Procedure for determining the number of thermal diffusion columns in square cascade for separation of Ne stable isotopes

The thermal diffusion column represents one method of separating stable isotopes.This method is advantageous for smallscale operations because of the simplicity of the apparatus and small inventory,especially in gas-phase operations.Consequently,it has attracted attention for its applicability in tritium and noble gas separation systems.In this study,the R cascade was used to design and determine the number of columns.A square cascade was adopted for the final design because of its flexibility,and calculations were performed to separate 20Ne and 22Ne isotopes.All the R cascades that enriched the Ne isotopes by more than 99%were investigated,the number of columns was determined,and the square cascade parameters were optimized using the specified columns.Additionally,a calculation code“RSQ_CASCADE”was developed.A unit separation factor of three was considered,and the number of studied stages ranged from 10 to 20.The results showed that the column separation power,relative total flow rate,and required number of columns were linearly related to the number of stages.The separation power and relative total flow decreased and the number of columns increased as the stage number increased.Therefore,a cascade of 85 columns is recommended to separate the stable Ne isotopes.These calculations yielded a 17-stage square cascade with five columns in each stage.By changing the stage cut,feed point,and cascade feed flow rate,the best parameters for the square cascade were determined according to the cascade and column separation powers.As the column separation power had a maximum value in cascade feed 50,it was selected for separating Ne isotopes.

Experimental mass transfer coefficients in a pilot plant multistage column extractor

The volumetric overall mass transfer coefficients in a multistage column have been measured using axial dispersion model for toluene–acetone–water system. The effect of operating parameters on the volumetric overall mass transfer coefficients has been investigated for both mass transfer directions. The results show that the mass transfer performance is strongly dependent on rotor speed and mass transfer direction, although only slightly dependent on phase flow rates. In addition, empirical correlations to predict the overall mass transfer coefficients have been developed. The proposed correlations based on dimensionless numbers can be considered as a useful tool for the possible scale up of the multistage column extractor.

Prediction of mass transfer coefficients in an asymmetric rotating disk contactor using effective diffusivity

Mass transfer characteristics have been investigated in a 113 mm diameter asymmetric rotating disk contactor of the pilot plant scale for two different liquid–liquid systems. The effects of operating parameters including rotor speed and continuous and dispersed phase velocities on the volumetric overall mass transfer coefficients are investigated. The results show that the mass transfer performance is strongly dependent on agitation rate and interfacial tension, but only slightly dependent on phase flow rates. In this study, effective diffusivity is used instead of molecular diffusivity in the Grober equation for estimation of dispersed phase overall mass transfer coefficient.The enhancement factor is determined experimentally and there from an empirical expression is derived for prediction of the enhancement factor as a function of Reynolds number. The predicted results compared to the experimental data show that the proposed correlation can efficiently predict the overall mass transfer coefficients in asymmetric rotating disk contactors.

Gamma-ray shielding study of light to heavyweight concretes using MCNP-4C code

In this work, linear and mass attenuation coefficients, half and tenth-value layers, effective atomic number and electron density of different types of concretes were determined at 316.51, 468.07, 511, 662, 1173 and 1332 keV using MCNP-4C code and Win XCom programs. The MCNP-4C and Win XCom results agreed well with each other, with differences of \±1.9%. The results agreed with available experimental data, too, with differences of \±6%.The MCNP-4C results showed better agreement with the experimental data than the Win XCom results. Also, it was found that the effective electron density of studied concretes varies in the range of(2.83–3.2) 9 10^(23)electron/g.

Preconcentration of rare earth elements from Iranian monazite ore by spiral separator using multi-response optimization method

The present work dealt with the preconcentration of rare earth elements in Saghand ore(Yazd province,Iran)which was achieved by Humphrey spiral using orthogonal optimization method after scrubbing the sample at 45%solid pulp density for 30 min.The pulp was diluted and was fed to a Humphrey spiral for upgrading.The process parameters considered were feed size,feed solids and feed rate,and Taguchi’s L9(34)orthogonal array(OA)was selected for optimization of the process.The results show that the feed rate and feed size were more significant than the other operation parameters of the process.It was also found that under optimal conditions,the concentrate grade of rare earth elements increased from2860 10 6to 6050 10 6and recovery reached to 58%.

Use of axial dispersion model for determination of Sherwood number and mass transfer coefficients in a perforated rotating disc contactor

The mass transfer process in a perforated rotating disk contactor(PRDC) using a toluene-acetone-water system was investigated.The volumetric overall mass transfer coefficients are calculated in a PRDC column.Both mass transfer directions are considered in experiments.The influences of operating variables containing agitation rate,dispersed and continuous phase flow rates and mass transfer in the extraction column are studied.According to obtained results,mass transfer is significantly dependent on agitation rate,while the dispersed and continuous phase flow rates have a minor effect on mass transfer in the extraction column.Furthermore,a novel empirical correlation is developed for prediction of overall continuous phase Sherwood number based on dispersed phase holdup,Reynolds number and mass transfer direction.There has been great agreement between experimental data and predicted values using a proposed correlation for all operating conditions.

Morphology and photoluminescence of BaMoO_4 micro-and nano-crystals synthesized by coprecipitation method

Barium molybdate（Ba Mo O4） micro- and nano-crystals were synthesized by the coprecipitation method. Utilizing the water as the solvent provides octahedron-like nanostructures. These nano-crystals were structurally characterized by X-ray diffraction, energy dispersive X-ray micro-analysis, Fourier transform infrared spectra. The size and shape were observed by scanning electron microscopy. The optical properties were studies by ultraviolet-visible diffuse reflectance spectroscopy and photoluminescence measurements at room temperature. The effects of temperature, solvent, surfactant and barium source were considered to obtain a controlled shape. It is found that the morphology, particle size and phase of the final products are extremely affected by these parameters.

Fault depth estimation using support vector classifier and features selection

Depth estimation of subsurface faults is one of the problems in gravity interpretation. We tried using the support vector classifier （SVC） method in the estimation. Using forward and nonlinear inverse techniques, detecting the depth of subsurface faults with related error is possible but it is necessary to have an initial guess for the depth and this initial guess usually comes from non-gravity data. We introduce SVC in this paper as one of the tools for estimating the depth of subsurface faults using gravity data. We can suppose that each subsurface fault depth is a class and that SVC is a classification algorithm. To better use the SVC algorithm, we select proper depth estimation features using a proper features selection （FS） algorithm. In this research, we produce a training set consisting of synthetic gravity profiles created by subsurface faults at different depths to train the SVC code to estimate the depth of real subsurface faults. Then we test our trained SVC code by a testing set consisting of other synthetic gravity profiles created by subsurface faults at different depths. We also tested our trained SVC code using real data.

Synthesis of Gd_2O_3 nanoparticles:using bulk Gd_2O_3 powders as precursor

Gd2O3nanoparticles were synthesized from the commercial bulk Gd2O3 powders via a simple electrochemical method. The synthesized powders were characterized by means of X-ray powder diffraction(XRD),scanning electron microscopy(SEM), transmission electron microscopy(TEM) and Fourier transform infrared(FTIR) spectroscopy. The effects of solution p H on the morphological features of the sample were studied. The strategy developed in this study offers significant advantages for the synthesis of Gd2O3 nanoparticles from the bulk Gd2O3 powders compared with the conventional routes. From SEM observations, the size of the Gd2O3 nanoparticles is estimated to be significantly smaller than70 nm.

Coupling system application in photocatalytic degradation of methylorange by TiO_2, TiO_2/SiO_2 and TiO_2/SiO_2/Ag

Three different photocatalysts including TiO2, TiO2/SiO2 and TiO2/SiO2/Ag were synthesized via sol–gel growth method, in which colloidal silica was used as Si source, titanium tetra iso-propoxide (TTiP) as titanium source, Ag+ as dopant ion and hydroxypropyl cellulose (HPC) as dispersant. The purpose was to study the enhancement of photocatalytic activity of TiO2 by deposition on SiO2 colloids and also doping with Ag ion. The catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FT-IR) and Brunauer–Emmett–Teller (BET) methods. It is confirmed that the major phase in all catalysts is anatase. Photocatalytic activity was studied in various conditions for degradation of methylorange (as a model pollutant) to evaluate the effect of some parameters on degradation efficiency. Studying the degradation process in various pH values reveals that the degradation is more efficient in acidic solution than alkaline condition. Coupling the photocatalytic process with some fields called electro-photochemical (EP), magnetic-photochemical (MP) and ultrasonic-photochemical (UP) was studied at two pH values which were compared with photochemical (P) alone. It is concluded that in most cases, the EP is the best coupled system and has the maximum efficiency. Liquid chromatography–mass spectrometry (LC–MS) analysis was used to check the complete decomposition of methylorange at the end of process.

Facile synthesis, morphology and structure of Dy_2O_3 nanoparticles through electrochemical precipitation

The aim of this research was to introduce a new, facile and simple method for synthesis of Dy203 nanostructures at room temperature. For the first time, galvanostatic electrodeposition was used to synthesize Dy203 particles, and the influence of the current density on the structure and morphology of the product was studied. The samples were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM） and Brunauer-Emmett-Teller （BET）. The results show that the current density has little effect on the chemical composi- tion but great effect on the structure and morphology of the samples. The average size of the particles decreases as the applied current density increases. The grain size of as- prepared samples decreases from 500 to 70 nm when the current density increases from 0.5 to 6.0 mA.cm-a. To obtain oxide product, the as-prepared samples were heat- treated at 1,000 ℃. The results show that the heat-treated samples have smaller particles. The XRD results show that the similar patterns are observed in the samples synthesized at different current densities, and the only difference from the JCPDS card is the ratio of peak intensities. With the increase in the current density, a decrease in the current efficiency is observed.

Adsorptive separation of La(Ⅲ)from aqueous solution via the synthesized[Zn(bim)_(2)(bdc)]_(n) metal-organic framework

Lanthanum is one of the rare earth metals which due to specific chemio-physical properties,has wide applications in different industries.In this research,the ability of the synthesized metal-organic framework(MOF),[Zn(bim)_(2)(bdc)]_(n)(ZBB) for the removal of lanthanum ions from the aqueous stream was investigated in the batch and column processes.The synthesized MOF was characterized by using scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET),Fourier transform infrared spectroscopy(FTIR) and thermogravimetric analysis(TGA).The effect of pH on lanthanum ions adsorption was evaluated in the range from 1 to 7.Moreover,isothermal,kinetic,and thermodynamic parameters for adsorption of La(Ⅲ) ions onto the synthesized MOF were evaluated.The adsorption capacity of lanthanum ions onto the synthesized MOF was calculated to be about 130 mg/g.Thermodynamic studies demonstrate the endothermic and chemical nature of lanthanum adsorption,while kinetic studies suggest the pseudo-first-order of reaction.In column mode,the effect of solution flow rate passing through the fixed-bed was studied.Experimental data confirm that increasing the bed flow rate causes a decrease in the adsorption capacity of lanthanum ions on the synthesized MOF.

Kinetics of gadolinium extraction with D2EHPA and Cyanex301 using single drop column

The extraction kinetics of Gd（III） from the nitric acid medium using bis（2,4,4-trimethylpentyl） dithio- phosphinic acid （Cyanex301） and 2-ethylhexyl phosphoric acid （D2EHPA） in kerosene solution were measured by the single drop technique. The influences of hydrogen ion concentration, gadolinium ion concentration, extractant concentration, column height, and nozzle diameter on the extraction rate were investigated. The forward rate equations for the gadolinium extraction with D2EHPA and Cyanex301 were obtained. Based on the experimental results, the forward extraction rate constant was calculated. With the increase of D2EHPA or Cyanex301 concentration, the drop rising diameter and the value of interfacial tension decrease in the studied system, which shows that D2EHPA or Cyanex301 has interfacial activity as a kind of surfactant. Also, the droplet diameter and interfacial tension decrease with the increase of aqueous solution acidity. The experimental results show that the D2EHPA extractant provides faster extraction rate in comparison with Cyanex301 extractant, and it would be useful in industrial continuous extraction process.

Conversion of CO into CO_(2) by high active and stable PdNi nanoparticles supported on a metal-organic framework

The solubility of Pd(NO_(3))_(2) in water is moderate whereas it is completely soluble in diluted HNO_(3) solution. Pd/MIL-101(Cr) and Pd/MIL-101-NH_(2)(Cr) were synthesized by aqueous solution of Pd(NO_(3))_(2) and Pd(NO_(3))_(2) solution in dilute HNO_(3) and used for CO oxidation reaction. The catalysts synthesized with Pd(NO_(3))_(2) solution in dilute HNO_(3) showed lower activity. The aqueous solution of Pd(NO_(3))_(2) was used for synthesis of mono-metal Ni, Pd and bimetallic PdNi nanoparticles with various molar ratios supported on MOF. Pd_(70)Ni_(30)/MIL-101(Cr) catalyst showed higher activity than monometallic counterparts and Pd+ Ni physical mixture due to the strong synergistic effect of PdNi nanoparticles, high distribution of PdNi nanoparticles, and lower dissociation and desorption barriers. Comparison of the catalysts synthesized by MIL-101(Cr) and MIL-101-NH_(2)(Cr) as the supports of metals showed that Pd/MIL-101-NH_(2)(Cr) outperforms Pd/MIL-101-(Cr) because of the higher electron density of Pd resulting from the electron donor ability of the NH_(2) functional group. However, the same activities were observed for Pd_(70)Ni_(30)/MIL-101(Cr) and Pd_(70)Ni_(30)/MIL-101-NH_(2)(Cr), which is due to a less uniform distribution of Pd nanoparticles in Pd_(70)Ni_(30)/MIL-101-NH_(2)(Cr) originated from amorphization of MIL-101-NH_(2)(Cr) structure during the reduction process. In contrast, Pd_(70)Ni_(30)/MIL-101(Cr) revealed the stable structure and activity during reduction and CO oxidation for a long time.