Kinetics and thermodynamics of Eu(III) and U(VI) adsorption onto palygorskite

The adsorption of Eu(III) and U(VI) from aqueous solutions by palygorskite was studied by batch experiments under various experimental conditions. The palygorskite was characterized by TEM, XRD, FT-IR and potentiometric titration. The adsorption kinetics of Eu(III) and U(VI) on palygorskite were both well described by pseudo-second-order model with high correlation coefficient. The adsorption of Eu(III) and U(VI) by palygorskite decreased with increasing ionic strength, indicating outer-sphere surface complexation predominated. The adsorption isotherms indicated that the adsorption of Eu(III) and U(VI) by palygorskite fitted by Freundlich models were better than Langmuir models. The maximum adsorption capacities of Eu(III) and U(VI) on palygorskite calculated from Langmuir model were 24.26 and 46.75 mg·g− 1 at pH 4.0 and 333 K, respectively. The thermodynamic parameters suggested that the adsorption of Eu(III) and U(VI) on palygorskite was a spontaneous and endothermic process.