Separation Of Cerium Research Articles

Influence of alcohols on the extraction of cerium(IV) by Aliquat-336 in kerosene

Tricaprylmethylammonium chloride (Aliquat-336) diluted with kerosene was used to extract cerium(IV) from nitric acid medium. Various alcohols were used as modifiers to overcome the third phase problem. The different parameters affecting the extraction process including nitric, nitrate, hydrogen ion, extractant and metal concentrations as well as the temperature were separately investigated. The effect of the investigated alcohols on the extraction process was also studied in detail at two different concentrations and correlated to their physical constants. Based on the obtained results, the extraction equilibrium was deduced and the optimum conditions for the extraction of cerium(IV) were proposed. The method was tested and applied to the separation of cerium from the hydrous oxide cake resulting from monazite sand.

Selective extraction and preconcentration of cerium(IV) in water samples by cloud point extraction and determination by inductively coupled plasma optical emission spectrometry

Cloud point extraction (CPE) was used for the selective extraction and separation of cerium(IV) from aqueous solutions. The method is based on the formation of cerium(IV)-n-p-tolylbenzohydroxamic acid (n-TBHA) complex that is extracted into the micellar phase (Triton X-114) at a temperature above the cloud point temperature (CPT). After phase separation, the surfactant rich phase was diluted up to 1.0 mL and determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). Under the optimum extraction conditions and instrument parameters, by preconcentration of only 10.0 mL of sample in the presence of 0.09% Triton X-114, an enhancement factor of 13.8 was obtained. The analytical curve was linear in the range of 1.5–1200 µg L−1 and the detection limit was 0.4 µg L−1. The method was applied to the determination of Ce(IV) in water samples with satisfactory results.

An electrochemical process for the separation of cerium from rare earths

An electrochemical route to this oxidative precipitation was studied wherein a rare earth chloride solution is subjected to electrolysis enabling the separation of cerium as ceric hydroxide. A rotating cathode was used to avoid formation of hydroxide scale on the cathode surface. The electrolytic and solution parameters were optimized in laboratory scale and bench scale cells. The process occurred at a current efficiency of 60% with an energy consumption of 3.5 kWh/kg of CeO 2. The purity of the product was >95%.

Extraction and separation of cerium(IV) from nitric acid solutions containing thorium(IV) and rare earths(III) by DEHEHP

The extraction behaviour of Ce(IV), Th(IV) and part of RE(III), viz., La, Ce, Nd and Yb, has been investigated using di(2-ethylhexyl) 2-ethylhexyl phosphonate (DEHEHP,B) in heptane as an extractant. Results show that extractability varies in the order: Ce(IV)>Th(IV)⪢RE(III). Therefore, it is possible to find the appropriate conditions under which Ce(IV) can be effectively separated from Th(IV) and RE(III). Furthermore, stripping Ce(IV) from the loaded organic phase can be carried out by dilute H 2SO 4 with an aliquot of H 2O 2. Roasted bastnasite made in Baotou (China) by Na 2CO 3 and leached by HNO 3, there is about 50% Ce mainly as tetravalent nitrate along with other RE(III) and Th(IV) in the leachings. Through fractional extraction, taking nitric acid leachings of roasted Bastnasite as feed and DEHEHP as an extractant, we can obtain the CeO 2 products with high purity of 99.9–99.99%, with a yield of >85%, in which ThO 2/CeO 2<10 −4.

Modification in Purex process using supported liquid membrane separation of cerium(III) via oxidation to cerium(IV)from fission products from nitrate medium by SLM

The separation of cerium from fission products during Purex process have been achieved successfully. Cerium(III) has been oxidized to Ce(IV) by 9 M HNO 3 and 2 M NaBrO 3, Ce(IV) was stable for a long time (6 months) and separated from Uranium(IV) completely. The separation factor was found to be 3. The effect of 30% TBP–kerosene and different cations, Zr(IV) and Mo(VI) using supported liquid membrane on the extraction process have been studied. The effect of temperature has been studied and the activation energy of the reactions has been evaluated to be 19.04, 12.01 kcal/mol for Ce(III) and Ce(IV), respectively, which suggested that this process is chemical reaction controlled under this hydrodynamic condition. The membrane stability has been studied for a long time pertraction and in terms of adsorbed doses demonstrates the stability of membrane in such systems.

Solvent extraction of lanthanum (III) and cerium (III) from aqueous chloride solutions by LIX 70

The extraction and separation of cerium (III) from aqueous NaCl solutions with LIX 70® dissolved in kerosene or in n-heptane was investigated. The extraction of both metals has been found to depend on pH and on extractant concentration but not to depend on metal or chloride concentrations. The extraction constants calculated experimentally are log K ex = −16.15 for cerium and log K ex= −16.85 for lanthanum, It was found that both lanthanides are extracted as 1:3, metal: reagent complexes.

Radiochemical separation of cerium from natural uranium irradiated with thermal neutrons

Radiochemical separation of cerium from natural uranium irradiated with thermal neutrons

Separation of cerium from other lanthanides by leaching with nitric acid rare earth(III) hydroxide-cerium(IV) oxide mixtures

A simple operational method for separating cerium from other lanthanides in natural mixtures of cerium dioxide with lanthanide(III) hydroxides, obtained from Vietnamese parisite and Mongolian bastnasite, has been developed. The method is based on drying crude Ln(OH)3×H2O material in air at about 200°C within 6h, followed by leaching Ln(III) with concentrated nitric acid added carefully with stirring to the dried material/water 1∶1.5 slurry. Under optimum conditions cerium (and Th, if present) virtually does not pass into solution while the yield of leaching and the sum of REE oxides (REO) concentration in the after-leach solution reach the maximum values of 97% (mass) and 0.18 kg·dm−3, respectively. Besides an expected decrease of the leaching yield, roasting the starting material at 600°C results in over 7% Ce content in the Ln leached.

Separation of cerium and europium by extraction with tributyl phosphate and di(2-ethylhexyl)phosphoric acid in n-alkane from nitrate solutions

The following extraction systems have been studied: (Ce3++Eu3+) (NO3)-(EDTA, DCTA, DTPA)/TBP in n-alkane and (Ce3++Eu3+)(NO3)/DEHPA in n-alkane at concentration ratios as follows: [Ce3+]=trace −1 mol·dm−3, [Eu3+]=trace −0.1 mol·dm−3. [TBP]=(0.183−1.83) mol·dm−3, [DEHPA]=(5·10−3−0.1) mol·dm−3, [(H, Na)NO3]=(0.1−6) mol·dm−3, [Eu3+]: [EDTA, DCTA, DTPA]=1∶1−1∶10. The initial concentration of Eu3+ in aqueous phase in the extraction system containing a mixture of Ce3+ and Eu3+ was trace, 1% and 10% compared with the Ce3+ concentration. The distribution of the elements between the phases was observed radiometrically using141Ce,152Eu and154Eu. The results are documented by the distribution ratios DCe, DEu and separation factor α=DEu/DCe as functions of variable parameters of the systems.

Solvent extraction separation of cerium(III) from transition elements with 15-crown-5 with picrate as the counter ion

Cerium(III) was quantitatively extracted between pH 6.0 and 8.0 with 0.05 M 15-crown-5 in dichloromethane from 0.01 M picric acid with picrate as the counter ion. Cerium(III) was stripped with 1 M perchloric acid and determined spectrophotometrically at 655 nm as its complex with Arsenazo III. Cerium was separated from a large number of elements. Stepwise extraction of cerium permits its separation from thorium, uranium, scandium, yttrium and strontium. The method was applied to the determination of cerium in monazite sand.

Separation of cerium from other rare earths by photosensitization

Separation of cerium from other rare earths by photosensitization

Photochemical separation of cerium from rare earth mixtures in aqueous solution

Cerium has been separated from lanthanide mixtures by photochemical means. Separation is accomplished by photooxidation of Ce 3+ in acidic aqueous solution, followed by isolation of Ce 4+ by precipitation with iodate. Separation factors exceed 100 and total product yields exceed 95%. Quantum yields are estimated to be at least 0.10.

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

A method for the gravimetric determination of cerium as Ce 3(PO 4) 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.

N-oxides of 4-(5-nonyl)pyridine and trioctylamine as extractants for cerium(IV) and its separation from thorium(IV)

Trace level cerium has been oxidized to the quadrivalent state with potassium dichromate and shown to be preferentially extracted from very dilute mineral acid solutions and also from moderate nitric acid media by 0.1M solutions of 4-(5-nonyl)pyridine oxide and trioctylamine oxide dissolved in xylene. The dependence of extraction on the type of N-oxide, acid concentration and the N-oxide concentration has been investigated. The influence of the concentration of salting-out agents is described. Separation factors for a number of metal ions relative to cerium(IV) are reported for 0.1 M 4-(5-nonyl)pyridine oxide/xylene-0.1M sulphuric acid system. The ratio of the D for Ce(IV) to that of Ce(III) is greater than 105, and the D for Ce(IV) is much greater than that for thorium(IV). Separation of cerium(IV) from thorium has been achieved from 0.1M sulphuric acid solutions using 0.1M 4-(5-nonyl)pyridine oxide/xylene as an extractant.

The low gas flow rate foam separation of cerium (III) from dilute aqueous solutions

AbstractTwo low gas flow rate foam separation techniques, ion and precipitate flotation, have been investigated for the separation of trivalent cerium from solutions with initial cerium concentrations ranging from 1 × 10−8 to 1 × 10−4M in the pH range of 1.8–12 using the anionic collector sodium lauryl sulphate and the cationic surfactant cetyl trimethyl ammonium bromide. In addition to the type of collector, the pH and the cerium ion concentration, and other factors which can affect flotation results, viz. the time period of bubbling, the rate of gas flow, the ageing of both the cerium and the collector ions, the ionic strength, and the concentration of the collector ions have been investigated and optimum conditions have been established. Under optimum conditions removals as high as 98.5% can be achieved.

The low gas flow rate foam separation of cerium (III) from dilute aqueous solutions

Two low gas flow rate foam separation techniques, ion and precipitate flotation, have been investigated for the separation of trivalent cerium from solutions with initial cerium concentrations ranging from 1 × 10−8 to 1 × 10−4M in the pH range of 1.8–12 using the anionic collector sodium lauryl sulphate and the cationic surfactant cetyl trimethyl ammonium bromide. In addition to the type of collector, the pH and the cerium ion concentration, and other factors which can affect flotation results, viz. the time period of bubbling, the rate of gas flow, the ageing of both the cerium and the collector ions, the ionic strength, and the concentration of the collector ions have been investigated and optimum conditions have been established. Under optimum conditions removals as high as 98.5% can be achieved.

Chemical separation of cerium(III) fission nuclides from neutron irradiated uranium using N-oxides as solvents

Radiochemical cerium has been separated from young fission products by extraction of uranium and fission product nuclides using tri-n-octylamine oxide and an anion exchange column for preconcentration followed by extraction of cerium(IV) with 0.25M xylene solution of 4-(5-nonyl) pyridine oxide from 0.1M nitric acid. Cerium is then back extracted by reduction with HCl-H2O2 mixture.

Solvent extraction of trivalent actinides and lanthanides from a mixture of carboxylic and aminopolyacetic acids

The purity of di(2-ethylhexyl)phosphoric acid (HDEHP) markedly influenced the separation of cerium from americium in a lactic acid solution containing diethylenetriaminepentaacetic acid (DTPA) but had little influence on separations involving the least extractable rare earths, europium and promethium. Synergism occurred in the solvent extraction of these elements by mixtures of thenoyltrifluoroacetone (HTTA) and neutral organophosphates (S) from the same aqueous medium. This effect decreased as S was changed from a phosphine oxide, through phosphonate, to the neutral alkyl phosphates. Tracer studies showed that the composition of each extracting species is given by the general formula M(TTA) 3S 2 where M is a trivalent actinide or lanthanide. These species were independent of the diluent used but the extraction coefficients of the metal ions decreased by a factor of 10 4 from cyclohexane to chloroform. At a constant pH the extraction of americium and cerium was inversely proportional to DTPA concentration in the region 10 −3 −10 −1M. At lower DTPA concentrations the cerium dependence decreased rapidly while the americium increased until at 10 −4M concentration of DTPA the extraction order was reversed. When the DTPA concentration was constant the separation of cerium from americium increased with increasing pH, reaching a constant maximum at pH 2·6 and above.

Separation of cerium from americium

Separation of cerium from americium

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.