Thorium removal from aqueous solutions of Mexican erionite and X zeolite

Abstract

Thorium(IV) removal from aqueous solutions by erionite and X zeolite was investigated. The Th(IV) uptake at different thorium nitrate concentrations (from 0.25 to 25 mM) was evaluated. The thorium content in the aqueous solution was determined by neutron activation analysis. Th(IV) retained by zeolites was 1.7 and 3.7 meq/g for erionite and X zeolite. In order to explain the thorium sorption process in both zeolites, ion exchange mechanism was considered. It was found that thorium sorption behavior is strongly dependent of the type of zeolite, the separation factor for Mexican erionite was αTh(IV)Na(I)<1, this zeolite shows preference for Na(I) rather than for Th(IV), however, by X zeolite, αTh(IV)Na(I)~1, this value suggested an approximately ideal ion exchange behavior. The effect of pH on thorium sorption was also considered.