The sorption of UO22+ 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 UO22+ was strongly dependent on pH and ionic strength. The sorption of UO22+ on attapulgite increased quickly with rising pH at pH < 6.5, and decreased with increasing pH at pH > 6.5. The presence of
HA or FA enhanced the sorption of UO22+ on attapulgite obviously at low pH because of the strong complexation of surface adsorbed HA/FA with UO22+ on attapulgite surface. Sorption of UO22+ 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 UO22+ from large volumes of aqueous solutions because of its negative surface charge and large surface areas.