جستجوی مقالات مرتبط با کلیدواژه "استخراج حلالی" در نشریات گروه "فیزیک"

This research investigates and optimizes the parameters of solvent extraction processes using thorium leach solutions from Chahghaz ore with D2EHPA. The effective parameters in the solvent extraction process were evaluated through experimental design to maximize thorium extraction and minimize iron extraction. Under optimum conditions—pH 0.6, extraction time of 2 minutes, 16% solvent concentration, and an organic-to-aqueous phase ratio of 1:2—thorium and iron recoveries were 99.47% and 9.60%, respectively. For the optimization of the stripping process, 89.75% thorium and 0.6% iron were recovered in 3.34 minutes with an organic-to-aqueous phase ratio of 2:1 and a sulfuric acid concentration of 3.9M.

In this study, the separation of yellow cake impurities was investigated by solvent extraction (SX) method using Aliquat 336. The effects of contact time, type and concentration of extractant, type and pH of buffer and diluent type on the extraction rate of impurities from the aqueous phase were studied. Impurity separation experiments were done by solvent extraction method from the simulated solution. The optimal time for the contact of two phases to achieve the maximum amount of extraction of impurities compared to uranium was found to be 6 minutes. Aliquot 336 extractant had a better performance for the separation of impurities than N-benzoyl-N-phenylhydroxyl amine (BPHA) and N, N-dimethoxy phenyl formamidine (DMF). The optimal concentration for the extractant was 0.4 M and chloroform had the best performance among the diluents. The use of acetic acid-sodium acetate buffer with a pH of 3.6 led to the greatest removal of impurities. Also, the McCabe Thiele diagram showed that two extraction steps are needed to remove molybdenum impurity from the yellow cake sample. Therefore, it can be said that in the optimal conditions of the process parameters and with two stages of extraction, 94% of uranium remained in the aqueous phase and the amount of impurities was reduced below the permissible limit

Due to the limited uranium reserves, the abundance of thorium compared to it, not being used in nuclear proliferation, and other advantages of thorium fuels over uranium fuels, the development of the thorium fuel cycle in various countries, including Iran, is considered. In this research, the separation and recovery processes of thorium from a real acidic leach liquor solution with a concentration of 500 mg/L thorium on a laboratory scale to produce thorium oxide precipitate were evaluated. The operating parameters affecting the extraction, stripping, and chemical precipitation processes of thorium include the type of extractant (acidic, basic, and neutral), the concentration of the extractant (0.05-1 M), aqueous phase acidity (0.032-6.92), equilibrium time (5-60 min), type and concentration of stripper (1-7 M) and precipitating agent were studied by the univariate method in each section. According to the experimental results, Di(2-ethylhexyl) phosphoric acid with a concentration of 1 M as extractant, aqueous phase acidity equal to 0.1, equilibrium time 60 min, sulfuric acid with a concentration of 5 M as a stripper, and ammonia as a precipitating agent were selected. Recovery of thorium from a real acidic leach liquor solution under obtained conditions resulted in the production of thorium oxide precipitate with a purity of 66%.

The extraction and concentration of rare earths from leach liquor of apatite concentrate of central Iran were investigated using combined precipitation and solvent extraction methods. Precipitation was carried out to remove undesirable ions and solvent extraction method using tri-n-butyl-phosphate (TBP) as an extractant was employed to separate and concentrate rare earth elements. The XRD studies demonstrated that fluro-apatite, ancrite and calcite are the comprising minerals in the examined mica (apatite) and fluro-apatite is the predominant mineral. The amount of rare earth element-oxides including Y, Ce, La, Pr and Nd were determined by means of X-ray florescence (XRF) analysis. The other chemical composition of apatite consists of: SiO2, CaO, Fe2O3 and P2O5. First, acid leaching operation was carried out by using nitric acid. The analytical investigation of the obtained leach liquor indicated that interfering ions include: Fe(II), Mg(II), Ca(II), S(IV), P(V) and F(I). The precipitation studies confirmed that the process was rapid and highly efficient to remove the interfering ions without removing rare earth elements. The effect of different variables such as extractant concentration, nitric acide concentration, temperature, contact time and Vorg./Vaq. were investigated and the optimum conditions for separation of lanthanides by TBP were determined. Selective stripping of lanthanides from the loaded organic phase were studied using nitric acid. The separation of rare earths by TBP was observed to be significant and more than 90 percent of rare earth elements were extracted. The thermodynamic functions of lanthanides extraction process have been calculated.

The extractive separation of thorium, uranium, iron, titanium and lanthanides, represented by lanthanum, yttrium and cerium, has been investigated by Cyanex272 into the synthetic nitrate solutions. The concentration of each studied element in the synthetic solution was 10-4 M. It was found that the extraction increases in the order of La(III)<Ce(III)<Y(III)<Fe(III)<Th(IV)<U(VI)<Ti(IV). Thorium was optimally separated utilizing 0.5 M nitric acid solution. The slope analysis method showed that thorium was extracted as Th(OH)2(NO3)A.HA. Also, the effects of complexing agent, acid type and acid concentration on the stripping of thorium, uranium, lanthanum and iron from the loaded organic phase were studied by Taguchi method. The optimum conditions for the selective stripping of thorium were observed when 0.5 M sulfuric acid and 2.7´10-4 M EDTA were used. The thermodynamic functions have been calculated.

Zirconium and hafnium are the two most important elements in the nuclear industries. Zirconium is used in fuel rods due to its low neutron absorption cross section. On the contrary, hafnium has a very high neutron absorption cross section, therefore it must be separated from zirconium. The extractive separation of zirconium and hafnium have been investigated using Taguchi method. The separartion parameters were acid type (Sulfuric, Nitric, Hydrochloric) and their concentrations (10-2, 1, 5M) and extractant type (D2EHPA, Cyanex 301, Cyanex 302). The optimum conditions were determined as 5M nitric acid in addition with 5×10-3 M Cyanex 302 in the kerosene. Under these conditions, the zirconium the extraction percent and the separation factor were 99.5% and 8.7, respectively. For detailed investigation from the achieved results by Taguchi method, the effects of different parameters such as agitation time, nitric acid concentration, extractant concentration, sodium nitrate concentration and diluent type were considered.

In this research, separation of fluoride and uranyl ions from high content nitrate and fluoride solution, by γ-Alumina in moving and fixed bed methods, has been studied. In this investigation, the effect of some principal parameters such as, alumina weight, its particle size, and pH on the efficiency of separation of these ions from uranium solution, has been optimized. In the moving bed process, in fact, for decreasing pH, the best and economical condition for uranium extraction by solvent extraction process with TBP has been made available, and therefore it leads to save 800m3 HNO3 as a good advantage. In addition, in the fixed bed process, at an optimum pH, the concentration of uranyl and fluoride ions in the final raffinate decreased for uranium in a range of 50 ppb to 1.3 mg/L, and 170 ppb for fluoride. The effect of adsorption parameters on desorption of these ions was investigated and optimized by sodium carbonate solution. Uranium desorption from the column by sulfuric and nitric acid and sodium carbonate solution was carried out easily, and by sulfuric and sodium carbonate solution 99% recovery was obtained.