Comparison of Cs desorption from hydrobiotite by cationic polyelectrolyte and cationic surfactant

Abstract

We report the Cs desorption behavior of cationic molecules, including a cationic surfactant, cationic polyelectrolyte, and ammonium ion, against hydrobiotite, which is composed of slightly expandable vermiculite and non-expandable biotite. The degree of ionization of polyethyleneimine (PEI) increased with decreasing pH, and the increased cationic charge under acidic conditions enhanced the desorption of Cs from hydrobiotite by ion exchange. Even though the cationic surfactant with a permanently charged quaternary ammonium head group showed less pH-dependent Cs desorption compared to PEI, the maximum Cs desorption of the cationic surfactant was lower than that of PEI. PEI showed the highest Cs desorption efficiency among the tested cationic ion exchangers, suggesting that the high cationic charge of the polyelectrolyte originating from its large number of ionizable units is effective at Cs desorption from mixed-layer clay minerals.