Cation-exchange separation of hafnium and zirconium from accompanying ions

Hafnium and zirconium are not retained on the strongly acidic cation-exchange resin Dowex 50 from a mixture consisting of methanol and 12M nitric acid (19:1) which is 0.1M in trioctylphosphine oxide. On the other hand most other elements investigated are strongly adsorbed on the resin from this medium so that they are readily separated from hafnium and zirconium. These elements include titanium, rare earths, alkali metals, alkaline earth metals, iron, cobalt, manganese and zinc. This separation technique has been found to be suitable for the separation of tracer and milligram amounts of hafnium and zirconium from accompanying metal ions. If in place of methanol other organic solvents such as acetone, tetrahydrofuran and methyl glycol are used the selectivity of the separation of zirconium and hafnium from the other elements is decreased. The same effect is observed when hydrochloric acid is used in the mixtures instead of nitric acid.     

Separation of zirconium by thin-layer chromatography

The thin-layer Chromatographie separation of a number of metal ions [Sc, Y, Zr, La, Sm, Th, U(VI), etc.] with solvent mixtures of mesityl oxide, ethanol and 5M nitric acid on silica gel-cellulose (5:1) thin-layer plates is reported. Zirconium remains stationary whilst the other metal ions move with the solvent, thus allowing a selective separation of zirconium from about 20 metal ions in ratios ranging from 100:1 to 1:100. Mixtures of various metal ions can also be separated.     

Liquid-liquid extraction of tungsten(VI) with mesityl oxide application to an alloy steel

A new and simple method has been developed for the rapid extraction of tungsten(VI) with mesityl oxide. Quantitative extraction occurs from solutions 1M in hydrochloric acid and 12M in lithium chloride (as the salting-out agent) with 75% mesityl oxide in isobutyl methyl ketone. Tungsten is finally determined photometrically as the thiocyanate complex in the aqueous phase. Tungsten-(VI) can be extracted and determined satisfactorily in the presence of several elements. The method is shown to be applicable to an alloy steel.     

Simple spectrophotometric method for determination of zirconium or hafnium in selected molybdenum-base alloys

A simple analytical procedure is described for determining zirconium or hafnium in molybdenum-base alloys by formation of the Arsenazo III complex of zirconium or hafnium in 9 M hydrochloric acid medium. The absorbance is measured at 670 nm. Molybdenum (10 mg), titanium (1 mg), and rhenium (10 mg) have no adverse effect. No prior separation is needed. The relative standard deviation is 1.3-2.7%.     

Separation of selenium(IV) and tellurium(IV) from mixtures by extraction chromatography with trioctylphosphine oxide

The reversed-phase extraction chromatographic separation of selenium(IV) and tellurium(IV) from several elements with trioctylphosphine oxide as extractant is reported. Selenium was extracted from 6M hydrochloric acid containing 7M lithium chloride was stripped with 4M hydrochloric acid, and tellurium was extracted from either the same medium as selenium or from 4M hydrochloric acid, and stripped with 1-2M hydrochloric acid. Selenium and tellurium can be separated from multicomponent mixtures.     

Extractive separation of group IVB elements: analysis of alloy samples

A method is proposed for the extraction and mutual separation of quadrivalent titanium, zirconium and hafnium from hydrochloric acid using triphenylphosphine oxide dissolved in toluene as an extractant. The optimum conditions for the extraction and separation have been evaluated from critical study of acid concentration, extractant concentration, period of equilibration and effect of diluent. The effect of foreign ions on the extraction and determination is also discussed. The probable composition of the extracted species has been deduced from logD-logC plots. The method affords mutual separation of titanium, zirconium and hafnium and is applicable to the analysis of alloy samples.     

Selective Determination of Hafnium with Solid Surface Room Temperature Phosphorescence Optosensing

Abstract

An optosensing method for selective determination of hafnium has be developed. It is based on the phenomenon that when the complex formed by 8-hydroxy-5-quinolinesulfonic acid with hafnium is absorbed on the strongly basic anion exchange resin, the phosphor can produce room temperature phosphora-scence (RTP) in aqueous medium. The hafnium can be determined selectively in the presence of zirconium. The RTP intensity is linear up to 4×10^-5 M of hafnium, the detection limit is found to be 5×10^-8 M of hafnium.     

Spectrofluorimtric determination of hafnium with 3-hydroxychromone

The fluorescence of the 1:1 hafnium—3-hydroxychromone complex in 4—0.5 M hydrochloric acid is used to determine 0.4—9.0 μg of hafnium in 25 ml of solution; the relative standard deviation is 0.15%. Zirconium does not interfere in 2-fold amounts.     

Trennung von Zirkonium- und Hafnium-Komplexen an Ionenaustauschern

Zusammenfassung Mit Hilfe von 8-Hydroxychinolin-5-sulfonsäure als Komplexbildner konnte ein Trennverfahren für Zirkonium und Hafnium an Ionenaustauschern entwickelt werden. Es nutzt die Unterschiede der Komplexstabilitäten der Sulfoxinato- und der Sulfato-Komplexe:Mit 1 N Schwefelsäure wird nur das Zirkonium abgelöst, wogegen das Hafnium erst mit stärker konzentrierter Schwefelsäure oder Oxalsäure eluiert wird. Der Nachweis der Leistungsfähigkeit dieses Trennverfahrens erfolgte anhand der Reinigung von handelsüblichen Zirkonium- und Hafniumsalzen.ICP-Messungen ergaben, daß mit Hilfe dieses Verfahrens in einem Analysengang reaktorreines Zirkonium hergestellt werden kann. Eine weitgehende Entfernung der Zirkoniumbeimengungen aus dem Hafniumsalz ist möglich.

---

Separation of zirconium- and hafnium-complexes by means of ion-exchangers

Summary A separation of zirconium and hafnium on ion-exchangers was obtained by use of 8-hydroxyquinoline-5-sulfonic acid as chelating agent.The separation is based on the difference in the stability of the sulfoxinate- and sulfate-complexes.Using 1 N sulfuric acid as eluent only zirconium can be removed, whereas the elution of hafnium is foremost obtained with higher concentrated sulfuric or oxalic acid. The evidence of the efficiency of this separation process can be demonstrated by the purification of commercial zirconium- and hafnium-salts. The ICP-measurements gave the result, that it is possible to obtain reactor-pure zirconium in one separation step and to remove nearly all zirconium impurities from the hafnium salt.

     

Adsorption behavior of Zr, Hf, Nb, Ta and Pa on macroporous anion exchanger in NH4SCN/HClO4 and NH4SCN/HF media

The possible use of thiocyanate and ammonium thiocyanate-hydrofluoric acid mixtures for quantitative anion exchange separation of zirconium from hafnium and niobium from tantalum and protactinium has been investigated. Distribution coefficients of zirconium(IV), hafnium(IV), niobium(V), tantalum(V) and protactinium(V) on macroporous BIO-RAD AGMP1 resin over a wide range of SCN and SCN/HF concentrations have been determined. The simultaneous presence of these two complexing agents causes a strong decrease of the adsorption phenomena.     

Sorption of hafnium on hydrous titanium oxide using radiotracer technique

The sorption of hafnium on hydrous titanium oxide (TiO₂·1.94 H₂O) has been studied in detail. Maximum sorption of hafnium can be achieved from a pH 7 buffer solution containing boric acid and sodium hydroxide using 50 mg of the oxide after 30 minutes shaking. The value ofk _d, the rate constant of intraparticle transport for hafnium sorption, from 0.01M hydrochloric and perchloric acid and pH 7 buffer solutions has been found to be 17 mmole·g^–1·min^–2. The kinetics of hafnium sorption follows Lagergren equation in 0.01M HCl solution only. The values of the overall rate constantK=6.33·10^–2 min^–1 and of the rate constant for sorptionk ₁=6.32·10^–2 min^–1 and desorptionk ₂=2.28·10^–5 min^–1 have been evaluated using linear regression analysis. The value of correlation factor() is 0.9824. The influence of hafnium concentration on its sorption has been examined from 4.55·10^–5 to 9.01·10^–4 M from pH 7 buffer solution. The sorption data followed only the Langmuir sorption isotherm. The saturation capacity of 9.52 mmole·g^–1 and of a constant related to sorption energy have been estimated to be 2917 dm³·mole^–1. Among all the additional anions and cations tested only citrate ions reduce the sorption significantly. Under optimal experimental conditions selected for hafnium sorption, As(III), Sn(V), Co(II), Se(IV) and Eu(III) have shown higher sorption whereas Mn(II), Ag(I) and Sc(III) are sorbed to a lesser extent. It can be concluded that a titanium oxide bed can be used for the preconcentration and removal of hafnium and other metal ions showing higher sorption from their very dilute solutions. The oxide can also be employed for the decontamination of radioactive liquid waste and for pollution abatement studies.     

Extraction of chromium(VI) with 4-methyl-3-pentene-2-one and subsequent photometric determination as diphenylcarbazide complex

Summary A rapid and sensitive method is developed for the solvent extraction of chromium(VI) with mesityl oxide. Chromium(VI) is extracted with pure mesityl oxide from 1 M HCl containing 2.5 M KCl as salting-out agent. The metal from the organic phase is stripped with dilute ammonia and determined photometrically as its dephenylcarbazide complex at 540 nm. Chromium(VI) can be extracted in presence of a large number of ions. Only 30 min are required for complete separation and determination. Average recovery was 98.6 ± 1.4%, the standard deviation ± 1.3% (14.9 g of Cr).

---

Extraktion von Chrom(VI) mit 4-Methyl-3-penten-2-on und anschlieende photometrische Bestimmung als Diphenylcarbazidkomplex

Zusammenfassung Chrom wird mit reinem Mesityloxid aus 1 M salzsaurer, 2,5 M KCl enthaltender Lösung extrahiert, mit Ammoniaklösung aus der organischen Phase entfernt und photometrisch als Diphenylcarbazidkomplex bei 540 nm bestimmt. Zahlreiche Fremdionen stören die Extraktion nicht. Für Abtrennung und Bestimmung werden 30 min benötigt. Im Durchschnitt wurden 98,6 ± 1,4 % wiedergefunden. Die Standard-abweichung betrug ± 1,3% (für 14,9 g Cr).

     

Reactions of Unsaturated Ketones with Bis(trimethylsilyl) Hypophosphite

Bis(trimethylsilyl) hypophosphite reacts with unsaturated ketones (methyl vinyl ketone and mesityl oxide) to give, depending on the reaction conditions, 1: 1 or 1: 2 adducts after hydrolysis. It was found that the intramolecular cyclization of the 1: 2 reaction product with mesityl oxide, trimethylsilyl bis(2-methyl-4- oxopentan-2-yl)phosphinate, yields, after hydrolysis, a phosphorinane with exocyclic carbonyl and hydroxyl groups.     

Solvent extraction of hafnium(IV) by N-benzoyl-N-phenylhydroxylamine

The extraction of hafnium(IV) tracer by N-benzoyl-n-phenylhydroxylamine (BPHA) from 1M perchloric acid has been investigated and stability constants have been calculated for the complexes Hf(BPHA)(i)((4-i)+) (i = 1cdots, three dots, centered4). It was found that variation of perchlorate concentration in the range 0.5-2.0M at constant acidity has no effect on the distribution of hafnium.     

Extraction and separation of bismuth(III)

Separation of bismuth from beryllium, lead, iron(III), indium, scandium, lanthanum, antimony(III), zirconium, titanium, thorium, vanadium(V), molybdenum(VI), uranium (VI) and chromium(VI) is achieved by selective extraction of bismuth from 0.1M sodium salicylate solution (adjusted to pH 7) into mesityl oxide (MeO). The extracted species is Bi (HOC(6)H(4)COO)(3).3MeO. The results are accurate within +/- 0.5%, with a standard deviation of 0.8%. The separation and determination of bismuth takes only 15 min.     

Separation studies of molybdenum(VI) and rhenium(VII) using TPPO as an extractant

A simple, rapid and reproducible method for the extractive separation of molybdenum(VI) and rhenium(VII) is proposed using triphenylphosphine oxide (TPPO) dissolved in toluene as an extractant. The extractions are carried out from the hydrochloric and hydrobromic acid medium. The extraction of molybdenum is quantitative from 2.54-3.10 M hydrochloric acid and from 3.76-3.98 M hydrobromic acid, and that of rhenium is from 6.78-7.91 M hydrochloric acid. The probable nature of the extractable species is established using log distribution ratio-log concentration plots. The method permits mutual separation of molybdenum(VI) and rhenium(VII) and is applicable for the analysis of alloys and pharmaceutical sample. The detection limits for molybdenum(VI) and rhenium(VII) are 0.8 ppm and 4 ppm respectively.     

Extraction studies of copper with mesityl oxide

Summary A method has been developed for the extraction of copper(II) both at microgram and milligram level from bromide media using mesityl oxide as an extractant. The copper-bromo complex formed at 3.5 mol/l hydrobromic acid concentration showed quantitative extraction into mesityl oxide. Various experimental parameters such as acid concentration, period of equilibration, stripping agents and diverse ions have been studied. The stripped metal ion is monitored spectrophotometrically or by atomic absorption spectrometry (AAS). The method is applicable to the analysis of pharmaceutical and alloy samples.     

Liquid-liquid extraction of zirconium from hafnium and other elements with dicyclohexyl-18-crown-6

Zirconium was quantitatively extracted with 2.5 × 10^?2 M dicyclohexyl-18-crown-6 in dichloromethane from 8.5 M hydrochloric acid. It was stripped with 0.5 M hydrochloric acid and was determined spectrophotometrically as its complex with Arsenazo III. Hafnium was not extracted under these conditions, but from the residual aqueous phase it was extracted with 7.0 × 10^?2 M dicyclohexyl-18-crown-6 in dichloromethane from 9.0 M hydrochloric acid. It was stripped with 0.1 M perchloric acid and determined spectrophotometrically at 540 nm as its complex with xylenol orange. The separation of zirconium and hafnium from other metals is also described.     

Determination of zirconium and hafnium with xylenol orange and methylthymol blue

Both Xylenol Orange and Methylthymol Blue are highly selective and sensitive reagents for zirconium and hafnium forming intensely red complexes in an acidic medium. The factors affecting the color formation have been studied. The properties of the complexes have been determined and compared. In general, zirconium forms a more stable complex with the two dyes than hafnium, and Xylenol Orange forms a stronger complex with either zirconium or hafnium than Methylthymol Blue. Hydrogen peroxide can completely mask the zirconium complexes of either dye but only slightly affects the hafnium complex of Xylenol Orange. Zirconium and hafnium can both be determined without separation using peroxide as a masking agent and sulfate as a demasking agent. A bleaching reaction was observed when small amounts of hafnium were added to the red zirconium complex of Methylthymol Blue in 2.4 N perchloric acid or a small amount of zirconium was added to the red hafnium complex of Methylthymol Blue solution at pH 2 to 3.     

Development of a high-resolution inductively-coupled argon plasma apparatus for derivative spectrometry and its application to the determination of hafnium in high-purity zirconium oxide

A high-resolution apparatus for inductively-coupled plasma emission spectrometry (ICPES) has been developed, based on an echelle spectrometer modified for wavelength modulation with a quartz refractor plate. The selectivity of the technique is thus improved, and small amounts of hafnium in high-purity zirconium oxide can be determined directly without prior separation or preconcentration. A straight-line calibration curve passing through the origin is obtained without any correction for the interference from zirconium which exists in large excess. The detection limit for hafnium is 0.06 microg/ml, and the relative standard deviation (10 replicates) for hafnium at the 1.2 microg/ml level is about 3%.