Marek Smolik

Determination of microamounts of hafnium in zirconium using inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry during their separation by ion exchange on Diphonix chelating resin.

Inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICPMS) methods were applied to check the possibility of determination of hafnium in zirconium at a level lower than 100 ppm. A zirconium matrix of hafnium content lower than 10 ppm was obtained using a worked-out separation method exploiting ion exchange on Diphonix resin. Both methods give results in good agreement with each other as well as with those for certified reference material BCR-098 (Zircaloy-4). They were utilized in determination of Hf in the samples collected during separation of microamounts of hafnium from zirconium by the mentioned ion exchange. These results proved the earlier described method of separation on Diphonix resin to be effective even when the initial concentration of hafnium in zirconium decreases from 2.4% to 0.0082%.

Method of low tantalum amounts determination in niobium and its compounds by ICP-OES technique

A method of determination of low amounts of tantalum in niobium and niobium compounds without its prior separation by means of inductively coupled plasma optical emission spectrometry (ICP-OES) has been worked out. The method involves dissolution of the analyzed samples of niobium as well as its various compounds (oxides, fluorides, chlorides, niobates(V)) in fluoride environments, precipitation of sparingly soluble niobic(tantalic) acid (Nb2O5(Ta2O5) · xH2O), converting them into soluble complex compounds by means of oxalic acid with addition of hydrogen peroxide and finally analyzing directly obtained solutions by ICP-OES. This method permits determination of Ta in niobium at the level of 10(-3)% with relatively good precision (≤ 8% RSD) and accuracy (recovery factor: 0.9-1.1). Relative differences in the results obtained by two independent methods (ICP-OES and ICP-MS) do not exceed 14%, and other elements present in niobium compounds (Ti, W, Zr, Hf, V, Mo, Fe, Cr) at the level of 10(-2)% do not affect determination.

Extraction of Zirconium and Hafnium in Polyethylene Glycol‐Based Aqueous Biphasic System

Abstract The behavior of zirconium and hafnium in PEG 2000‐Na2SO4‐HCl aqueous biphasic system has been investigated. The dependences of HCl concentration (0.185–0.55 M), extraction temperature (298–318 K), and extraction time (5–120 min) on distribution ratios have been determined. Extraction of this metals in PEG 2000‐Na2SO4‐H2SO4 and PEG 2000‐Na3Cit‐HCl systems has been also studied. The sulfate and citrate complexes of Zr and Hf prefer salt‐rich phase in contrast to chloride complexes which pass into PEG rich phase in about 50% (w/w) to the greatest degree in room temperature and at short extraction time. The increase of distribution ratios (D*Zr=3.75, D*Hf=4.31) was observed after addition of water soluble organic ligand ‐ tiron (4,5‐dihydroxy‐m benzenedisulfonic acid disodium salt). The results obtained in studied conditions are not very useful for the separation of zirconium and hafnium.

The Effects of Concentrations of Zirconium(IV) Sulphate and Sulphuric Acid on Sorption of Zirconium(IV) and Hafnium(IV) on Purolite S-957 Resin. Adsorption Isotherms of Zirconium(IV) and Hafnium(IV) Ions

The optimal conditions of separation of zirconium(IV) from hafnium(IV) on Purolite S-957 ion-exchange resin in their sulfate aqueous solutions using a static method has been determined to be 0,07 M Zr(SO4)2 (containing 2% Hf) in 0,5 M H2SO4. Higher Zr(IV) concentration causes a lowering of the Zr/Hf separation efficiency due to the oligocondensation of mononuclear Zr(IV) and Hf(IV) ions resulting in the formation of Zr(IV) or mixed Zr(IV)-Hf(IV) oligohydroxo-sulfato ions, which is not prevented by the parallel increase of acidity of the solution. The same effect can be observed when analyzing the shapes of adsorption isotherms, which are similar for both Zr(IV) and Hf(IV).

Determination of hafnium at the 10(-4)% level (relative to zirconium content) using neutron activation analysis, inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectrometry.

Hafnium at the very low level of 1-8 ppm (in relation to zirconium) was determined in zirconium sulfate solutions (originating from investigations of the separation of ca. 44 ppm Hf from zirconium by means of the ion exchange method) by using three independent methods: inductively coupled plasma mass spectrometry (ICP MS), neutron activation analysis (NAA) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The results of NAA and ICP MS determinations were consistent with each other across the entire investigated range (the RSD of both methods did not exceed 38%). The results of ICP-AES determination were more diverse, particularly at less than 5 ppm Hf (RSD was significantly higher: 29-253%). The ion exchange method exploiting Diphonix(®) resin proved sufficient efficiency in Zr-Hf separation when the initial concentration ratio of the elements ([Zr]0/[Hf]0) ranged from 1200 to ca. 143,000.

Pre-concentration of Ta(V) by solvent extraction before determination of trace amounts of Ta in Nb and Nb compounds

The paper presents the results of a study on the efficiency of the separation of Ta(V) and Nb(V) from fluoride solutions by solvent extraction with methyl isobutyl ketone with a view to applying the extraction process to the purification of Nb from Ta and for the pre-concentration of Ta prior to its determination in Nb and its compounds over a wide range of initial concentrations. With strict control of the hydrofluoric acid concentration and the re-extraction of Ta into an aqueous phase using an ammonium oxalate solution, the mean recovery factors [%] for Ta were 94–108% in the initial weight ratio mNb : mTa = (ρNb/Ta) range 10–1 000 000 with only a small scatter about the mean value (RSD ≤ 6%), with the exception of (ρNb/Ta) = 1 000 000. The effect of the composition of the re-extraction solution on the excitation conditions of Ta in ICP-OES (ICP-MS) plasma was negligible and small amounts of Nb and other contaminants co-extracted with Ta did not affect its determination.

The Effect of Foreign Ions on Separation of Hafnium from Zirconium on Diphonix® Resin

The weight distribution coefficients (λM) of the most often occurring in zirconium salts ions (M(II), M(III) and M(IV)) have been determined in established earlier optimal conditions for separation of zirconium from hafnium by means of Diphonix® resin. Their values range from 21 (λZn(II)) to 1830 (λTi(IV)) and depend on the charge of M ion as well as on its radius. For ions of the highest λM (Ti(IV) and Fe(III)) their influence on hafnium – zirconium separation has been studied. Ti(IV) ions at concentration of 1% (in relation to Zr) has been found to noticeably affect separation of hafnium from zirconium by means of Diphonix® resin.

Chemical, Physicochemical and Crystal-Chemical Aspects of Crystallization from Aqueous Solutions as a Method of Purification

While using crystallization for purification and separation of various substances, as well as for enrichment of trace amounts of new–found radioactive elements, it was established that (in addition to many others) chemical factors strongly affected the mentioned operations. Mechanisms of trace radioactive elements’ co-crystallization and the significance of these factors on their enrichment efficiency were reviewed in some works (Przytycka, 1968; Niesmeanov, 1975).

DISTRIBUTION OF MICROAMOUNTS OF M2+ DURING NiSO4·(NH4)2SO4·6H2O CRYSTALLIZATION

Distribution coefficients (D) of trace amounts of Co2+, Zn2+, Cu2+, Cd2+, Mn2+, Mg2+, Fe2+, and Ca2+ have been found during crystallization of NiSO4·(NH4)2SO4·6H2O at 25°C and 23°C. These values are affected mainly by solubilities of the corresponding double salts. Most of the microcomponent D values could be estimated from solubilities of their double salts. Some of the values are in good agreement with experimental data.