Ion exchange of Cs+ and Sr2+ by natural clinoptilolite from bi-cationic solutions and XRD control of their structural positioning

Journal of Radioanalytical and Nuclear Chemistry - Clinoptilolite from Bulgaria was tested for uptake towards Cs+ and Sr2+ from bi-cationic solutions using batch technique. Contact time and cation...     

Study of the kinetics and mechanism of Sr2+ sorption by clinoptilolite

Journal of Radioanalytical and Nuclear Chemistry - The parameters of kinetics of Sr2+ sorption by natural clinoptilolite were investigated. The overall rate constants were determined by application...     

Selective amperometric titration of molybdenum with oxine in presence of DCTA

Summary In presence of DCTA molybdenum is selectively precipitated with oxine. The precipitation may be utilized for a volumetric determination with amperometric end-point detection. The influence of the ions which usually accompany molybdenum was established from the values obtained for the conditional solubility products of their oxinates. The behaviour of Cu(II), Fe(III), W(VI) and Al(III) was studied experimentally. It is shown, that Cu, Fe and W are completely masked by DCTA, Al was masked with NH₄F.Correct results are obtained with Mo concentrations in the initial solution >1×10^–5 and 1sx10^–3 M. The standard deviation of the method amounts to ±0.02 mg, while the relative (%) standard deviation varies within 0.2 to 2.0.

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Selektive amperometrische Titration von Molybdän mit Oxin in Gegenwart von DCTA

Zusammenfassung Molybdän(VI) läßt sich mit Oxin in Anwesenheit von DCTA selektiv fällen. Die Reaktion kann zur volumetrischen Bestimmung verwendet werden, wobei der Äquivalenzpunkt amperometrisch ermittelt wird. Der Einfluß von Metallionen wird auf Grund der berechneten relativen Löslichkeitsprodukte der entsprechenden Oxinate geschätzt. Experimentell wurden die Schlußfolgerungen für das Verhalten von Cu(II), Fe(III), W(VI) und Al(III) geprüft. Die ersten drei werden nicht mitgefällt, während Al durch F^–maskiert werden kann. Der Anwendungsbereich der Methode umfaßt Mo(VI)-Konzentrationen >1·10^–5 und 1·10^–3 M. Die Ionen von Cu, Fe, Al und W, sowie diejenigen, welche leichter lösliche Oxinate bilden, stören nicht. Die Reproduzierbarkeit wird durch eine Standardabweichung von ±0,02 mg bzw. eine relative (%) Standardabweichung von 0,2–2,0 charakterisiert.

     

Application of sodium carbonate-zinc oxide decomposition mixture on ICP-AES determination of boron in tourmaline

Boron in tourmaline, a high refractory mineral with a high boron content (approximately 3%), can be determined after aqueous leaching of a sodium carbonate-zinc oxide melt. Boron is separated effectively from the major elements of matrix, such as silicon, calcium and magnesium and especially from iron, the main spectral interfering element. Measurements were performed by inductively coupled plasma atomic emission spectrometry. A determination limit of 4 microg/g could be achieved when 200 mg of sample are analyzed with a precision of 5.2% RSD. This method could be applied to the determination of fluorine in the same solution.     

Extraction-spectrophotometric determination of zinc(ii) with 4-(2-pyridylazo)-resorcinol and a quaternary ammonium salt

A simple and sélective extraction spectrophotometric determination of zinc is described. The complex [Zn(PAR)(2)](CDBA)(2), where PAR is the 4-(2-pyridylazo)resorcinol anion and CDBA is cetyldimethylbenzylammonium ion, is extracted from a solution buffered at pH 9.7 with carbonate/bicarbonate. Beer's law is obeyed over the range 0.2-1.2 ppm zinc, the molar absorptivity being 9.2 x 10(4) 1 .mole(-1).cm(-1). The precision in this range is 0.0056 ppm. Cadmium in up to a 50-fold w w ratio may be masked with diethyldithiocarbamate.     

Arsenic solubility, mobility and speciation in the deposits from a copper production waste storage

The sediments in large pond for discharge of waste products of metallurgical activity were studied with respect to the valence forms of arsenic and its mobility. A sequential extraction procedure for arsenic compounds was applied and optimized according to the nature of analyzed products. During the first stage, the content of water-soluble arsenic compounds was determined, during the second—HCl-soluble forms and during the third—compounds soluble in sodium hydroxide. The optimum conditions for leaching arsenic from sediments (sample weight, concentration and volume of extractants, time of treatment) were established for each fraction.Speciation studies for determining As(III) and As(V) were carried out in the obtained arsenic extracts. The ability of the proposed sequential extraction procedure to specify the valence forms of inorganic arsenic was evaluated using model samples with added As(III) and As(V) and the recovery of spikes has been assessed. It was found that oxidation of As(III) and processes of sorption and sedimentation of As(V) proceed upon dissolution. A depth profiling was performed of the content of diverse forms of Às in two sites. The content of water-soluble As does not exceed 7.4% of total As in the sediments, As(III) being lower than 7.4% of that of the extracted As. The bulk of arsenic compounds (above 78% As) is dissolved in 2M HCl, and As(V) was found to be more than 94% of extracted arsenic. The analytical features of the procedure are as follow: precision, evaluated through the repeatability w > 0.96 and accuracy, estimated by the recovery above 93%, calculated on the basis of a twice repeated analysis of a series of 9 samples.     

Application of sodium carbonate-zinc oxide decomposition mixture on ICP-AES determination of boron in tourmaline

Boron in tourmaline, a high refractory mineral with a high boron content (～3%), can be determined after aqueous leaching of a sodium carbonate-zinc oxide melt. Boron is separated effectively from the major elements of matrix, such as silicon, calcium and magnesium and especially from iron, the main spectral interfering element. Measurements were performed by inductively coupled plasma atomic emission spectrometry. A determination limit of 4 μg/g could be achieved when 200 mg of sample are analyzed with a precision of 5.2% RSD. This method could be applied to the determination of fluorine in the same solution.     

On the copper(II)-EDTA-par system for visual and photometric end-point detection in iron(III)-EDTA titrations

The copper(II)-EDTA-PAR system is proposed as indicator for direct EDTA titration of 0.2-20 mg of iron(III) in acetic acid medium. The precision and accuracy have been evaluated by spectrophotometric titration. Microtitrations determine down to 10 mug of iron. A logarithmic concentration diagram has been constructed to present the complex equilibria involved. In an interference study the masking agent ammonium fluoride was found to improve the end-point detection. The method has been applied successfully to practical standard samples and compares favourably with other EDTA titrations of iron.     

Determination of Hf, Sc and Y in geological samples together with the rare-earth elements

 A method is described for the determination of Hf, Sc and Y simultaneously with the REE in geological materials. An earlier method for REE separation from major elements was studied with the aim to apply it also to the determination of Hf, Sc and Y. Sample decomposition was carried out by melting with LiBO₂. The method involves separation and concentration stages, using the cation-exchange resin DOWEX AG 50W-X8. Matrix elements were eluted with 2 mol/l HCl, whereas 6 mol/l HNO₃ with oxalic acid and 8 mol/l HNO₃ were used to elute the elements to be determined. Some of the matrix elements could not be completely removed. This effect as well as the recovery rates of the determined elements were investigated. The measurements were performed by ICP-AES. Spectral interferences were also tested. Received: 8 November 1995/Revised: 12 March 1996/Accepted: 14 March 1996