Removal of Selected Radionuclides and Metal Contaminants by Natural Zeolites From Liquid Effluents

Abstract

Investigations have been conducted for potential applications of two natural zeolites (clinoptilolite and chabazite) obtained from ZEOX Corporation, for removal of key radionuclides (Cs, Co and Sr) and common metals contaminants (Cu, Zn) found in active liquid waste stream from nuclear operations. The low cost and easy availability makes these zeolites attractive for a wide range of industrial applications. Experiments have been conducted in shaker flask and a 4” diameter column using dilute solutions of the selected metal ions. The shaker flask experiments provided selectivity sequence for the two zeolites. Superior sorption capacity of chabazite particles has been attributed to combination of its higher pore volume and high alumina to silica ratio. The selectivity sequence is discussed based on hydrated radius and free energy of hydration of the ions. The sorbent dosage required to achieve desired removal of the contaminants is obtained from batch experiments and compared in the column tests. The measurements in column also included hydraulic behavior of the bed of zeolite particles and slurrying out of the spent bed. The spent zeolite generated from the treatment allows stabilization of the contaminants in modified cements or ceramic formulations for long-term management of the waste.