Synergistic adsorption behavior of a silica-based adsorbent toward palladium, molybdenum, and zirconium from simulated high-level liquid waste

In this study, the synergistic adsorption behavior of palladium [Pd(II)], molybdenum [Mo(VI)], and zirconium [Zr(IV)] in simulated high-level liquid waste was systematically investigated based on various factors, such as the contact time, concentration of nitric acid, adsorption amount, and temperature using a silica-based adsorbent impregnated with N,N′-dimethyl-N,N′-di-n-hexyl-thiodiglycolamide (Crea) and 2, 2′, 2′ -nitrilotris[N,N-bis(2-ethylhexyl)acetamide] (TAMIA-EH). The adsorption rates of Pd(II), Mo(VI), and Zr(IV) in this synergistic adsorption system were high; thus, equilibrium states could be obtained in only 1 h with high uptake percentages of more than 90%. The adsorption abilities of Pd(II), Mo(VI), and Zr(IV) were only slightly affected by variation in the concentration of nitric acid in the range of 0.1–5 M and solution temperature in the range of 288–313 K. Selective stripping of the adsorbed Re(VII), Pd(II), Zr(IV), and Mo(VI) was successfully achieved under elution with 5 M HNO3, 0.2 M Tu (pH 1), 50 mM DTPA (pH 2), and 50 mM DTPA dissolved in 0.5 M Na2CO3 (pH 11) solutions using the chromatography method. In addition, the adsorption performance in solid-state was studied using the particle-induced X-ray emission (PIXE) method; the obtained results were in good agreement with the results obtained via column separation. [Display omitted] •Crea+TAMIA-EH showed a synergistic effect for Pd, Mo, and Zr adsorption.•The adsorption performance of Pd, Mo, and Zr was less affected by nitric acid concentration and temperature.•The selective recovery of Pd, Mo, and Zr can be achieved by Tu-HNO3, DTPA, DTPA-Na2CO3 solutions.•Adsorption behaviors in solid state were investigated by the PIXE analysis method.