Adsorption behavior of ²⁴¹Am(III) and Eu(III) by silica/polymer-based isoHex-BTP adsorbent from nitric acid solution

The adsorption behavior of ²⁴¹Am(III) and Eu(III) by silica/polymer-based isoHex-BTP adsorbent (isoHex-BTP/SiO₂-P) was investigated by a batch experiment method. isoHex-BTP/SiO₂-P exhibited high affinity and selectivity for ²⁴¹Am(III) over ¹⁵²Eu(III) in 2-4 mol/dm³ nitric acid solutions. Within the experimental contact time range of 0.5-24 h, isoHex-BTP/SiO₂-P showed high selectivity for ²⁴¹Am(III) compared to ¹⁵²Eu(III) in 3 mol/dm³ nitric acid solution. However, the adsorption kinetics of ²⁴¹Am(III) and ¹⁵²Eu(III) was slow. Eu(III) adsorption followed the pseudo-second-order kinetic model, indicating chemical adsorption as the rate-limiting step of the adsorption process. And the adsorption agreed well with the Langmuir adsorption model at various temperatures. The adsorption kinetics and isotherm data indicated that the equilibrium adsorption capacity, the adsorption rate, the maximum adsorption capacity and the adsorption affinity, increased with temperature. The thermodynamic parameters, negative change in Gibbs free energy, and positive change in enthalpy and entropy, suggested that the adsorption of Eu(III) was spontaneous and endothermic process with an increase of entropy. (authors)