Adsorption of Rare Earth Elements at Modified Saponite

The authors justify theoretically and experimentally the promising modification methods for saponite—pillaring and thermal treatment. These methods ensure production of sorbents with high capacity of cation exchange relative to cations of rare earth elements. The mechanism of pillaring and thermal treatment of saponite-bearing products at the temperature of 625 °C includes expansion of the mineral layers, generation of additional acid and oxidation–reduction centers (pillaring), as well as restructuring with formation of meta stable phases (thermal treatment). Optimization of application parameters of the sorbent (pH, sorbent-to-solution ratio) ensures efficient recovery of some REE from pregnant solutions of eudialyte concentrate leaching at the adsorption capacity up to 18.8 mg/g.