Adsorption characteristics of Eu(III) and Th(IV) ions onto modified mesoporous silica SBA-15 materials

Abstract

SBA-15 mesoporous silicas functionalized with N-propyl salicylaldimine(SBA/SA) and ethylenediaminepropylesalicylaldimine (SBA/EnSA) were prepared, characterized and employed as efficient adsorbents for solid phase extraction (adsorption) of europium(III) and thorium(IV) ions from water solutions. The effect of pH, adsorbent dosage, contact time, initial concentration, solution volume and competitive ions were investigated and discussed. Extraction process of europium and thorium ions by both of the adsorbents was shown to be pH dependent, whereas it was independent on ionic strength of the aqueous. This study revealed high performance of SBA/EnSA and SBA/SA with relatively rapid kinetics in the removal and preconcentration of europium and thorium ions from aqueous solutions. Although SBA/EnSA showed higher affinity towards the studied ions with respect to SBA/SA, both of the adsorbents showed more selective characteristics towards thorium ions. The isotherms and kinetics of the processes were well described by Langmuir and pseudo second order models, respectively. The evaluated thermodynamic parameters showed the extraction process of both of the studied metal ions by SBA/EnSA and SBA/SA was spontaneous and was controlled by positive entropy changes. The adsorbents were used for decontamination of real water samples from europium and thorium ions.