Development of Two novel silica based symmetric triazine-ring opening N-donor ligands functional adsorbents for highly efficient separation of palladium from HNO3 solution

[Display omitted] •Two novel symmetric N-donor ligands functionalized adsorbents were prepared and systematically characterized.•They showed high selectivity and fast adsorption rate for Pd(II).•The adsorption mechanism of Pd(II) with two adsorbents is elucidated both experimentally and theoretically. The synthesis and characterization of two novel symmetric triazine-ring opening ligands CA-MP (pyridine derivative)/CA-BOPhen (1,10-phenanthroline derivative) functionalized SiO2-P (P = Polymer) adsorbents for separation of Pd(II) from HNO3 solutions are presented. SEM, N2 adsorption/desorption isotherms, TGA and EDS spectroscopy characterization results showed that CA-MP and CA-BOPhen were successfully introduced into the pores of SiO2-P carrier via physical intermolecular interactions. CA-MP@SiO2-P and CA-BOPhen@SiO2-P show high efficiency, high selectivity, extremely fast adsorption rates towards Pd(II) over 19 typical fission or corrosion products in HNO3 solution. The distribution coefficient Kd values of CA-MP@SiO2-P and CA-BOPhen@SiO2-P are up to 206.5 and 205.7 cm3/g, respectively, within 10–15 min of contact time in 0.4 M HNO3. The adsorption capacities of them to Pd(II) were determined to be 0.36 mmol/g and 0.23 mmol/g, respectively. The fast adsorption rates and high selectivity of two adsorbents towards Pd(II) were related to the formation of the highly preorganized complex [Pd(NO3)(L)]+ (L = CA-MP or CA-BOPhen). These results demonstrate that CA-MP@SiO2-P and CA-BOPhen@SiO2-P possess great potential for highly efficient removal of Pd(II) from highly active liquid waste (HLW).