onto rice was a spontaneous, endothermic and physical reaction.

The interactions of β-lactoglobulin AB in the presence of cationic surfactants such as Cetyltrimethylammonium bromide and Cetyltrimethylammonium p-Toluenesulfonate have been investigated using a variety of experimental techniques such as conductivity, UV-Vis spectrophotometry and fluorimetry. The conductivity of surfactants aqueous solutions with β-lactoglobulin shows that the cmc of cationic surfactants decreases with increasing of counterion size. The results of UV-Vis and fluorescence studies show a red shift in wavelength and an increase in absorbance and intensity of the emission maximum of protein during the interactions of surfactants with β-lactoglobulin. The results of UV-Vis also show two distinct conformational changes at pHs 6.7 and 8.0 and the cooperative character of binding at pH 2.0. The results of fluorescence studies show that the binding strength of β-lactoglobulin / surfactant complex decreases with increasing of the pH.

An agricultural waste and eco-friendly biosorbent i.e. rice husk has been used as a cheap adsorbent for the removal of methylene blue dye from aqueous solutions. The physical properties of the developed adsorbent were characterized using FTIR. The study was realized using batch experiments. The effects of contact time, pH, initial dye concentration, biosorbent dose and temperature were investigated. The adsorption data were evaluated by Freundlich and Langmuir isotherm models. The adsorption isotherm is best fitted by the Freundlich model, while the adsorption kinetics is well described by the pseudo-secondorder model. Different thermodynamic parameters i.e., changes in standard free energy, enthalpy and entropy have also been evaluated and it has been found that the dye adsorption onto rice was a spontaneous, endothermic and physical reaction.

The interactions of β-lactoglobulin AB in the presence of cationic surfactants such as Cetyltrimethylammonium bromide and Cetyltrimethylammonium p-Toluenesulfonate have been investigated using a variety of experimental techniques such as conductivity, UV-Vis spectrophotometry and fluorimetry. The conductivity of surfactants aqueous solutions with β-lactoglobulin shows that the cmc of cationic surfactants decreases with increasing of counterion size. The results of UV-Vis and fluorescence studies show a red shift in wavelength and an increase in absorbance and intensity of the emission maximum of protein during the interactions of surfactants with β-lactoglobulin. The results of UV-Vis also show two distinct conformational changes at pHs 6.7 and 8.0 and the cooperative character of binding at pH 2.0. The results of fluorescence studies show that the binding strength of β-lactoglobulin / surfactant complex decreases with increasing of the pH.

Thermal denaturation of a-Lactalbumin in the absence and presence of various concentrations of sucrose,sorbitol, glucose and galactose as sugar osmolytes were measured by monitoring changes in the absorptions thatcarried out in a Lambd 35 UV-Vis double beam spectrophotometer at pH 6.0. These measurements gave valuesof T., (midpoint of denaturation), AH., (enthalpy change at T.), and ACp (constant-pressure heat capacitychange) under a given solvent condition. Using these values of AH., T., and AC, AGD° (Gibbs energy change),was determined at a given concentration of each sugar. It has been observed that each sugar stabilizes the a-Lactalbumin in terms of T,„ and AGD°. The temperature that corresponds to maximum protein stability, Ts, isincreased in the presence of these osmolytes. The same trend was also observed for TM, the temperaturecorresponding to zero enthalpy change of denaturation

Thermal denaturation of p-Iactoglobulin type B in the absence and pteNcno: of g arious concentrations oftrehalo5e, sucrose and sork toles sugar osmolytes and twlyols were nuyoured hy monitoring changes in theabsorption coefficients at pH 2.0. These measurements gave aliss, or I. mpdpDint of denaturation), Al-fis(enthalpy change at Ty). and ACp (consttun-pressure heal capaciit eh.iltgtii under a gisen solvent conditionUsing these valuer of Ali,, rs, and AC, , AG D° (Gibbs Dieu:, chantiet was determined at a givenconcentration of each sugar. Ii has been obsessed that each sugar glafili se. the 13-lac toglob B m ternsof 3. and AGna. The temperature that corresponds to rtmirntim proiv in Rahflits.. Is is increased G thepresence of these osmulytes. The same rend was also obsessed for fir,. the temperanirc corresponding tonun eat-haler change of denaturation.

Chemical denaturation and thermal denaturation of13-lactoglobulin A (f3 — lgA) in the absenceand presence of various concentrations sugar osmolytes and polyols were measured bymonitoring changes in the absorption coefficients at pH 2.0. It has been observed that AGD°(H20), (Gibbs free energy change in absence of denaturant at 25 °C) of f3-1gA in the presenceof 10% (w/v) Trehalose, Sucrose, Sorbitol and Mannitol is increased. We report that thefunctional dependence of AGD°, (Gibbs free energy change at 25 °C) of protein in the absenceand the presence of sugar osmolytes on denaturant concentration is linear. Trehalose is foundto induce remarkable stability of 13-1gA against chemical denaturation. The values of Tm(midpoint of denaturation), AHm (enthalpy change at Tm), and ACp (constant-pressure heatcapacity change) under a given solvent condition were measured. It has been observed thateach sugar stabilizes the protein in terms of Tm and AGD°.