The scavenging of UO22+ using 4-sulfonic calixarene in the presence of a strong adsorbent was studied as a function of pH. The adsorbent selected
was goethite because of its strong affinity for UO22+ and its abundance in natural soils. In order to understand the underlying chemistry of the scavenging process, the adsorption
of UO22+ and 4-sulfonic calixarene onto goethite, respectively, and the extraction of adsorbed UO22+ from goethite surface were modeled using the triple-layer model. The model well explained the pH dependence of the adsorption
and extraction processes. This work showed that maximum extraction was obtained around pH 10.5 in the presence of 12g/l goethite
in the case of a 1:3TU(VI):Tcalixareneratio.