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.

Automated summary

TEHTDGA resin shows high adsorption capacity for Pd(II) under high HNO3 concentrations, with fast adsorption rate, high uptake ratio, temperature insensitivity, and good chemical stability. The chromatography separation experiment demonstrates successful separation and recovery of almost all Pd(II) from simulated HLLW using TEHTDGA resin with thiourea as an eluent.