Adsorption characteristic of Cs⁺ and Co²⁺ ions from aqueous solutions onto geological sediments of radioactive waste disposal site

Abstract

The physico-chemical characteristics of clayey (CS) and brown sand (BSS1) sediments from the host geological formation of Inshas radioactive waste disposal site were explored and were correlated with the adsorption properties toward Cs+ and Co2+. Fe2O3 and SiO2 were the two most abundant chemical compounds in both sediments with greater percentage of the former in the CS which had platy surfaces (31.51 m2/g). FT-IR analyses evidenced the comparability between the contained low quantities of organic matter in both sediments. Geochemical study was carried out to investigate the weathering history and tectonic setting taken from the site area. Batch adsorption experiments of Cs+ and Co2+ reflected greater capacities of the CS which were correlated to the occurrence of hematite, kaolinite, vermiculite and plagioclase minerals, detected by XRD. All studied adsorption systems were kinetically controlled by the chemical sorption mechanism. The sorption isotherms ordered the adsorbed amounts to the following: Cs+/CS > Cs+/BSS1 > Co2+/CS > Co2+/BSS1. Langmuir, Freundlich, Dubinin-Radushkevitch and Temkin isotherm equations were applied to specify the affinities of CS and BSS1. Values of ΔH° reflected the exothermic natures for both systems of Cs+ and vice-versa regarding Co2+. Values of ∆G° revealed that the only spontaneous systems were the Cs+/CS at 298 and 313 K. The studied sediments gave good performance toward postponing the potential release of Cs+ and Co2+ into biosphere.