Extraction of scandium from red mud by modified activated carbon and kinetics study

Activated carbon （AC） was modified by tri-butyl phosphate （TBP） for selectively extracting scandium from red mud and characterized by BET （Brunauer-Emmett-Teller） surface area. The modified AC had a preferential adsorption to scandium. The influences of adsorbent dos- age, adsorption temperature, and time on adsorption capacity and selectivity to scandium were examined. An optimum adsorbent dosage （-6.25 g/L）, adsorption temperature （308 K）, and adsorption time （40 min） were figured out. A pseudo-second-order kinetics model was employed for describing the adsorption process of scandium.

Trace Determination of Scandium Using Adsorption Voltammetry of Mix-Polynuclear Complex of Scandium-Calcium-Alizarin Red S at Carbon Paste Electrode

A novel method was described for the determination of ultra trace amount of scandium based on the cathodic adsorptive voltammetry of the mix-polynuclear complex of scandium-calcium-alizarin red S at a carbon paste electrode (CPE). The 2nd-order derivative linear scan voltammograms of the adsorbed complex were recorded by model JP-303 polarographic analyzer from 0.0 to -1.0 V (vs. SCE). The experimental conditions of the working procedure were optimized. The results show that the complex can be adsorbed on the surface of the CPE, yielding one peak at -0.61 V, corresponding to the reduction of the alizarin red S in the mix-polynuclear complex at the electrode. The detection limit of Sc^(3+) is 1.0×10^(-10) mol·L^(-1) for 3 min of accumulation time. The procedure was successfully applied to the determination of trace amount of scandium in the sample ores.

Microstructures and Properties of Al-Zn-Mg-Cu-Zr Alloys with Minor Scandium

The microstructures of Al-Zn-Mg-Cu-Zr al- loys with minor Sc were studied by using optical microscope（OM）, scanning electron microscope （SEM） and transmission electron microscope（TEM）. The tensile mechanical properties and electric conductivity of the studied alloys under different treatment conditions were tested. The results show that adding minor Sc can greatly fines the grain size of the Al-Zn-Mg-Cu-Zr alloy ingots and obviously improves the tensile properties and electric conductivity of the alloys. The strengthening mechanism is considered as fine grain strengthening, sub-structure strengthening and dispersion strengthening by Al3 （Sc, Zr）.

A facile synthesis of 2,3-dihydro-2-aryl-4(1H)-quinazolinones catalyzed by scandium(Ⅲ) triflate

2,3-Dihydro-2-aryl-4（1H）-quinazolinones were prepared in good yields via condensation of o-aminobenzamide with aldehydes promoted by a catalytic amount of Sc（OTf）3 under mild conditions.

Scandium recovery from raffinate copper leach solution as potential new source with ion exchange method

Raffinate copper leach solution of the Iran Sarcheshmeh copper complex has up to 3 mg/L scandium(Sc),which is significantly better than many existing sources,making it a possible source for the recovery of Sc using the ion exchange method.Visual Minteq software was employed to ascertain the ionic species likely to be formed under operational conditions in the mine and for selecting the suitable ion exchange resin.The cationic resin thus chosen was employed statically with ions-bearing synthesized solutions and statically/dynamically for actual copper mining raffinate solution.Room temperature and pH of 1.5 showed the highest Sc adsorption.The dynamic tests established the full saturation of the resin at 450 BV of the raffinate solution flow.Using sodium carbonate for elution,desorption of Sc,Y and Ce from the resin during static elution tests at constant duration was higher than that of Fe,Al and Cu.The results from the dynamic tests followed similar trends for the priority and the extent of the elution process.Desorption results from specimens of dynamic tests show a 60:1 concentration ratio leading to a 186 mg/L Sc-rich solution.

Removal of impurities from scandium solutions by ion exchange

A process of removing impurities,such as Fe,Zr,Ti,Al,Si,from scandium solution by ion exchange was proposed.Various resins’selectivity was studied in scandium chloride solution.The results indicated that D851resin had high selectivity of Sc at low acidity,and high selectivity of Zr at high acidity;D370resin had high selectivity of Fe and Si in high acidity.A new technical process of removing impurities from scandium chloride solution was proposed,which includes D370resin adsorbing Fe in high acidity,D851resin adsorbing Zr in medium acidity and D851resin adsorbing Sc at low acidity.Flow experimental results show that removal rates of Al,Ca,Fe,Zr,Ti and Si,were100%,99.6%,100%,100%,99.5%and100%respectively.

Enhanced extraction of scandium and inhibiting of iron from acid leaching solution of red mud by D2EHPA and sodium chloride

D2EHPA(P204),tri-butyl-phosphate(TBP)and sodium chloride(NaCl)were attractive for selective extraction of scandium from acid leaching solution of red mud.The extraction parameters of P204 concentration(X_(P204)),NaCl concentration(C_(NaCl)),pH value,reaction time,stirring speed and O/A were investigated to extract scandium and separate iron from the acid leaching solution.The extraction mechanism was analyzed by Fourier transform infrared spectroscopy(FT-IR)and thermodynamic theory.The single-stage extraction efficiency of scandium,iron andβ(Sc/Fe)were 99.1%,9.4%and 1061.2,respectively,with C_(NaCl) of 75 g/L and XP204 of 0.75 at solution pH value of 1.2 and stirring speed of 200 r/min for 6 min,in which a good separation effect of scandium and iron was obtained.The vibration absorption peak Sc─O was contributed to the extraction of scandium with P204.The complex[FeCln]^(3−n) existed in the solution with adding NaCl into the acid leaching solution.The value of n was higher and the valence state of the complex[FeCln]^(3−n) was lower with an increase of chloride concentration,which restricts the extraction efficiency of iron with P204.The extraction of three stages in the counter-current simulation experiments was carried out according to the McCabe-Thiele diagram.Gibbs free energy change(ΔG)of−5.93 kJ/mol,enthalpy change(ΔH)of 23.45 kJ/mol and entropy change(ΔH)of 98.54 J/(mol·K)were obtained in the solvent extraction proces,which indicate that the extraction reaction is easily spontaneous and endothermic and a proper increase of temperature is conducive to the extraction of scandium.

Scandium recovery from ion-adsorption rare earth concentrate with HEHEHP as extractant

An excellent extraction selectivity towards Sc over other REEs in 4 mol/L HCl solution was achieved with the separation factor βSc/REEs over 8000 by 2-ethylhexyl phosphoric acid mono 2-ethylhexyl ester(HEHEHP)and the extraction equilibrium can be obtained within 20 min.The extracted Sc can be stripped using 5 mol/L NaOH solution as eluent at 363 K with the stripping rate of 92.1%obtained.The extraction mechanism was clearly elucidated by slope analysis,saturation extraction,IR,and NMR analysis.It was revealed that the extraction of Sc in 4 mol/L HCl solution is still dominated by cation exchange process between P-O-H and Sc,and coordination process between P=O and Sc,with 6 molecules of extractant as dimer participating in the process.Finally,a flowsheet for the recovery of Sc from ion-adsorption rare earth elements(REEs)concentrate was proposed and proved in lab-scale experiment.

Efects of minor amounts of scandium on microstructure and mechanical properties of ZA27 alloy

The influences of minor amounts of scandium on the microstructure and mechanical properties of as-cast ZA27 alloy have been experimentally investigated. The experimental results show that as far as the Sc addition is individually concerned, the refinement result of the as-cast ZA27 alloy with 0.5wt.%Sc addition is comparatively better. After alloying with minor amounts of Sc, the coarse dendrites of the ZA27 alloy are refined and transformed into the uniform and small equiaxed grain microstructure; also the eutectics among the grain boundaries become finer. The test results of mechanical properties show that the tensile strength and hardness of the as-cast ZA27 alloy containing 0.5wt.%Sc approach 495 MPa and 120.2 HB, increase by 28.5% and 33.1%, respectively, compared with those of the ZA27 alloy with no addition of Sc element, while the elongation of the alloy is improved to 7.6% from 2.7%. The SEM, EDAX and XRD analyses show that in the ZA27 alloy, the trace element Sc combines with AI to form the square AI3Sc phase particles, which serve as heterogeneous nuclei, facilitating the refinement of the microstructure and the improvement of the mechanical properties of the alloy.

Synthesis of Highly-Selective Fibrous Adsorbent by Introducing 2-Ethylhexyl Hydrogen-2-Ethylhexylphosphonate for Scandium Adsorption

2-ethylhexyl hydrogen-2-ethylhexylphosphonate (EHEP) is commonly used as a metal extractant because it has a particular affinity for rare-earth metals like Scandium (Sc). To develop a highly-selective adsorbent of Sc(III), EHEP was introduced as a functional group onto a polyethylene fabric with radiation-induced graft polymerization(RIGP). The adsorption performances for Sc(III) were evaluated with aqueous solutions containing Sc(III) and Fe(III) in bath and column tests. As a result of column test, the adsorption capacities of Sc(III) and Fe(III) until the bed volume reached 5000 were 5.22 and 0.12 mg/g, respectively. It means that the amount of collected Sc(III) by the EHEP adsorbent was approximately 44 times higher than that of Fe(III). These results indicate that the grafted adsorbent containing EHEP has an extremely high selectivity for Sc(III) adsorption.

Extraction Separation of Scandium，Iron and Lutetium with Isopropyl Phosphonic Acid Mono（1－hexyl－4－ethyl）OctylEster

The extraction and stripping of scandium from its sulfate solutions by isopropyl phosphonic acid mono (1-hexyl-4-ethyl) octyl ester (PT-2, HL) diluted with n-hexane are reported. A high efficiency of separation between scandium, iron and lutetium can be achieved by controlling aqueous acidity. Different mechanisms of Sc3+ with PT-2 in various acid range have been proposed.At lower aqueous acidity, it is a cation exchange reaction, while at higher acidity. a solvation reaction was ascertained. Its IR and NMR spectra have been discussed. The effect of temperature on extraction of Sc3+ was observed and thermodynamic functions were calculated.

Separation of Scandium and Rare Earths with the Method of PSO-Extraction Chromatography

Separation of scandium and rare earths was investigated by using a new extraction chromatography which PSO was used as a stationary phase,while HCl-NH_4SCN solution as a mobile phase.The separation conditions were studied.In this system, the separation factor(β_(Nd)^(Sc))can reach up to 1.3×10~4.The method can be applied to the purposes of separation,purification and analysis of microquantity of Sc in the mixed rare earth.

Reduction Mechanism of Scandium Ion in Fluoride Salt Melt

The electrochemical behavior of Sc^(3+) in LiF-NaF system was investigated. The cyclic voltammetry and chronopotentiometry were used to investigate the reduction mechanism of the electrochemical deposition of Sc^(3+) to Sc on Ag electrode in LiF-NaF system at 1043 K. Experimental results indicate that the electroreduction of Sc^(3+) to Sc is a reversible process with simple 3-electron transfer in one step controlled by diffusion.

Sensitizing Effect of Mixed Surfactants on the Colouration of Scandium(Ⅲ)with Phenylfluorone or Its Derivatives

In the presence of mixed micelle of a cationic and a nonionic surfactants,the reaction of scandium(Ⅲ) with phenylfluorone or its derivatives results in a very sensitive colouration:furthermore this chromophoric system tolerates the existence of a considerable amount of masking agents,so that many interfering ions can be masked and its selectivity would be further improved.After studying the optimum conditions and main charac- ters of some similar systems,the system of Sc(Ⅲ)—Orthonitrophenyuorone—Cetyltrimethylammonium Bromide(CTMAB)—Triton X-200 is chosen for the spectrophotometric determination of microamount of scandium.The proposed method shows not only high sensitivity(with a molar absorptivity of 2.12×1~sL mol^(-1)·cm^(-1))and selectivity,but also high tolerance of chromophoric conditions.Beer's law is obeyed over a range of 0～6.0 μg Sc/25ml.If the dual-wavelength method is applied,a much higher molar absorptivity o|' 3.04×10~5L·mol^(-1)·cm^(-1)than those of other systems ever reported in the literatures can be attained:more- over.its linear range is extended to 0～8.0 μg Sc/25ml and its reproducibility is also improved.

Ion Flotation of Scandium

Scandium was recovered from dilute chloride solutions with potassium salt of saturated C_8～C_(12)fatty acids as surfactant by Ion flotation.The optimum comprehensive results of physical properties,stability and scandium concentration of the foam formed with potassium caprate CH_3(CH_2)_8 COOK can be obtained.Re- covery of scandium in the foam was 98% at pH 3.8～5.0 and 25～55℃.The experimental results of 0.3 L/min airflow rate was satisfactory for flotation column.It is of a great potential for using ion flotation technique to concentrate scandium from dilute solutions.

DeterminationofMicroamountofScandiuminRareEarth

In the presence of some kinds of surfactants, the reaction of Sc(Ⅲ) with 3,5 di Br PADAP is very sensitive. After studying the optimum conditions and some characters of several systems, the system of Sc(Ⅲ) 3,5 di Br PADAP triton X 100 is chosen for the spectrophotometric determination of microamount of scandium. Furthermore, the dual wavelength spectrophotometric analytical method was employed for this system, the microamount of scandium in rare earth matrix can be directly analyzed without separation. The standard added recovery ratios for several real samples of rare earth ores were determined and the results were satisfied.

Study on Technology and Mechanism of Purifying Scandium Metal by Vacuum Distillation Method

The evaporation coefficients alpha(i) of impurity elements Al, Cu, Cr, Co, Fe, Ni, Si in liquid scandium metal of purity 99.9% were measured at 1550 degrees C and 6.7 x 10(-3) Pa. The separating coefficients beta(i) and activity coefficients gamma(i)(o) of these impurity elements were calculated and the separation possibility between these impurity elements and Sc was discussed from thermodynamics. Then the new technology in preparation of high purity scandium metal was proposed and its purification mechanism was discussed.

Preparation of Scandium Bearing Master Alloys by Aluminum Magnesium Thermoreduction

The new preparation method of scandium bearing master alloys, in which scandium oxide was fluorinated by reaction with NH 4HF 2 and then reduced by aluminum magnesium in fused salt containing alkali and alkaline fluoride under atmosphere, was studied. The effect of sorts of metallic reductive and technique conditions such as reducing temperature and time on the recovery of Sc was discussed. When the liquid aluminum magnesium was used as the reductive agent, the all recovery exceeds 80% and the concentration of Sc in master alloy prepared exceeds 1.9%. The best reducing reaction temperature and time are 1100 K and 40 min respectively. The newly produced Sc from reduction combines with Al to produce the stable compound Al 3Sc, so the reduction progress is sustained and the recovery of Sc is increased.

Fluorescence Enhancement of Samarium－Thenoyl－trifluoroacetone－Cetyltrimethylammonium Bromide－Triton X－100 by Scandium

fluorescence enhancement phenomenon shown by adding scandium ion to thesamarium-thenoyltrifluoroacetone (TTA)-cetyltrimethylammonium bromide(CTMAB)-Triton X-100(TX-100) system was observed and the effect of the condi-tions on the system was studied in detail. The excitation and emission wavelengthswere 370 nm, 565 nm, 603 nm and 645 nm, respectively. The optimum conditionsforming Sm-Sc-TTA-CTMAB-TX-100 system were that the concentration of Sc￣(3+)was equal to 5.0× 10￣(-5) mol/L, pH was 7. 7. Under these conditions, the fluores-cence intensity can be increased about 10 times higher than that of the system con-taining no Sc￣(3+) , and it was a linear function of the concentration of samariumn therange of 1. 0 × 10￣(-9)-4. 0 × 10￣(-7) mol/L. The detection limit was 6. 0 ×10￣(-10) mol/L.This system was used for the spectrofluorimetric determination of samarium withsatisfactory results. The nature of enhanced fluorescence was explained using in-tramolecular and intermolecular energy transfer theory.

Enrichment of Trace Scandium with Microcrystalline Naphthalene and Subsequent ICP-AES Determination

A new method is proposed to preconcentrate and separate trace scandium from a large volume of aqueous solution by solid liquid extraction with microcrystalline naphthalene. Scandium oxinate can be adsorbed onto microcrystalline naphthalene quantitatively under certain conditions. The effects of various experimental parameters have been optimized. The influence of additive of cobalt (II) on recovery of scandium (III) is studied in detail. The proposed method has been used for determination of Sc in Certified Reference Material of “Vehicle Exhaust Particulates”.