V.I. Fadeeva

Sorption of noble-metal ions on silica with chemically bonded nitrogen-containing ligands

A study has been made of the sorption of Ir(IV), Rh(III), Pt(IV), Ru(IV), Os(VIII), Pd(II) and Au(III) from aqueous solutions by silica chemically modified with nitrogen-containing organic ligands, as a function of hydrochloric acid concentration, time of contact, concentration of the element and the ionic strength. Sorption of noble-metal ions at pH > 1 on a sorbent containing monoamine groups seems to be due to a complexation mechanism, and to an anion-exchange mechanism at pH < 1. With aminopropyl-silica 1000-fold concentration of Ir(IV) and Rh(III) from their 10(-8)-10(-7)M solutions was achieved and these metals were subsequently determined on the sorbent surface by X-ray fluorescence. Detection limits were 10-20 ng/ml. There was no interference from 1000-fold quantities of non-ferrous metal ions and Fe(III). With the sorbent containing bonded diethylenetriamine groups, 1000-fold concentration of Au(III) was achieved, and it was then determined on the sorbent surface by an atomic-emission method. Conditions for desorption of Au(III) with pyridine and potassium thiocyanate were developed.

Concentration, separation and determination of scandium, zirconium, hafnium and thorium with a silica-based sulphonic acid cation-exchanger

A study has been made of the dependence of the sorption of scandium, zirconium, hafnium and thorium from aqueous solutions with a silica-based sulphonic cation-exchanger (SCE-SiO(2)) on the concentration and nature of the acid medium, time of contact, concentration of the element, and the ionic strength. The selectivity decreases in the order Zr approximately Hf > Th > Sc > Fe(III). The sorption characteristics of silica gel and SCE-SiO(2) have been compared, and the sorption mechanism is discussed. The SCE-SiO(2) exchanger has been used for 100-fold concentration of scandium, zirconium, hafnium and thorium from their 10(-8)-10(-7) M solutions, and a spectrophotometric method has been developed for their determination with a detection limit of 0.5 ng/ml for Zr and Sc and 0.1 ng/ml for Hf and Th. Zirconium and hafnium have been determined in the solvent phase by X-ray fluorescence and atomic-emission methods.

Preparation, properties and analytical application of silica with chemically grafted hydroxamic acid groups

Abstract The synthesis of silica chemically modified with propanohydroxamic acid groups and salicylhydroxamic acid is described. Sorption of 13 metal ions is studied as a function of pH. The composition of the sorbed complexes is determined and the apparent stability constants of the complexes in the sorbent phase are calculated. A correlation between the stabilities of the complexes in the sorbent phase and in aqueous solution is observed in some cases. Some analytical applications of the sorbents are demonstrated: trace amounts of elements can be concentrated from large volumes; molybdenum(VI) and zirconium(IV) can be separated from 10 4 -fold amounts of accompanying elements, and vanadium(V) can be determined in the sorbent phase by using diffuse reflection and photoacoustic spectrometric techniques.

Complex formation of ruthenium(IV) and osmium(VIII) with 1,10-phenanthroline on the surface of silica sorbents

Abstract A study was made of the sorption of ruthenium(IV) and osmium(VIII) by silica and silica with chemically grafted sulpho groups from solutions containing 1,10-phenanthroline. Using diffuse reflection, luminescence and x-ray photoelectron spectroscopic methods, it was found that during sorption at pH 6–7 and room temperature on the surface of silica sorbents phenanthrolinate complexes of various composition are formed, bis- and tris(1,10-phenanthroline)metal (II, III), the Os(II) to Os(III) mole ratio being 2:1. A quantitative yield of tris(1,10-phenanthroline)metal(II) complex is obtained at 98 /+- 2 °C. The rate of complex formation on the surface of the sorbents considerably exceeds the rate of formation of the corresponding complexes in solution. It is suggested that silica sorbents have a catalytic action on the process of formation of complexes of ruthenium and osmium with 1,10-phenanthroline on the sorbent surface. A rapid sorption-luminescence method for determining ruthenium and osmium is proposed. The detection limit is 7 × 10 −4 μg ml −1 for ruthenium and 1 × 10 −3 μg ml −1 for osmium.

Sorption-spectrometric determination of Copper, Mercury, and Amines using chemically modified Silica

Color reactions of copper(II) with 4-(2-pyridylazo)-resorcinol and Picramine E on silica chemically modified with iminodiacetic acid groups and the exchange reaction of mercury(II) with copper diethyldithiocarbamate in the phase of silica chemically modified with hexadecyl groups were studied. Test methods were developed for the determination of copper and mercury. It was demonstrated that long-chain amines can be determined as ion pairs with the reduced form of molybdosilicic acid at the surface of silica chemically modified with hexadecyl groups.