Study of the Applicability of a Functionalized Silica-Based Adsorbent for Pd(II) Separation from Simulated High-Level Liquid Waste

Abstract

In this study, to separate Pd(II) and other metal ions from high-level liquid waste (HLLW) for the effective use of limited resources, the applicability of a functionalized silica-based adsorbent was evaluated via batch-adsorption and chromatographic separation experiments using simulated HLLW containing 15 metal ions. The functionalized silica-based adsorbents used were 3-mercaptopropyl-functionalized silica gel (MP-Si), 2,4,6-trimercaptotriazine-functionalized silica gel (DMT-Si) triaminetetraacetate, sodium salt-functionalized silica gel (TAAcONa-Si), and 3-aminopropyl-functionalized silica gel (AP-Si) with different structures. Among them, MP-Si, DMT-Si, and TAAcONa-Si showed an adsorption capacity for Pd(II). In addition, the adsorption of Pd(II) onto TAAcONa-Si had relatively high adsorption stability for HNO3 concentration and contact time. Moreover, regarding the maximum adsorption amount of Pd(II), adsorption onto MP-Si and DMT-Si with thiol had a larger amount than that of TAAcONa-Si with polydentate ligand. The adsorption of Pd(II) onto TAAcONa-Si was preferable under low-temperature conditions, indicated by thermodynamic analysis. The chromatographic results showed the complete separation of Pd(II) from simulated HLLW using TAAcONa-Si by 0.1-M thiourea–0.01-M HNO3 solution. On the basis of these results, it is possible to change metal ion selectivity using a functionalized silica-based adsorbent having a different structure, and the separation of Pd(II) and other useful metal ions from HLLW is applicable.