Sorption of gadolinium on acid-modified clinoptilolite

Abstract

The sorptive properties of the acid-modified Transcarpathian clinoptilolite towards Gd(III) under dynamic conditions were investigated. The sorption capacity of the clinoptilolite in H-form depends on the nature and concentration of acid-modifier. The most effective sorption of Gd(III) was observed when clinoptilolite was pretreated with 1 M H2SO4 solution. The sorption capacity of the H-form of Transcarpathian clinoptilolite towards Gd(III) significantly depends on the concentration of gadolinium salt, the pH of solution and the temperature of the preliminary calcination of the sorbent. The sorption capacity of H-clinoptilolite under optimal conditions (diameter of zeolite grains was 0.20-0.31 mm; flow rate of gadolinium(III) solution with concentration 0.5 µg/mL through sorbent was 5 mL/min; and pH 10.0) was 8.2 mg gadolinium per 1 g of acid-modified clinoptilolite. The H-clinoptilolite sorbs the Gd(III) trace amounts even in the presence of other common ions. The solutions of 1 M HCl and 1 M KCl acidified by a hydrochloric acid to pH 4.0 are the most effective desorbents of gadolinium(III) ions from H-clinoptilolite. The method for gadolinium trace amounts preconcentration from aqueous solutions in a solid phase extraction mode with a further determination of this rare earth element by a spectrophotometric method was developed. The detection limit of this method is 0.3 ng/mL, and the linearity was evaluated in the range of 1-200 ng/mL.