Kinetics of cerium(Ⅳ) and fluoride extraction from sulfuric solutions using bifunctional ionic liquid extractant(Bif-ILE)[A336][P204]

The extraction kinetics of Ce（Ⅳ） and Ce（Ⅳ）-F^- mixture systems from sulfuric solutions to n-heptane solution containing Bif-ILE[A336][P204]（[trialkylmethylammonium][di-2-ethylhewanxylphosphinate]） with a constant interfacial area cell with laminar flow were studied,just to elucidate the extraction mechanism and the mass transfer models.The data were analyzed in terms of pseudo-first-order constants.The effects of stirring speed,specific interfacial area and temperature on the extraction rate in both systems were discussed,suggesting that the extractions were mixed bulk phases-interfacial control process.Supported by the experimental data,the corresponding rate equations for Ce（Ⅳ） extraction system and Ce（Ⅳ）-F^- mixture extraction system were obtained.The experimental results indicated the rate-controlling step.The kinetics model was deduced from the rate-controlling step and consistent with the rate equation.

Kinetics of cobalt(Ⅱ) extraction from sulfate aqueous solution by sodium salt of di-decylphosphinic acid (DDPA)

Kinetics of Co（II） extraction from sulfate aqueous solution by the sodium salt of di-decylphosphinic acid （Na-DDPA） was studied using a modified Lewis cell to disclose the mechanism of extraction. Parameters affecting the extraction rate, such as stirring speed, temperature, interfacial area, Na-DDPA concentration and Co（II） concentration, were investigated, respectively. The effect of diffusion resistance on extraction rate was negligible when the stirring operation was conducted in a plateau region of 95-110 r/min. Extraction rate increased with the increase in the temperature or specific interfacial area. The activation energy E was calculated to be 32.75 kJ/mol. These suggested that rate controlling mechanism of Co（II） extraction by Na-DDPA was chemical reaction regime and the rate-determining step of Co（II） extraction was chemical reaction at the interface. The initial extraction rate also increased with the increase in the concentrations of Na-DDPA and Co（II）. The extraction rate equation and mechanism of Co（II） extraction by Na-DDPA were proposed.

Kinetic mechanism of copper extraction from methylchlorosilane slurry residue using hydrogen peroxide as oxidant

Copper was extracted from methylchlorosilane slurry residue by a direct hydrogen peroxide leaching method.A number of experimental parameters were analyzed to determine the extraction efficiency of copper.The extraction efficiency of copper reached 98.5%under the optimal leaching conditions,such as the hydrogen peroxide concentration of 1.875 mol·L^(-1),the leaching temperature of 323 K,the liquid–solid ratio of 20 ml·g^(-1),and the stirring speed of 300 r·min^(-1).The leaching kinetics of the copper extraction process was then described by the shrinking core model.There were two stages.The first stage was controlled by chemical reactions,while the second stage was controlled by interface transfer and product layer diffusion.The activation energy and kinetic control equations were determined,as well as an explanation of the leaching mechanism of copper extraction based on kinetic analysis and materials characterization.Copper resources can be recovered from the methylchlorosilane slurry residue efficiently and inexpensively with the methods used in this study.

Kinetics of Selective Hydrogenation of PAHs from FCC Slurry Extract over Ni-W/γ-Al_(2)O_(3) Catalyst

The selective hydrogenation of polycyclic aromatic hydrocarbons(PAHs)from fluid catalytic cracking(FCC)slurry extract was conducted in a batch reactor over aγ-Al_(2)O_(3)-supported bimetallic Ni-W catalyst.For the Ni-W/γ-Al_(2)O_(3) catalyst,the experiment run was divided into three processes according to the reaction conditions used:(1)the absence of hydrogenation as both temperature and pressure increased;(2)the desulfurization of FCC slurry extract under a fixed pressure as the temperature increased;and(3)the selective hydrogenation of PAHs when both pressure and temperature remained constant.The hydrogen consumption could be accurately calculated from the Redlich–Kwong equation of state.The results for the removal of PAHs with hydrogenation displayed an excellent fit to the first-order kinetics.The apparent activation energy was determined to be 20.80 kJ/mol.

Kinetics of forward extraction of Ti(IV) from H_2SO_4 medium by P_(507) in kerosene using the single drop technique

The kinetics of forward extraction of Ti（IV） from H2SO4 medium by P507 in kerosene has been investigated using the single drop technique.In the low concentration region of Ti（IV）,the rate of forward extraction at 298 K can be represented by F（kmol·m-2·s-1）=10-5.07 [TiO 2 ＋ ][H＋]-1 [NaHA 2 ]（o）·Analysis of the rate expression reveals that the rate determining step is（TiO）（i）2＋ ＋（HA 2）（i）-[TiO（HA2）]（i）＋.The values of Ea,H±,S±,and G±298 are calculated to be 22 kJ·mol-1,25 kJ·mol-1,-218 J·mol-1·K-1,and 25 kJ·mol-1,respectively.The experimental negative S± values indicate that the reaction step occurs via SN2 mechanism.

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 in Chloride Medium by Bifunctional Ionic Liquid [A336][CA-12] Using a Constant Interfacial Cell with Laminar Flow

The extraction kinetics of La(III) from aqueous chloride solutions into n-heptane solutions of bifunctional ionic liquid extractant [A336][CA-12](tricaprylmethylammonium sec-octylphenoxy acetic acid) was investigated using a constant interfacial cell with laminar flow. The effects of stirring speed, temperature and specific interfacial area on the extraction rate were examined. The results indicate that mass transfer kinetics of La(III) is a mixed-controlled process influenced by interfacial reaction. On the basis of mass transfer kinetic results in the extraction of La(III) by [A336][CA-12], the extraction rate equation of La(III) is proposed in terms of pseudo-firstorder constants, which is supported by the measured thermodynamic equations. The mass-transfer kinetic model deduced from the rate controlling step is adequate to interpret the experimental data qualitatively.

Kinetics and mechanisms of solvent extraction and separation of La(Ⅲ) and Ni(Ⅱ) with DEHPA in petrofin

The kinetics of extractive separation of La(Ⅲ) and Ni(Ⅱ) from nitrate medium in the presence of lactic acid (HLac) using di-2-ethylhexyl phosphoric acid (DEHPA) diluted in petrofin was investigated using a cell with constant interfacial area and continuous stirring. The effects of stirring speed, interfacial area, pH, HLac concentration, extractant concentration, concentrations of metal ions and temperature on the extraction rate were examined. Results suggested that the extraction regime is diffusion-controlled. The reaction which occurred at the interface was found to be the rate-determining step. The extraction rates of both metal ions are found to be independent of pH. The extraction rates of La(Ⅲ) and Ni(Ⅱ) are first-order dependent with respect to lactic acid and metal ions (La(Ⅲ) and Ni(Ⅱ)) concentrations. The extraction rate of La(Ⅲ) is first-order dependent on DEHPA concentration and for Ni(Ⅱ), it varies to the power of 1.5. The separation of La(Ⅲ) and Ni(Ⅱ) from nitrate solution is possible at low interfacial area and low stirring speed.

Kinetics of uranium extraction from coffinite——A comparison with other common uranium minerals

A synthetic coffinite was hydrothermally prepared and characterized before conducting a series of acid sulfate leach tests under conditions of relevance to uranium extraction.The results were then compared with similar studies on synthetic versions of the related U4+minerals uraninite(UO2)and brannerite(UTi2O6)to identify and differentiate the rate and U extraction among these important uranium minerals.Tests examining the influence of residence time on uranium dissolution from synthetic coffinite,uraninite and brannerite showed that under similar experimental conditions,complete dissolution of uranium from coffinite was obtained between 36 and 48 h.The activation energy for this reaction was calculated to be 38.4 kJ/mol.This represented a significantly slower rate of dissolution than that indicated for uraninite which dissolved in 3 h(Ea=15.2 kJ/mol).The synthetic brannerite was leached at a much slower rate than the coffinite and reached a maximum dissolution of^18%U in 144 h(Ea=42-84 kJ/mol).The clear differentiation in rates and U extraction among the three minerals is consistent with previous literatures which suggest that in terms of leachability,uraninite>coffinite>brannerite.It is expected that the presence of impurities in natural coffinites would further inhibit leachability.

Mechanism and kinetics of iron extraction from high silica boehmite−kaolinite bauxite by hydrochloric acid leaching

The chemical and mineral compositions of bauxite recovered from the Severoonezhsk Bauxite Mine(Arkhangelsk region,Russia)were studied by XRD,ICP-OES,TG/DSC,SEM,TEM,and Mössbauer spectroscopy.The iron-containing minerals of the bauxites were found to comprise alumogoethite(α-Fe_(1−x)Al_(x)OOH),alumohematite(α-(Fe_(1−x)Al_(x))_(2)O_(3)),alumoakaganeite(β-Fe_(1−x)Al_(x)O(OH,Cl)),and chromite(FeCr_(2)O_(4)).The efficiency of Fe extraction from the bauxite by HCl leaching was 82.5%at 100℃,HCl concentration of 10%,solid/liquid ratio of 1:10,and the process duration of 60 min,with aluminum loss from the bauxites below 4.5%of the total Al contents in the bauxite.Analysis of the kinetics of the iron leaching process proved diffusion to be the limiting stage of the process at 90−100℃.Bauxite residue after leaching presented traces of α-Fe_(1−x)Al_(x)OOH and β-Fe_(1−x)Al_(x)O(OH,Cl),and most of the iron content was in the FeCr_(2)O_(4).In bauxite residue after HCl leaching,in addition to iron oxide,the contents of chromium and calcium oxides significantly decreased.The iron chloride liquor after leaching contained the rare earth elements(REE)of 6.8 mg/L Sc,4.1 mg/L Ce and 2.3 mg/L Ga.

Kinetics of Forward Extraction of Boric Acid from Salt Lake Brine by2-Ethyl-1,3-hexanediol in Toluene Using Single Drop Technique

The kinetics of forward extraction of boric acid from salt lake brine by 2-ethyl-1,3-hexanediol in toluene was investigated using the single drop technique. The factors affecting the extraction rate include interfacial area between aqueous phase and organic phase, initial concentration of boric acid in aqueous phase, initial concentration of 2-ethyl-1,3-hexanediol in organic phase, and extraction temperature. The experimental results show that the extraction rate increases with the increase of the initial concentration of boric acid and2-ethyl-1,3-hexanediol, interfacial area of two phases, and temperature. With the temperature-dependence study, it is showed that the extraction is a diffusion-controlled process. The kinetic equation is presented for pH 1.0 in the aqueous phase and temperature of 318 K.

Reaction mechanism and kinetics of pressurized pyrolysis of Chinese oil shale in the presence of water

A study of reaction mechanisms and chemical kinetics of pressurized pyrolysis of Chinese Liushuhe oil shale in the presence of water were conducted using an autoclave for simulating and modeling in-situ underground thermal degradation.It was found that the oil shale was first pyrolyzed to form pyrobitumen,shale oil,shale gas and residue,then the pyrobitumen was further pyrolyzed to form more shale oil,shale gas,and residue.It means that there are two consecutive and parallel reactions.With increasing temperature,the pyrobitumen yield,as intermediate,first reached a maximum,then decreased to approximately zero.The kinetics results show that both these reactions are first order.The activation energy of pyrobitumen formation from oil shale is lower than that of shale oil formation from pyrobitumen.

Kinetics and mechanism of Re(Ⅶ) extraction and separation from Mo(Ⅵ) with trialkyl amine

The extraction kinetics of rhenium(Ⅶ) or molybdenum(Ⅵ) with trialkyl amine (N235, R3N, R=C8–C10) dissolved in heptane were investigated by constant interfacial cell with laminar flow, which aimed to identify the extraction regime, reaction zone and rate equations. The influence of stirring speed, temperature, specific interfacial area, extraction concentration and chlorine concentration on the extraction of both metals was studied. It is concluded that the extractions of Re(Ⅶ) and Mo(Ⅵ) both take place at the liquid-liquid interface, while the extraction regimes are chemically-controlled for rhenium and mixed controlled for molybdenum, respectively. The extraction rate equations and the rate-determining step were obtained under the experimental conditions, and the extraction rate constant of Re(Ⅶ) or Mo(Ⅵ) with N235 was calculated. These obtained kinetics parameters are different between Re(Ⅶ) and Mo(Ⅵ), which provides better possibilities for Re(Ⅶ) and Mo(Ⅵ) separations at proper conditions.

Co-extraction of valuable metals and kinetics analysis in chlorination process of low-grade nickel-copper sulfide ore

To efficiently co-extract Ni and Cu from low-grade nickel-copper sulfide ore,chlorination roasting with NH;Cl followed by a water leaching process was investigated.The results show that 98.4%Ni and 98.5%Cu can be synchronously extracted when the ore particle size is 75-80μm,the roasting time is 2 h,the mass ratio of NH;Cl to ore is 1.6:1 and the roasting temperature is 550°C.The evolution behavior of various minerals was elucidated using X-ray diffraction(XRD)coupled with scanning electron microscopy(SEM).The kinetics of the chlorination process based on the differential thermal and thermogravimetric analysis(DTA-TG)data was analyzed by Kissinger method and Flynn-Wall-Ozawa(FWO)method.The chlorination process of low-grade nickel-copper sulfide ore mainly contains two stages:the decomposition of NH;Cl and the chlorination of ore.The maximum apparent activation energies(Ea)at two stages are determined to be 114.8 and 144.6 kJ/mol,respectively.The condensed product of exhaust gas is determined to be ammonium chloride,which can be recycled as the reactant again,making the process economic and clean.

Kinetics of Reactive Extraction of Nd from Nd2O3 with TBP-HNO3 Complex in Supercritical Carbon Dioxide

The process based on supercritical fluid extraction for reprocessing of the spent nuclear fuel has some remarkable advantages over the plutonium-uranium extraction(PUREX) process.Especially,it can minimize the generation of secondary waste.Dynamic reactive extraction of neodymium oxide(Nd2O3) in supercritical carbon dioxide(SC-CO2) containing tri-n-butyl phosphate-nitric acid(TBP-HNO3) complex was investigated.Temperature showed a positive effect on the extraction efficiency,while pressure showed a negative effect when the unsaturated TBP-HNO3 complex was employed for the dynamic reactive extraction of Nd2O3 in SC-CO2.Both temperature and pressure effects indicated that the kinetic process of the reactive extraction was controlled by the chemical reaction.A kinetic model was proposed to describe the extraction process.

A novel constant interfacial area cell for determining the extraction kinetics of Er(Ⅲ) from chloride medium

A novel constant interfacial area cell(NCIAC),by spatially separating the agitation from liquid flow circulation of organic and aqueous two phases,was suggested to obtain detailed kinetic data for Er(Ⅲ) extraction from chloride medium by 2-ethyl-hexyl-phosphonic acid mono-(2-ethylhexyl) ester(EHEHPA).Different from the traditional Lewis cell and the constant interfacial area cell with laminar flow,the concentrations of Er(Ⅲ) in organic and aqueous two phases were uniform,and the stability of the interfacial area between the two phases could be controlled effectively.Therefore,the special requirements for the design of agitators in the traditional Lewis cell and the constant interfacial area cell for minimizing the influence of diffusion resistance could be avoided.Experimental results indicated that the extraction kinetics was mainly affected by the aqueous flow rate,interfacial area between organic and aqueous two phases,and the aqueous p H values.An extraction kinetic equation was suggested based on the experimental data.

Extraction kinetics of zinc by new extractant in ammoniacal system

The controlling step and the extraction reaction rate equation of zinc extraction from Zn（II）-NH3 solution by using a newly synthesized organic compound, 2-acetyl-3-oxo-dithiobutyric acid-myristyl ester as the zinc extractant, were clarified. The effects of agitation speed, specific interfacial area, temperature, extractant concentration and Zn ion concentration on the extraction rate are studied in constant interfacial area cell. The results show that the extraction rate depends on interfacial chemical reaction and diffusion by using this new extraetant to extract zinc, and the apparent activation energy of this extraction reaction is measured as 28.2 kJ/mol, which demonstrates that the extraction reaction is controlled by the mixed-controlled reaction rate. The apparent reaction orders a and b are measured as 1 and 0.38, and the constant k0 is 138.70. So, when extraction conditions are controlled as [HR]=20%-50%, T=0-30℃, N=120-177 r/min and S=72.6-127.5 m-1, the solvent extraction reaction rate can be depicted as v/（mol . m-2 . s-1 ） = 138.7. exp（ - 28 206/8.314T ）. [Zn 2＋ ]r ·[HR ]o0.38.

Extraction and stripping kinetics of copper(Ⅱ)by N902 using single drop technique

The kinetics of extraction and stripping of copper （Ⅱ） was investigated by the single drop technique with a new extractant N902 （a derivative of the salicylal-doxime） and the rate equations of extraction and stripping were derived, respectively. The apparent activation energies of extraction and stripping were estimated to be 20.14 kJ/mol and 30.0 k J/mol.

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 Extraction of <i>β</i>-Carotene from Tray Dried Carrots by Using Supercritical Fluid Extraction Technique

β-carotene acts as an antioxidant and is receiving growing interest due to its ability as protecting agent against heart diseases, cancer and strengthening effect on red blood cells. The main aim of this work was to study the kinetics of the supercritical fluid extraction of β-carotene from tray dried carrots at 40℃, 50℃ and 55℃ and 30, 35 and 40 MPa at SC-CO2 flow rate of 2.0 L/min for extraction time of up to 6 h. It was observed that the concentration of β-carotene in the extract increased with pressure, temperature and extraction time. The results indicated that yield was found to be maximum at 45℃ and 35 MPa at 2 L/min SC-CO2 flow rate. Concentration of β-carotene in the extract increased with SC-CO2 flow rate. Weibull distribution model described adequately the kinetics of extraction of β-carotene from carrots.