Synthetic saponite clays as promising solids for lanthanide ion recovery

Extraction of lanthanide ions with different ionic radius (La³⁺, Gd³⁺ and Lu³⁺) from aqueous solutions was carried out by using two synthetic saponite clays. The clays, prepared through a simple and low-cost hydrothermal approach, showed different particle size and cation-exchange capacity (CEC) and were characterized in order to evaluate the influence of their physico-chemical properties on the uptake process. Metal uptake tests, performed in pure water and simulated freshwater and seawater solutions, demonstrated that synthetic saponites have a general good sorption capacity with high lanthanide capture after a few hours of contact. The solid samples showed a higher selectivity for Lu³⁺, due to its small ionic radius.