Adsorption of Th(IV) onto Al-pillared rectorite: Effect of pH, ionic strength, temperature, soil humic acid and fulvic acid

The adsorption of Th(IV) onto Al-pillared rectorite as a function of rectorite concentration, Th concentration, pH, ionic strength, temperature, soil humic acid (HA) and fulvic acid (FA) was studied by using batch technique under ambient condition. The results indicated that the adsorption of Th(IV) onto Al-pillared rectorite strongly depended on pH and ionic strength, and the adsorption of Th(IV) increased with increasing Al-pillared rectorite concentration. The presence of HA/FA enhanced Th(IV) adsorption at low pH and reduced Th(IV) adsorption at high pH. The adsorption of Th(IV) decreased with increasing temperature, indicating that the adsorption process of Th(IV) onto Al-pillared rectorite was exothermic. The experimental data of Th(IV) adsorption were analyzed with the Freundlich and Langmuir models, showing that the Freundlich model fitted the adsorption data better than the Langmuir model. The adsorption of Th(IV) on Al-pillared rectorite may be dominated by surface complexation and cation exchange also contributed partly to Th(IV) adsorption. (C) 2007 Elsevier B.V. All rights reserved.