Thorium Uptake on Synthetic Inorganic Ion Exchangers

Abstract

Birnessite, antimonysilicate, and their cation-exchange derivatives were tested to take up thorium. Sorption experiments were performed in different concentrations of acid, sodium, potassium, and calcium nitrate solutions in order to evaluate the influence of cations that are likely to be present in waste effluents. Variation in the magnitude and mechanism of thorium sorption on the exchangers was ascribed to structural differences and the exchange properties of the materials, as well as the aqueous chemistry of thorium. The work included investigation of thorium solution' pH in controlling the sorption process. In acidic solutions, H-antimonysilicate proved to be the best sorbent. The structure of M-H-birnessite allows facile mobility of the interlayer cations with little structural rearrangement, making it of great importance for ion-exchange use in salt conditions. Potassium had the most, and sodium the least effect on thorium selectivity by birnessites, when they are present as macro components. Conversely, calcium ions did greatly inhibit the sorption behavior of thorium on Ca-antimonysilicate. Studying the effect of thorium solution' pH reflected the fact that the microcrystal modifications of birnessites occurred during experiments. In summary, H-birnessite showed superior uptake for thorium in comparison to other materials investigated in the literature, which reflects the characteristics of the material selectivity.