Removal of 137Cs and 90Sr from actual low level radioactive waste solutions using moss as a phyto-sorbent

Moss (Funaria hygrometrica) used as phyto-sorbent, was evaluated for its potential for the removal of Cs-137 and Sr-90 from actual low level radioactive waste (LLW) solutions. Laboratory batch experiments with moss were carried out to determine optimal binding pH, exposure time and binding capacity for Cs and Sr binding. These studies indicated that sorbent showed high affinity for both Cs and Sr at pH range 5-9. Time dependence experiments showed a rapid adsorption of Cs and Sr within first 10 min of contact. Maximum sorption capacity for moss was found to be similar to6 mg/g (Cs), similar to14 mg/g (Sr) and for NaOH treated moss capacity was found to be similar to17 mg/g (Cs) and 38 mg/g (Sr). In addition desorption experiments were carried out to recover the metal ions after sorption. The presence of complementary cations Na+, K+, Ca2+, Mg2+ and Al3+ at high concentrations suppressed the sorption of Cs and Sr on treated moss. Chemical esterification experiments indicate that carboxyl groups are mainly involved in the binding of Cs and Sr from LLW solutions. These findings show that the use of moss as phyto-sorbent may be a viable alternative, for the removal of Cs and Sr from LLW solutions. (C) 2003 Elsevier B.V. All rights reserved.