Highly selective recovery of palladium by a new silica-based adsorbent functionalized with macrocyclic ligand

A new kind of silica-based adsorbent with high selectivity and efficient adsorption for palladium ion (Pd(II)) was synthesized in this study. A macrocyclic polyether isomer was modified for incorporation to the silica matrix as a ligand to realize the complexation between Pd(II) and the adsorbent. The adsorption of Pd(II) in HNO3 media was evaluated by both batch and column operations. Influences including acidity, contact time, initial metal concentration and elution conditions were detailed. From a practical viewpoint, the functionalized adsorbent was employed for the recovery of Pd(II) from the simulated high level liquid waste (HLLW) containing a large amount of interferences. Superior selectivity to Pd(II) as well as a recovery rate higher than 90% was obtained. A mechanism concerning the formation of complex ion-pair was proposed for the description of the Pd(II)-binding process. The macrocyclic ligand functionalized silica adsorbent possesses potential for the recovery of the palladium resource in radioactive liquid waste. (C) 2012 Elsevier B.V. All rights reserved.