جستجوی مقالات مرتبط با کلیدواژه « کبالت » در نشریات گروه « فیزیک »

In this research, extraction of cobalt ions from non-aqueous medium was carried using Aliquat336 extractant. The effect of different parameters on the non-aqueous extraction process including ethylene glycol concentration, extractant concentration, hydrochloric acid concentration and cobalt ions concentration in aqueous solution was investigated using the experimental design approach. According to the desirability of one and the maximum extraction efficiency of cobalt ions, the optimal conditions include volume percentage of Aliquat336 (19.2%), cobalt concentration (899.4 ppm), volume percentage of ethylene glycol (65.3%) and hydrochloric acid concentration (7.81 M) were obtained. The validity of the data was observed with minimal error between the predicted data (94.82%) and the experimental data (99.36%).

Graphene oxide/cobalt nanocomposite was synthesized using the electrooxidation method and its structural and magnetic properties were specified. The effect of the produced nanocomposite on the rheological properties of drilling fluids containing bentonite and natural gum was investigated. The nanocomposite was characterized using XRD, FT-IR, SEM and VSM. XRD results confirmed the formation of graphene oxide/cobalt nanocomposite. The SEM images show the scaly shape of cobalt nanoparticles substituted on the graphene oxide sheets. Based on VSM results, the saturation magnetization, remance magnetization and coercive field were determined to be 167.04 emu/g, 9.94 emu/g, and 142.5 Oe, respectively. In order to investigate the effect of graphene oxide/cobalt nanocomposite on the rheological properties of two types of fluids containing bentonite and natural gum, 0.1, 0.3, and 0.5 gr of nanocomposite were added to drilling fluids and their rheological properties were measured using an eight-speed viscometer at three temperatures of 23oC, 50oC and 70oC. Graphene oxide/cobalt nanocomposite in the bentonite samples increases the apparent viscosity, plastic viscosity, yield point, and gel strength up to 108 cp, 17 cp, 165 lb/100ft2, and 170 lb/100ft2, respectively, and decreases these parameters in the samples containing natural gum down to 70 cp, 32 cp, 42 lb/100ft2, and 5 lb/100ft2, respectively.

The safety assessment of Anarak site as the only center for the disposal of radioactive waste is of particular importance in order to maintain human health and the environment. Distribution coefficients of radioactive materials in the soils of the area under study is one of the influential parameters in the safety assessment calculations. Therefore, in this study, the distribution coefficient of cobalt in the alluvial soil of Anarak waste was determined by the batch method and two parameters of concentration and soil to solution ratio were studied. Linear adsorption isotherms, Friendlich and Langmuir were also analyzed to determine the adsorption behavior of cobalt in Anarak soil. The average value of cobalt distribution coefficient in the mentioned soil was calculated equal to 247.18 mL / g. The adsorption behavior of cobalt in Anarak soil followed the Langmuir adsorption isotherm with a positive and significant correlation. The maximum amount of cobalt uptake was determined as 0.029 mg / g soil. The results of the distribution coefficient obtained in this study are lower than the most of the values ​​presented in the other previous researches, which can be related to the soil texture (sandy loam) and the other soil characteristics.

Electronic properties for bcc Fe and hcp Co in bulk state and also Fe-Co alloy were calculated by quantum calculation based on density functional theory and pseudopotential method. Combination of Wannier function and Berry phase theory was used for calculation of anomalous Hall conductivity in above structures. It was seen that split of band by the spin orbit interaction، lying on the Fermi level، has a major role in Berry curvature. Acquired results agree with experimental ones and thus it seems that conductivity in bulk state is intrinsic.

In this study, the production of labeled vitamin B12 with one strain of actinomycet in a novel synthetic medium by batch fermentation method was investigated. After releasing vitamin B12 from microbial cells, the solution containing cobalamin analogues was fixed on amberlite XAD-4 exchanger and eluted by various solutions. Vitamin B12 in the collected fractions were measured by HPLC method and also in order to confirm the existence of cobalamin compounds in the samples, TLC technique was used. In the optimal conditions, production of vitamin B12 by this microorganism was 1456µg/l. The best recoveries of vitamin B12 from the column were obtained when the column was eluted by ethanol followed by acetone. The Rf values for cyanocobalamin and methylcobalamin, produced by this microorganism were the same as the standard values of Rf. The desorption of labeled vitamine B12 was carried out by different eluants, including acetone, ethanol (absolute), ethanol 25% and deionized water. The activity of labeled vitamin B12 was 8.55, 6.90, 0.79, 5.75 Bq/ml, respectively. Therefore, the total specific activity of 21.99Bq/ml was obtained for labeled vitamin B12.

Trace amounts of cobalt-57 were separated from nickel and extracted into isopherone in the presence of thiocyanate as a complexing agent. The effect of various parameters on the separation yield was investigated. These include: concentration of the complexing agent, aqua and organic phases volume ratio and acidity of aqua phase. The extracted cobalt-57 was backextracted into concentrated hydrochloric acid and the effects of hydrochloric acid concentration and volume on backextraction yield were investigated. 4% (W/V) ammonium thiocyanate solution, pH=1.5-2 and lower organic to aqua volume ratio gives the highest separation yield. 99.57% backextraction yield was achieved for cobalt-57 through 5 steps of washing with 5 N HCl.