Determination of zirconium,thorium and scandium with 2,5-dihydroxy-1,4-benzoquinone

Zirconium is quantitatively precipitated by 2,5-dihydroxy-1,4-benzoquinone and is separated from scandium in 1 N hydrochloric acid solution. Thorium is separated at pH 0.5 from uranium(VI), cerium(IV), lanthanum, yttrium and scandium. Scandium is quantitatively precipitated by this reagent in the pH range 1.4–2.0 and at pH 1.5 equivalent amounts of lanthanum do not interfere; small amounts of yttrium cause interference.     

Dynamic ion-exchange chromatography with post-column reaction detection for the determination of the rare earth elements in monazites

Summary Separation and determination of lanthanum, cerium, praseodymium, neodymium and samarium in monazites have been achieved by dynamic ion-exchange chromatography. The ore samples are decomposed by sulfuric acid and the rare earths are separated in a group as oxalates. The rare earth elements are then separated from each other on a column of bonded phase silica by gradient elution with 0.05 to 0.5 M lactic acid (pH 3.5) in the presence of 0.01 M sodium 1-octanesulfonate. Post-column reaction with Arsenazo III is used for detection and quantification of the individual rare earth elements. Results are quoted for lanthanum, cerium, praseodymium, neodymium and samarium in monazites. Detection limit is 1 μg ml⁻¹ with a S/N ratio of 3. The separation is complete within 27 min valley to valley resolution. Precision of better than 1% can usually be obtained.     

Separation and gravimetric determination of thorium and cerium(IV) with vanillin

Vanillin forms insoluble complexes with thorium and cerium(IV) at pH 4.0–6.2 and 2.5–7.0 respectively. Thorium and cerium can be determined gravimetrically and separated from each other as well as from uranium(VI) and typical trivalent rare earths. The precipitates obtained are ignited to the corresponding oxide and weighed; as little as 4.4 mg of ThO₂ and 4.9 mg of CeO₂ can be determined.     

Separation of lanthanum and cerium on modified fly ash bed

The adsorption of lanthanum and cerium on modified fly ash bed has been studied. The effect of pH on the adsorption of both lanthanum and cerium by the bed material has been discussed. The exchange capacities of lanthanum and cerium have been determined. The method has been applied to monazite sand solution. The elution of both lanthanum(III) and cerium(IV) was studied using buffer and suitable eluting agent. The process is simple and may be considered as a low cost-methodology for separation of lanthanum and cerium.     

Separation of lanthanum and cerium on modified fly ash bed

The adsorption of lanthanum and cerium on modified fly ash bed has been studied. The effect of pH on the adsorption of both lanthanum and cerium by the bed material has been discussed. The exchange capacities of lanthanum and cerium have been determined. The method has been applied to monazite sand solution. The elution of both lanthanum(III) and cerium(IV) was studied using buffer and suitable eluting agent. The process is simple and may be considered as a low cost-methodology for separation of lanthanum and cerium.     

Simultaneous determination of lanthanum and cerium in mixed rare earths with p-acetylarsenazo by spectrophotometry

A new method has been developed for the simultaneous spectrophotometric determination of small amounts of lanthanum and cerium in the presence of large amounts of rare earth elements. Lanthanum (III) and cerium (III) were determined spectrophotometrically with p-acetylarsenazo as the color reagent in the chloroacetic acid medium at pH 3.1 by measuring the absorbances of the complexes at 670 nm. The remained rare earths were masked with ethylenediaminetetracetic acid and ethylenediaminetetracetic acid-zinc during the analysis. The optimum conditions for the simultaneous determination of lanthanum and cerium have been defined. The individual content of lanthanum (III) and cerium (III) were determined by varying the amounts of EDTA and EDTA-Zn used in the analysis and solving the simultaneous absorbance equations based on the Beer's law. The proposed method has been successfully applied to the determination of lanthanum and cerium in Longnan mixed rare earth oxides and other heavy rare earths without preliminary separation with satisfactory results. The relative errors of all analytical results of the method were not more than 2% with good precision. The procedure does not require separation of lanthanum, cerium and the other rare earth elements.     

Chlorophosphonazo-m-NO2, a new reagent for the spectrophotometric determination of cerium sub-group rare earth elements in the presence of yttrium sub-group elements

The synthesis of chlorophosphonazo-m-NO₂ is described. Cerium sub-group rare earth elements can be determined in the presence of 10–40 fold amounts of yttrium sub-group elements when the latter are masked by oxalic acid at pH 1.6. Under the experimental conditions employed, the apparent molar absorptivities of lanthanum and cerium at 666 nm are 9.5 × 10⁴ and 9.3 × 10⁴ l mol^-1 cm^-1, respectively. Beer's law is obeyed for 0–12 μg of lanthanum or cerium in 25 ml of solution. The coefficients of variation for La and Ce are 0.37% and 0.92%, respectively.     

Reversed Phase Extraction Chromatographic Separation Of Scandium With Amberlite LA-1 From Malonate Solutions

Abstract

Scandium was extracted at pH 5.0 from 0.01 M malonic acid on silica gel column impregnated with Amberlite LA-1. Nickel, zinc, cadmium, mercury, lead, tin, aluminium, and lanthanum in binary mixtures because they could not form malonato complexes. It was separated by the process of selective elution from elements such as zirconium, thorium, uranium, iron(III), gallium, indium, cerium(III), litanium by exploiting difference in stability of malonato complexes. Scandium was separated from multicomponent mixture containing yttrium, titanium, zironium, thorium, uranium and aluminium by a process of selective sorbtion and selective elution.     

Separation of yttrium and neodymium from samarium and the heavier lanthanides by cation-exchange chromatography with hydroxyethylenediaminetriacetate in monochloroacetate buffer

Trace and mg amounts of yttrium and neodymium are separated from samarium and the heavier lanthanides by elution of the latter with hydroxyethylenediaminetriacetate (HEDTA) in a chloroacetate buffer of pH 2.85 from a column containing 68 ml (20 g) of AG 50W-X4 resin of 200–400 mesh particle size. Yttrium and neodymium (and also praeseodymium, cerium and lanthanum) are retained and can be eluted with 0.01M HEDTA in 0.20M ammonium acetate (pH 6). The separations are reasonably sharp and quantitative: only 3–15 μg of samarium was found in the yttrium fraction and 0.8–3.4 μg of yttrium in the samarium fraction when 4.41 mg of yttrium and 7.12 mg of samarium were present originally. Control of the pH during the column operations is essential because the peak positions are very sensitive to change in pH. The relevant distribution coefficients, elution curves of pairs of elements and results for the analysis of synthetic mixtures are presented. Also included is a method for separating yttrium and the lanthanides from HEDTA and sodium and ammonium ions.     

The thermolysis of the neocupferron chelates of yttrium and the rare earth elements

The thermolosis curves of the neocupferron chelates of yttnum, lanthanum, cerium(III), cerium(IV). praseodymium, neodymium, samarium and gadolinuim were determined. It was found that the ehelates were stable up to 8o°, with the oxide levels being reached at 460–750°.     

The oxinates of thorium and some cerite earths

The pH of precipitation of oxinates of thorium, cerium and lanthanum has been studied. By controlling the pH of precipitation, thorium has been separated as the oxinate.From a spectrochemical study of the 4 and 5 oxinates of thorium in dilute hydrochloric acid, acetone, carbontetrachloride, chloroform, and toluene, it has been suggested that the 5 complex is a definite compound, but not an addition body of the 4 compound.A colorimetric estimation of thorium has been suggested by measuring absorption at 320 mμ in hydrochloric acid and 330 mμ in acetone. 2 p.p.m. of the oxide has thus been estimated.     

Separation of rare earth elements in the tributyl phosphate–Ln(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>–Ca(NO<Subscript>3</Subscript>)<Subscript>2</Subscript> system in the counter current process

The 40-step extraction process to separate rare earth elements (RЕEs) according to the praseodymium–cerium line with the use of mixer–settler extractors in a 100% TBP–Ln(NO₃)₃–Ca(NO₃)₂ system is implemented. A lanthanum–cerium concentrate containing less than 0.03 wt % of the remaining REEs is obtained. The flow diagram of the separation process of a rare earth (RE) concentrate isolated from phosphogypsum is considered.     

Separation of <Superscript>139</Superscript>Ce using solvent extraction technique from La<Subscript>2</Subscript>O<Subscript>3</Subscript> target irradiated by 14.7 MeV protons

The radiochemical separation of no-carrier-added cerium from proton irradiated lanthanum was studied by solvent extraction using DEE, TBP and TPPO, the latter reagent being employed for the first time for separation of radiocerium from bulk of lanthanum. Distribution coefficients of cerium and lanthanum were investigated as a function of equilibrium time and concentration of HNO₃. A mixture of 0.05M K₂Cr₂O₇ and 0.1M H₂SO₄ was used as an oxidizing agent to improve the separation efficiency of cerium. A comparative study of the three extractants released that DEE is the best for separation of cerium from bulk of lanthanum oxide. The target was prepared by pressing. The production of ¹³⁹Ce of high radionuclidic purity and chemical purity via irradiation of lanthanum oxide target at MGC-20 cyclotron with protons of energy 14.5 MeV is described. The experimental yield was found to be 153 kBq/μA·h.     

Radiochemical study of the separation of cerium(III) from lanthanum by solvent extraction using N-benzoyl-N-phenylhydroxylamine

The extraction of cerium(III) and lanthanum(III) by N-benzoyl-N-phenylhydroxylamine (N-BPHA) in chloroform has been studied in order to determine the composition and extraction constants of the extracted chelates. From the results obtained, the best conditions for the separation of cerium from lanthanum (separation factor about 200) have been predicted and experimentally verified.     

Spectrophotometric determination of yttrium with molybdophosphoric acid

A simple sensitive spectrophotometric determination of yttrium, based on the reaction of molybdophosphoric acid with yttrium at pH 4.8, is described. The resulting complex is reduced and the absorbance measured at 695 nm. The method is applicable in the presence of several-fold excesses of lanthanum, cerium, and phosphate.     

Separation of molybdenum(VI) from other elements by solvent extraction with dibenzo-18-crown-6 from hydrochloric acid medium

DB-18-C6 was used for the extractive separation analysis of molybdenum(VI) from a range of other elements. Molybdenum(VI) was quantitatively extracted from 8M hydrochloric acid with 0.01M DB-18-C6 in nitrobenzene. It was stripped from the organic phase with 2M nitric acid and determined spectrophotometrically with Tiron at 390 nm. Molybdenum was separated from a large number of elements in binary mixtures, the tolerance limit for most elements being very high. Selective extraction of molybdenum permits its separation from barium, thorium, cesium, rubidium, strontium, lanthanum, chromium(III) and cerium(III). The method was extended for the analysis of molybdenum in a soil sample.     

The use of cerium(IV) phosphate for the gravimetric determination and separation of cerium

A method for the gravimetric determination of cerium as Ce₃(PO₄)₄ is described. Cerium can be separated from many metals in this form, as well as from permanganate and dichromate; the cerium separated can then be titrated with iron(II) solution. The method was verified for the determination of cerium in a rare earth concentrate.     

Substoichiometric precipitation of fluoride with lanthanum

The substoichiometric precipitation of fluoride with lanthanum was studied by using¹⁸F and¹⁴⁰La tracers and it was found that fluoride could be precipitated substoichiometrically with lanthanum and the reaction ratio between fluoride and lanthanum was 3∶1. The pH range at which fluoride can be separated substoichiometrically with lanthanum is between 2 and 8. Barium and indium interfere in the precipitation of fluoride, sodium, copper and manganese, however, not. Fluorosilicate can also be precipitated substoichiometrically by using lanthanum as a precipitant and the reaction ratio between fluorosilicate and lanthanum was 1∶2. This separation was applied for the determination of oxygen in silicon crystals. The concentration of oxygen measured in some silicon crystals was between 5 and 27 ppm and in good agreement with those by non-destructive method and infrared spectrophotometry.     

Spectrophotometric determination of rare earth metals with 1-(2-pyridylazo)-2-naphthol

1-(2-Pyridylazo)-2-naphthol (PAN) reacts very sensitively with rare earth metals to form a deep red precipitate in alkaline solution; this can be extracted with ether, except in the case of lanthanum, cerium and scandium. Absorption maxima occur at 530 and 560 mμ. Traces of rare earth metals may be determined in the presence of many foreign metals.     

The determination of lanthanum,cerium and thorium without separations: The determination of lanthanum and cerium in thorium

A method is proposed for the spectrophotometric determination of small quantities of lanthanum, cerium and thorium in the presence of one another without separations. Cerium is estimated from its absorption peak in the ultraviolet region, thorium with thorin, and the 3 elements together with arsenazo. The lanthanum is calculated after subtraction of the combined absorbances of the arsenazo complexes of the thorium and cerium. The procedure can be readily applied to the determination of microgram amounts of the 2 rare earths in thorium. In this case the majority of the thorium is removed from the solution by solvent extraction with TTA before the estimation of the rare earths. The interference of iron is considered and proposals made for its removal.