Amberlite XAD-16 Functionalized with 2-Acetyl Amide Group for the Solid Phase Extraction and Recovery of Palladium from High Level Waste

Acetyl amide grafted XAD-16 (ACAM-XAD16) resin has been synthesized by acetylating Amber lite XAD-16 resin followed by coupling it with N,N'-diisobutyl-2-chloroacetamide. Various instrumental techniques such as FT-IR, TGA, and elemental analysis were used to characterize ACAM-XAD16 resin. The resin has been evaluated for the solid phase extraction of palladium and other metal ions present in high level waste (HLW). The sorption kinetics of Pd onto the resin was found to be fast, with equilibrium being attained within 45-60 min. The experimental data fit well with the pseudo-second-order kinetics model of sorption kinetics. With the increase in aqueous phase acidity, Pd sorption increases initially, reaches a maximum around 3.0 M and then decreases. The sorption process involves the complex formation between Pd(II) and the resin which contains the carbonyl groups from the acetyl and the amidic moieties. The loaded palladium can be effectively eluted using acidic thiourea solutions and HEDTA solutions. The isothermal adsorption data fit well with both the Langmuir and the Freundlich models with maximum sorption capacity equal to 9 mg/g, which corroborates well with the equilibrium sorption capacity. Sorption studies carried out with simulated high level waste solution have shown very high uptake of palladium and small coextraction of lanthanides compared to the other elements.