Effect of humic acid, fulvic acid, pH and temperature on the sorption-desorption of Th(IV) on attapulgite

Sorption of Th(IV) on attapulgite as a function of pH and temperature in the presence and absence of humic acid and fulvic acid was studied under ambient conditions using batch technique. The results indicated that sorption of Th(IV) on attapulgite was strongly affected by pH values. The presence of humic acid and fulvic acid enhanced the sorption of Th(IV) at low pH values and no significant influence was observed at high pH values. Sorption of Th(IV) was mainly dominated by surface complexation. Sorption of Th(IV) increased with increasing temperature of the system. Enthalpy (Delta H-0), entropy (Delta S-0) and Gibbs free energy (Delta G(0)) were calculated from the temperature dependent sorption data, and the results indicated that the sorption of Th(IV) on attapulgite was a spontaneous process. The results of sorption and desorption of Th(IV) on HS bound attapulgite indicated that the sorption of Th(IV) on HS-attapulgite hybrids was reversible.