نشریه شیمی و مهندسی شیمی ایران
سال سی و پنجم شماره 1 (پیاپی 79، بهار 1395)

Simultaneous presence of heavy metal and organic compound (like phenol and cadmium), is one of the most important environment pollutant source that there are in petrochemical industrial, plating and etc, that have adverse effects on environment and human health. Therefore, the purpose of this study is, photocatalytic removal of cadmium with UV/ZnO process in presence and absence of phenol and formate as hole scavenger from aqoues solution in batch system. First, design and construction of reactor was done. To the study on role of adsorption process, solution was equilibrium in dark for 30 minute. Then effect of various parameters was investigated in the presence of UV light. So optimum pH was obtained with chang solution pH and constant conditions. After clarifing optimum pH, the effect of nanoparticle dosage, concentration of cadmium, contact time and effect of presence and absence of phenol and formate was investigated. Although removal of cadmium increased with increase of pH, but to preservation of cadmium in the solution form, in experiment pH was 7. Removal efficiency increased with increase of contact time and optimum dosage was obtained equal to 2 g/L. Too photocatalytic removal efficiency was decreased with increase of initial cadmium concentration. Also the obtained results showed that presence of phenol and formate cause increase of cadmium removal efficiency. Generally the result of this study showed that studied methodology can be used as a effective method in photocatalytic removal of cadmium with UV/ZnO process in presence of phenol and formate as hole scavenger.

In the present study, the raw rice husk was used as adsorbent for removal of crude oil from aqueous solution. The sorbent was characterized by CHNS analyzer, ICP-OES spectroscopy, Fourier Transform InfraRed (FT-IR) and Scanning Electron Microscopy (SEM).The oil adsorption percent was determined by weighting method. The effect of various parameters including contact time, particle size, initial oil concentration, adsorbent dose on adsorption were investigated.
The results showed that the adsorption kinetics was rapid and the kinetics data for oil sorption were precisely described by the pseudo-second order model. The decrease of particle size of the raw rice hulls reduced the oil sorption percent from 50% to 30%. Also, the adsorption of crude oil on rice hull obeyed the Freundlich isotherm model.The highest adsorption percentage of crude oil on the raw rice hull at optimized conditions was about 55%.

Finding the perfect absorbent for the removal of a color with higher absorbent capacity and attract more colors, and determining the optimum conditions for the use of absorbent for textile factories and the environment is of particular importance. The purpose of this study was to evaluate and optimize the adsorption of Astrazon blue cationic dye from aqueous solution using sulfunated styrene-co-divinylbenzene resin. The variable amount of time, the adsorbent dosage and dye concentration were optimized by experimental design method. Numbers of 15 experiment was designed with Response Surface Methodology (RSM) and use the Box-Behnken design (Box-Behnken) with Design Expert 7.0.0 Trial software by three factors: time, adsorbent dosage and dye concentration in three levels (, 0, 1) with three- center points. Each experiment was done with a certain dose of adsorbent in 10 mL solution containing cationic dye and the dye adsorbed was measured.

In this research, sedimentation of magnesium hydroxide with high purity by Tachyhydrite was tested. For this aim Tachyhydrite solution and calcium hydroxide solution were mixed. This reaction involves the evolution of pH. At the end of experiment the slurry was filtered and washed with water and dried at 100°C. In order to increase filtration rate of Mg(OH)2 an agglomeration system by an anionic polyelectrolyte was applied. The product was then characterized by a complexometric titration to find the total calcium and magnesium content of sediment. Purity of magnesium hydroxide is important because of its use in preparation of magnesium oxide. Magnesium oxid should be high pure because it is used in production of refractories.

In the present study, modeling of nitrogen and methane separation in a spiral wound membrane module has been performed. For this purpose, some simplifications have been made which although simplified the model and eliminated unnecessary complexities, does not reduced the accuracy and made it as a very useful applicable model. For this purpose, an approximate modeling technique for spiral wound membranes in separating binary gas mixture is used for investigation of effects of increase membrane area and feed specifications (such as flow rate, concentration and pressure) on N2/CH4 separation. The results showed that based on the membrane selectivity, any changes in flow rate, concentration and pressure of feed and membrane surface can cause improvement or decrement in methane recovery and methane concentration in the product flow.On the other hand, it was also found that increase in the membrane surface area, improves methane recovery in the methane selective membranesand decreases in the nitrogen selective membranes. Moreover, by increasing the membrane surface area, methane concentration in product stream decreases while it increases for nitrogen selective membranes. Then, it is necessary to establish a balance between the amount of methane recovery and methane concentration in the product.

In this paper, three polymeric surfactants (PVA¡ P123 and PEG) were used for preparation of magnesium oxide with precipitation method. The prepared samples were evaluated by XRD¡ BET and SEM techniques. The results showed that the surfactant has a positive effect on the surface area and pore size of magnesium oxide. The magnesium oxide prepared by PVA has the highest surface area among the prepared samples. The catalytic results of 10%Ni catalysts supported on MgO prepared by different surfactants in dry reforming of methane revealed that all catalysts have a high catalytic activity and stability and the nickel catalyst supported onmagnesium oxide prepared with P123 has the highest activity in dry reforming of methane.

In this paper, the deactivation of Pd-Ag/Al2O3 catalyst was investigated in acetylene selective hydrogenation. Therefore, the commercial catalyst performance was used in Godinez kinetic model. The deactivation kinetic constant of catalyst was calculated by appropriate deactivation order. The activity of main and side reaction was evaluated during time on stream.
If first or second deactivation kinetic order was assumed, the activity lost was 90% and 1%, respectively. Since lower order was increased deactivation, so the second order deactivation model was proposed. As well the effect of temperature on the activity lost by using this model in acetylene selective hydrogenation was investigated.

Interest in research and development as well as utilization of Cellulose NanoFiber (CNF) has increased drastically over last decades. Therefore, surface chemical modification and improvement of CNF properties can open up new applications with giving new property while keeping its inherent properties. In this research, in order to enhance thermal stability of CNF cyanoethylation was carried out by acrylonitrile grafting at 60°C under alkaline condition. Degree of Substitution (DS) of cyanoethylated samples was calculated after determination of nitrogen content by Kjeldahl method. Moreover, the chemical structure of modified CNF was characterized with FT-IR spectroscopy and X-Ray Diffraction (XRD) pattern analyses. Thermal stability of modified CNF was then assessed by ThermoGravimetric Analysis (TGA) at three heating rate of 10ºC/min, 15ºC/min, and 20ºC/min under nitrogen atmosphere. Differential ThermoGravimetry (DTG) curves were plotted using TGA data and activation energies were calculated from experimental data. Results of nitrogen content measurements demonstrated DS=0.87 achievement. In addition, cyanoethylation of CNF was confirmed by FT-IR spectra analyses in comparison with control samples and detection of absorption band at 2250 cm-1 which is attributed to nitrile groups. Decrease in CNF crystalinity due to cyanoethylation was demonstrated by XRD analyses. Results of TGA also indicated high thermal stability of cyanoethylated CNF in comparison with unmodified CNF. Moreover, thermal decomposition of both untreated and cyanoethylated CNF occurred in one stage and increased with increasing heating rate. Also low activation energy was observed in cyanoethylated CNF than unmodified CNF. It seems that grafting of acrylonitrile to CNF can increase its utilization in special applications due to improving thermal stability and giving thermoplasticity because of playing role as internal plasticizer.

In this study heterogeneous cation exchange membranes based on PVC were prepared by using tetrahydrofuran as solvent and cation exchange resin powders. The membranes were fabricated by solution casting technique. At first, the effect of polymer binder sulfonation and its concentration in the casting solution on electrochemical properties of membranes was studied. Then, superior membrane was modified again by using of iron-nickel oxide nanoparticles.The obtained results showed that increase of sulfonated polymer’s concentration in membrane matrix caused to increase of membrane water content (from 29.4% to 35.1%) and ion exchange capacity (from 2.7 to 3.2). Moreover, prepared membranes exhibited suitable transport number and selectivity between 91%-93% and 85%-89% respectively. Ionic flux was increased initially by increase of sulfonated polymer concentration up to 80 %wt in membrane matrix and then decreased again by more increase in S-polymer content from 80 to 100 %wt. Membrane electrical resistance also was declined up to 27.6% by increase of S-polymer’s ratio in membrane matrix. Furthermore, using of iron-nickel oxide nanoparticles in membrane matrix caused to improvement of membrane electrochemical characteristics obviously. The modified nanocomposite membranes exhibited more appropriate separation performance compared to un-modified ones.The obtained results are useful for electro-membrane processes especially electrodialysis in water recovery and treatment.

The effect of three commercial types of titanium dioxide (TiO2) with primary particle sizes of 20 to 50 nm have been used for different sunscreens formulations. The efficiency of these sunscreens formulations, such as Sun Protection Factor (SPF), UVAPF and critical wavelength (λc) were tested. Oil/water creams with 5%, 10%, and 20% concentrations of each type of TiO2 were prepared, and SPF, UVAPF and λc were measured using both in vitro and in vivo methods. Because the samples have been aggregate and made the agglomerations, the milling and hemogenation methods have been used for decrease size of particles. In vitro analysis demonstrated that submicron-sized TiO2 cream had a lower SPF value than nanosized TiO2 formulations of the same concentration. In vivo experiments confirmed this result, and a strong correlation between in vitro and in vivo measurements was observed. Furthermore, the SPF values of nanosized TiO2 sunscreen were concentration-dependent in the range of 5% to 20%. Scanning electron microscopy results indicate that the higher SPF of nanosized TiO2 formulations may be due to the formation of multilayer agglomerates by small particles at nano-scales, leading to a reduced void space between particles and a more efficient barrier to protect skin from sunlight.

In this study, a thermodynamic model is presented for the study of the phase equilibria of clathrate hydrates of refrigerants namely Chlorodifluoromethane (R22), Trifluoromethane (R23), difluoromethane) R32), Pentafluoroethane (R125), 1,1,1,2-tetrafluoroethane (R134a), 1,1-difluoroethane (R152a), and carbon dioxide (R744). For the modeling of the vapor and liquid phases, the Peng-Robinson equation of state modified by Stryjek and Vera (PRSV2) and the Margules-type mixing rule were employed. To achieve more accurate results, binary interaction parameters are adjusted as a function of temperature. The model is based on equality of water fugacity in the liquid water and hydrate phases. Equation of Du and Guo has been used for the calculation of the Langmuir constant. Also, the parameters was fitted by Nedler–Mead non-linear regression method. The experimental and predicted values show good agreement. The average absolute deviation values of models for R22, R23, R32, R125, R134a, R152a, and R744 refrigerants hydrates are about 1.33%, 0.24%, 0.71%, 1.34%, 0.84%, 0.99%, and 0.97% respectively.

One of the effective factors on the efficiency of the flotation process, is bubble size distribution. Bubble size influences the bubble/particle collision, attachment and detachment probability. In this paper, size distribution of bubbles produced in a laboratory mechanical flotation cell, has been investigated by the direct image analysis method. In addition, effect of some important parameters such as frother concentration, pH value and temperature on bubbles size have been studied. In order to sample bubbles for imaging, bubble viewer with a viewing chamber was designed and made. Images were analyzed using Image J Ver. 1.44 software. To reduce number of bubbles in imaging zone and minimizing bubble overlap, the tube diameter was chosen small as much as possible so that quality and accuracy of image analysis were improved. In addition, by covering side walls of viewing chamber, light entrance from these walls was prevented and images quality was enhanced. Moreover, by photography field depth adjustment and also applying suitable lens, existing problems in previous studies such as bubble overlap and error induced by perspective were improved. To minimize bubble diameter standard deviation, 200 images per experiment were taken and some of them were randomly chosen analyzed. Study of frother effect on bubble size showed that with increase of frother concentration from 10 ppm to 60 ppm, Sauter diameter (d32) of bubbles decreased from 910 mm to 706 mm. with increasing pH from 4 to 10.4, in sync with increase of zeta potential absolute value, d32 of bubbles decreased from 1020 mm to 754 mm and bubble size distribution curve became similar to normal distribution. Furthermore, increase of temperature from 10 °C to 47 °C, resulted enlargement of Sauter diameter of bubbles from 611 mm to 830 mm.