Impact of environmental conditions on the sorption behavior of UO2 2+ onto attapulgite studied by batch experiments

Abstract

The sorption of UO2 2+ from aqueous solution on attapulgite was investigated as a function of contact time, solid content, pH, ionic strength, foreign ions, humic acid (HA), and fulvic acid (FA) under ambient conditions by using batch technique. The attapulgite sample was characterized by XRD and FTIR in detail. The results indicated that the sorption of UO2 2+ was strongly dependent on pH and ionic strength. The sorption of UO2 2+ on attapulgite increased quickly with rising pH at pH 6.5. The presence of HA or FA enhanced the sorption of UO2 2+ on attapulgite obviously at low pH because of the strong complexation of surface adsorbed HA/FA with UO2 2+ on attapulgite surface. Sorption of UO2 2+ on attapulgite was mainly dominated by ion-exchange or outer-sphere surface complexation at low pH values, but by inner-sphere surface complexation at high pH values. The results indicate that attapulgite is a very suitable adsorbent for the preconcentration and solidification of UO2 2+ from large volumes of aqueous solutions because of its negative surface charge and large surface areas.