EXTRACTION KINETICS OF YTTRIUM WITH PURIFIED CYANEX 923 FROM NITRATE MEDIUM

Mass transfer and extraction kinetics of yttrium with the purified Cyanex 923 in n-heptane from nitrate medium have been investigated by using a constant interfacial cell with laminar flow at 298K. The interfacial adsorption properties of purified Cyanex 923-heptane-0.20mol/L (H, Na)NO3 were studied at 298K. The experimental results show that the mass transfer is controlled by diffusion and the chemical reactions are carried out in the interfacial zone. The extraction rates of yttrium were measured at different chemical compositions by varying ionic strength, pH values and the purified Cyanex 923 concentrations. The initial extraction rate equations were obtained.

Extraction Kinetics of Lanthanum with Purified Cyanex 923 from Nitrate Medium

Solvent extraction kinetics of lanthanum with purified Cyanex 923 in heptane from nitrate medium was investigated by using a constant interfacial cell with laminar flow at 303 K. The effects of stirring speed, temperature and specific interface on the extraction rate were studied. The experimental results showed that the extraction apparent activation energy was 32.0 kJ\5mol -1 and the extraction process was controlled by both chemical reaction and diffusion. The extraction rates were measured at different chemical compositions by varying ionic strength, pH value and the concentration of purified Cyanex 923. The initial extraction rate equation was obtained.

KINETICS OF COPPER EXTRACTION BY N530-HEPTANE

The activity coefficients of all the components in H_2SO_4-CuSO_4 solution were calculated by using Pitzer's equation.Six Pitzer's mixing parameters μ and were evaluted.The change of the activity and concentration of the ions during extraction was measured by drop weight method.The interfacial excesses of all the components were calculated from the interfacial tension equation which is expressed in terms of activities of every components.Results show that H^+ and Cu^(2+) are positively adsorpted by CuR_2,(HR)_2 ,SO_4^(2-) and HSO_4^- are negatively adsorpted on the interface.

EXTRACTION KINETICS,SYNERGISTIC EFFECTS AND INTERFACIAL CHEMISTRY FOR D_2 EHPA MPA-Fe^(3+) MIXED EXTRACTION SYSTEM

The thermodynamics of micella formation,interfacial characteristics,synergistic effects and interfacial kinetics for synergistic extraction system D_2 EHPA-MPA-Fe^(3+) have been studied.It was found that D_2EHPA in the mixed system strongly exhibits the effect on the micella formation thermodynamics and interracial characteristics of MPA.Some ther- modynamic parameters for constants of micelles formation(K_m).free energies of micelles formation(ΔG_m)and critical micella concentrations(CMC)were obtained.The inter- facial adsorption behaviour of D_2EHPA is opposite to that of MPA.The emulsification for single MPA and the mixed system was discussed.The synergistic effects were found in this mixed extraction system.It is proved that the process of the Fe^(3+) extraction for non-mixed extraction system is controlled by chemical reaction and the controlling reaction occurs at the interface.

KINETICS OF YTTERBIUM ION EXTRACTION BY CA-12 AT THE LIQUID-LIQUID INTERFACE

The mass-transfer kinetics of ytterbium between aqueous solutions and heptane solutions of CA- 12 and CA-12-HEHEHP have been studied by using a constant interfacial area cell with laminar flow. The results have been interpreted according to a series of reversible interfacial reactions. In this work, it has been discovered that HEHEHP can increase the rate of ytterbium extraction by CA-12.

Extraction kinetics of phenol with N, N-di (1-methyl-heptyl)acetamide-kerosene using hollow fiber membrane extractor

Extraction kinetics of phenol with N,N-di(1-methyl-heptyl) acetamide-kerosene using hollow fiber membrane extractor has been studied. The rate regularities and kinetic types of forward and backward extraction were obtained respectively by determining the forward and backward extraction rate under various experimental conditions. The mass transfer mechanism was discussed. Both the forward and backward extraction of phenol might be controlled by diffusion processes, and the diffusion resistance for both forward and backward extraction mainly exists in aqueous phase. In addition, ways to optimize the extraction process of phenol were discussed as well.

KINETIC STUDY ON THE EXTRACTION OF PALLADIUM(Ⅱ) WITH BIS(2-ETHYLHEXYL)SULFIDE

The effects of concentration, temperature, stirring rate and specific interfacial area on the extraction of Pd (Ⅱ) with bis(2--ethylhexyl) sulfide (DEHS) were studied by the use of a constant interracial area cell. The results support an interracial chemical reaction regime.

Extraction Kinetics of Rare Earth Elements with sec-Octyl-phenoxy Acetic Acid

The kinetics of RE (La, Gd, Er, Yb and Y) extraction with sec octylphenoxy acetic acid was investigated using a constant interfacial area cell with laminar flow at 303 K. The natures of the extracted complexes have some effect on the extraction rate which is controlled by the reaction rate of M(III) and extractant molecules at two phase interface for Er(III), Yb(III) and Y(III), by a mixed chemical reaction diffusion for Gd(III) and a diffusion for La(III). The extractant molecules tend to adsorb at the interface. So an interfacial extraction reaction model was derived.

Reaction condition optimization and kinetic investigation of roasting zinc oxide ore using (NH_4)_2SO_4

An orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore using（NH_4）_2SO_4. The optimized reaction conditions are defined as an（NH_4）_2SO_4/zinc molar ratio of 1.4：1, a roasting temperature of 440°C, and a thermostatic time of 60 min. The molar ratio of（NH_4）_2SO_4/zinc is the most predominant factor and the roasting temperature is the second significant factor that governs the zinc extraction. Thermogravimetric-differential thermal analysis was used for（NH_4）_2SO_4 and zinc mixed in a molar ratio of 1.4：1 at the heating rates of 5, 10, 15, and 20 K·min-1. Two strong endothermic peaks indicate that the complex chemical reactions occur at approximately 290°C and 400°C. XRD analysis was employed to examine the transformations of mineral phases during roasting process. Kinetic parameters, including reaction apparent activation energy, reaction order, and frequency factor, were calculated by the Doyle-Ozawa and Kissinger methods. Corresponding to the two endothermic peaks, the kinetic equations were obtained.

Extraction kinetics and kinetic separation of La(Ⅲ),Gd(Ⅲ),Ho(Ⅲ) and Lu(Ⅲ) from chloride medium by HEHEHP

Acco rding to the tetrad-effect,14 elements of lanthanides can be divided into four groups.In our previous study,a new approach was proposed for the kinetic separation of four rare earth ions La(Ⅲ),Gd(Ⅲ),Ho(Ⅲ) and Lu(Ⅲ) coming from four groups.In that study,four rare-earth ions were kinetically separated from their coexisting mixed aqueous solutions,by performing liquid-column elution using the aqueous solution containing four lanthanide rare-earth ions as the stationary phase and the dispersed organic oil droplets containing HEHEHP(2-ethyl hexyl phosphonic acid mono 2-ethyl hexyl ester) extractant as the mobile phase.The study of extraction kinetics is very important for understanding the kinetic separation of rare earth ions,which was carried out in this paper.The extraction kinetics of La(Ⅲ),Gd(Ⅲ),Ho(Ⅲ) and Lu(Ⅲ) by HEHEHP diluted in heptane were investigated using single drop method.The different parameters affecting the extraction rate such as column length,specific interfacial area,rare earth ion concentration,extractant concentration,hydrogen ion concentration and temperature were separately studied and the rate equations are deduced.It is first order with respect to rare earth ion and HEHEHP concentrations,and negative first order with respect to hydrogen ion concentrations.The rate constants at 293.15 K are 10-6.23,10-5.73,10-5.58 and 10-5.43,respectively.The experimental results demonstrate that the extraction rate of La(Ⅲ), Gd(Ⅲ),Ho(Ⅲ) or Lu(Ⅲ) is diffusion-controlled,and the extraction reaction takes place at the interface rather than in the bulk phase.The extraction model was proposed.Besides,the kinetic separation of rare earth ions by HEHEHP oil drops was discussed.

Effect of ultrasound power on extraction kinetic model,and physicochemical and structural characteristics of collagen from chicken lung

The effects of ultrasound power on extraction kinetic model,and physicochemical and structural characteristics of collagen from chicken lung were studied.Ultrasound power caused a significant increase in extraction rate and equilibrium concentration,with the maximum extraction yield(31.25%)at 150 W.The experimental data were consistent with the predicted ones in this empirical equation,in which the percentage error differences was 0.026–4.159%.Besides,ultrasound treatment did not affect their triple-helical structure.The thermal stability of pepsin-soluble collagen by ultrasound pretreatment(UPSC)was higher,due to the higher imino acid content(20.76%).UPSC also exhibited better solubility and fibril forming capacity.Overall,the kinetic model of UPSC from chicken lung could serve the purpose of obtaining collagen,which displayed a potential alternative source to mammal collagens for application in food,biomaterials and biomedical fields.

Kinetic studies on the solvent extraction of uranium(VI) from phosphoric acid solution with HDEHP using laser-induced optical fiber fluorimetry

The laser-induced optical fiber fluorimetry has been used for the first time to analyse the concentration of uranium(VI) in the kinetic studies on the extraction of uranium(VI) between 0.5 mol/L H_3PO_4 solution and HDEHP-cyclohexane system with Lewis cell. The effects of stirring speed, temper- ature and concentration of uranium(VI) and HDEHP on the rate of extraction were examined. These data show that the extraction rate of uranium(VI) in this system is controlled by the chemical reaction process at the interface. The rate equations and the rate constants of the forward and reverse ex- tractions were obtained. The mechanism of the extraction has been discussed.