Preconcentration of the Gd(III) on transcarpathian clinoptilolite

Abstract

The sorption properties of Transcarpathian clinoptilolite towards trace amounts of Gd(III) under dynamic conditions have been studied. It is demonstrated that the most effective sorption of this REE occurs from low alkaline solution (pH 9.5). The buffer solution has been used to maintain the constant value of pH, ioniс strength of the solutions and to improve the metrological characteristics of preconcentration methods of Gd. The trace amounts of Gd(III) are sorbed most effectively with borate buffer solution.The final concentration of the borate buffer in the sample solution is 4·10 –4 М. The calculation of the distribution of different forms of Gd(III) in aqueous solutions depending on pH at various values of the total concentration has been carried out. The sorption of Gd(III) is carried out mainly by means of the adsorption of soluble hydrolyzed forms of Gd(III) on the zeolite surface. The sorption capacity of clinoptilolite under optimal conditions (diameter grains of sorbent – 0.200–0.315 mm; pH 9.5; temperature of preliminary thermal treatment ~ 250 ºC; flow rate of the solution of Gd(III) with the concentration of 0.5 μg·mL –1 through the sorbent – 5 mL·min –1 ) is 6.5 μg·g –1 . The differences in sorption mechanisms and optimal conditions of Gd(III), Nd(III), Tb(III), Eu(III) give an opportunity to separate Gd(III) and these REE. The influence of the most common water ions on the preconcentration of Gd(III) on Transcarpathian clinoptilolite has been established.The most effective desorbent of Gd is a 1 М solution of KCl, acidified to рH 2.6, by means of which 100 % of Gd is desorbed from the zeolite matrix.The method for the preconcentration of trace amounts of Gd(III) from aqueous solutions in solid phase extraction modewith the following analysis of the REE by thephotometric method using arsenazo III has been proposed. Key words: sorption, preconcentracion, gadolinium, solid phase extraction, clinoptilolite.