Adsorption and separation behavior of Pd(II) from simulated high-level liquid waste using N,N,N’,N’-tetra-2-ethylhexyl-thiodiglycolamide silica-based adsorbent

To efficiently separate Pd(II) from high-level liquid waste (HLLW), a (TEHTDGA + dodecanol)/SiO₂-P silica-based adsorbent (TEHTDGA resin) was synthesized by impregnating SiO₂-P particles with N,N,N’,N’-tetra-2-ethylhexyl-thiodiglycolamide (TEHTDGA) and dodecanol. Our experimental results indicate that TEHTDGA resin exhibits high distribution coefficients for Pd(II) at HNO₃ concentrations from 0.1 M to 5.0 M. The adsorption behavior of Pd(II) was found to quickly reach an equilibrium state, with a nearly 100% uptake ratio. Based on adsorption isotherm analyses, the experimental results for Pd(II) fit well with the Langmuir isotherm model. TEHTDGA resin was also confirmed to exhibit high adsorption capacity for Pd(II). The adsorption behavior of Pd(II) was hardly affected by temperature. In an evaluation of the amount of leaked sulfur, TEHTDGA resin demonstrated good chemical stability. The results of a chromatography separation experiment indicate that almost all the Pd(II) could be successfully separated and recovered from simulated HLLW using 0.1 M thiourea in 0.01 M HNO₃ solution as an eluent.