نشریه شیمی و مهندسی شیمی ایران
سال سی و چهارم شماره 3 (پیاپی 77، پاییز 1394)

In recent years, nano Zero valent iron (nZVI) have been used to remediate from polluted groundwater. However the application of nZVI has limitations such as particles agglomeration and filtration of nano particles. This research has been conducted to enhance the usability of nZVI by supporting with diatomite during synthesis. The characterization for nZVI particle and dolomite supported (D-nZVI) was performed using XRD, SEM/EDAX, TEM, and BET-N2.nZVI, D-nZVI and pure diatomite are used as adsorbents and nickel solution were applied as heavy metal adsorbents to remove the aqueous Ni2 ions and varying factors including adsorbent dosage, solution pH, contact time, and initial metal concentration have been investigated. The Langmuir and Freundlich adsorption isotherm models over a wide initial concentration dosages were used in order to determine the adsorbents adsorption capacity that results showed that D-nZVI has a higher adsorption capacity, and Also fitting the data using these models showed that the adsorption of all adsorbents are in good agreement with the Langmuir model. The adsorption capacity of the above adsorbents were found, 66.67, 166.67, 13.16 mg/g, respectively .The removal kinetics were modeled by pseudo first-order and pseudo second-order models and the results showed that removal of Ni2 by all adsorbents could be better expressed by pseudo second-order kinetics.

In this research, a V-SBA-16 catalyst was prepared using SBA-16 nanoporous material as a support and vanadium complex via a reflux method (V-SBA-16). The catalyst was characterized using N2 adsorption–desorption isotherms, X-Ray Diffraction (XRD), Ultraviolet-visible spectroscopy, and transmission electron microscopy. Characterization results showed that the ordered nanoporous structure of the support was retained during the catalyst preparation and did not collapse. The efficiency of catalyst was evaluated for direct oxidation of benzene to phenol at different reaction temperatures (25, 60 and 90 °C). The higher yield and selectivity toward phenol were obtained of 16% and 60%, respectively, at 60 °C.

Thesluggish of Oxygen Reduction Reaction (ORR) kinetics at the cathode account the majority of the voltage drop in H2-PEMFCs. As many limiting processes take place in the reaction layer, it is important to model this layer. In this work, a two-dimensional steady state model for a PEM fuel cell cathode is described. All the components in the cathode such as the gas manifold, diffusion layer, micro-porous layer and the catalyst layer were modeled. Concentrations of gaseous components, liquid water saturation in the cathode catalyst layer and ionomer local potential calculated to solve the equations in MATLAB. After comparing the results of the model and experimental data, the design parameters include platinum loading, catalyst layer thickness and ionomer weight fraction was chosen to achieve maximum current density. The optimal values were 0.9 mg.cm-2, 15 µm and 55% for platinum loading, catalyst layer thickness and ionomer weight fraction at high voltage and 0.5 mg.cm-2, 30 µm and 45% at low voltage respectively.

In this experimental study, molecular diffusion coefficient of benzoic acid in aqueous base γ-Al2O3-Water nanofluids was measured by using very simple and inexpensive method. Nanofluids consisted of γ-Al2O3 nanoparticles which were suspended in deionized water as based fluid. Nanoparticles diameters were from 10 nm to 20 nm. The volumes ratios of nanoparticles have been used in experiments were 0.025% 0.05%, 0.1%, 0.2%, 0.4% and 0.8%. All of the experiments were performed at constant temperature in 20 oC. The results revealed that addition of γ-Al2O3 nanoparticles to the based fluid did not have a significant effect on Benzoic acid diffusion in nanofluids.

Biological uptake of heavy metals is a very effective process for removing these pollutants from aqueous solutions is considered.Algae cell wall composition of cellulose and other materials such as agar, alginate and the metal ions play a key role in biosorption. Algae are of particular importance due to their low cost. Mechanisms are involved in the uptake of metals by bacteria is very complex and depends on physicochemical reactions of metal ions in solution, and so are the locations of cellular uptake. Microorganisms and algae contribute to the cycle of inorganic substances in nature.In this study the biological uptake of nickel by red algae Gracilaria, brown algae Cystoseira, Fucus and Gram-positive bacteria Bacillus, was studied.Parameters such as metal concentrations, pH, amount of algae, kinetic, and isotherms were studied in this experiment. The maximum rates of metal uptake by algae Gracilaria, Cystoseira and Bacillus at pH=6 and Fucus on the pH is about 5. The maximum nickel sorption was attained about for Fucus, Gracilaria, Cystoseira, and Bacillus, 0.94, 0.68, 0.34 and 0.65 mg/L respectively. This study has shown nickel (II) uptakes, equilibrium time of about 400,350,300 and 120 minutes for, Gracilaria, Cystoseira, Fucus and Bacillus, respectively, and the adsorption equilibrium date was well described by Langmuir equation.

In this research, fungus Phanerochaete chrysosporium has been used to effectively reduce the gold adsorption ability of carbonaceous matter on one hand, and decompose metal sulfides on the other, to ultimately enhance the gold extraction. Two ranks of coal (ordinary and anthracite) were used as substitutes to investigate the ability of fungus to reduce the gold adsorption by carbonaceous matter. The results showed that the ability of anthracite coal in gold adsorbing is 5 times more than ability of ordinary one. Phanerochaete chrysosporium reduced the ability of anthracite by over 85% for a 21 days culturing period under processing in PBD (Potato Dextrose Broth) medium and 95% for the same period in MWB (Millet and Wheat Bran) medium. Phanerochaete chrysosporium has also ability to oxidize the sulfide existing in refractory gold ores. The pyrite initial weight decreased by 35% for pH equal 7 and 30% for pH equal 4 in 21 days
of processing. Pretreatment was performed for Zarshouran refractory gold ore with different percentage of orpiment and gold. After a 14 days of processing, the amount of gold extraction by cyanidation of samples (1) (-2210 µm fraction containing less orpiment than natural samples),(2) (similar to natural samples from the amount of orpiment point of view), and (3) (� µm fraction containing enriched over 85% orpiment) increased to 30%, 25% and 1% respectively and sulfide mineral existing in samples (1) and (2) both decreased by over 50%. According to the results, Phanerochaete chrysosporium is a microorganism with high potential for oxidizing the sulfide minerals and neutralizing the carbonaceous matter existing in refractory gold ore simultaneously and totally, it has a high potential for increasing the gold recovery in cyanidation of refractory gold ore.

The flotation behavior of pyrolusite and calcite was investigated using oleic acid as an anionic collector and dodecylamine as a cationic collector. The results showed that using oleic acid the maximum flotation recovery of pyrolusite occurs at pH=9 due to the chemisorptions of oleate ions, while in the cationic flotation the physisorption of dodecylamine results in a maxima at pH=8. It was found that in the anionic flotation, copper sulfate (CuSO4.5H2O) acts as pyrolusite activator and calcite depressant agent. The best results were obtained using 1000 g/t copper sulfate in the presence of 10-4 M oleic acid at pH=8. At these conditions the flotation recovery of pyrolusite and calcite are 83.6% and 38%, respectively. In the cationic flotation, sodium carbonate and calcium chloride depress the calcite flotation significantly. Using 10-4 M sodium carbonate without a significant decrease in pyrolusite floatability the calcite flotation recovery reduces to 13.7 % at a pH of 7.5. At this pH, the use of 5×10-4 M calcium chloride with a slight decrease in pyrolusite floatability decreases the calcite flotation recovery from 57.2% to 10.8%. Thus, the cationic flotation using sodium carbonate as a depressant agent for calcite is suggested for separation of pyrolusite from calcite.

Drilling mud plays an important role in drilling operations which affects both the quality of drilled well and efficiency of drilling operations. In this study, the effect of polyacrylamide and Barite/polyacrylamide nanocomposite additives has been investigated on the properties of drilling mud. The nanocomposite was produced through the solution polymerization method. The produced nanocomposite was added to the water based drilling mud (350 mL water with 10 g of bentonite) and its main properties including viscosity, fluid loss (invasion), and mud cake thickness were examined. Results showed that, adding nanocomposite caused reduction of fluid loss, decrease in mud cake thickness and increase in the viscosity of drilling fluid.

In this paper the effect of nanofluids in a thermosiphon reboiler has been studied and simulate a thermosiphon available in the university of Manchester with the HTRI software package. It is revealed that how the performance and subcool length were influenced by using nanofluid applications. The result of this simulation shows the heat transfer coefficient increases by the increase of nanofluid concentration which leads to a decrease in heat transfer area and smaller equipment in its design. The subcool length is also decreased.

The use of desalination is one of the ways to deal with the water crisis. Humidification-Dehumidification ( HD) of air process is one of the small scale desalination method witch is in the special attention nowadays. In this paper a new design for hybrid domestic solar water heater/ desalination unit is presented. That designed to supply drinking water and hot water for a domestic user in remote and desert areas. After reviewing various combinations of these two devices and choosing the best option, the hybrid system was constructed in Iranian Research and Development Center for Chemical Industries (IRDCI). The necessary tests were carried out and various parameters which are affecting the performance of unit such as water flow rate of the condenser, water temperature interval and solar radiation were tested. By using four solar collector with 8 m2 surface area, this device be able to produce about 20 liters of fresh water and at least 250 liters of hot water. Since output of the brackish water is used as hot water, it reduces the waste water in desalination unit that may be result in zero discharge of waste water in some days. So in addition to providing heating by the use of solar energy, water saving will be accessible for the consumer.