Amberlite XAD-16 functionalized with 2-acetyl pyridine group for the solid phase extraction and recovery of palladium from high level waste solution

► AP-XAD 16 resin has shown high extractability and selectivity for palladium. ► Kinetics of extraction is fast, sorption equilibrium being attained within 30min. ► Back extraction of palladium can be effectively achieved with acidic thiourea solution. Amberlite XAD-16 has been functionalized with 2-acteyl pyridine by coupling it with 2-chloro pyridine after acetylation. The resulting resin (AP-XAD 16) has been characterized by various techniques like FT-IR, TGA, elemental analysis, etc. and has been evaluated for the solid phase extraction of palladium and other metal ions present in high level waste (HLW) solution. Sorption equilibrium was attained within 30–45min. The pseudo-second order kinetics model yielded the best fit for the experimental data of sorption kinetics. Pd sorption was found to decrease gradually with increase in aqueous phase acidity. The sorption process involves the complex formation between Pd(II) and the resin which contains the carbonyl group and soft ‘N’ atom of pyridine moiety with lone pair of electrons. The loaded palladium can be effectively eluted using acidic thiourea solutions. The adsorption isotherm data fitted well with Langmuir as well as Freundlich models. The maximum sorption capacity of the resin was found to be 8mg/g which is in agreement with the equilibrium adsorption capacity. Sorption studies carried out with simulated high level waste solution have shown very high uptake of palladium as compared to the other elements, thus showing the potential for possible use of the resin for efficient separation and recovery of palladium from HLW solution.