Precise Stepwise Recovery of Platinum Group Metals from High Level Liquid Waste

Abstract

Accurate separation and efficient recovery of Ru(III), Rh(III), and Pd(II) from highly level liquid waste (HLLW) is an good choice for clean production and sustainable development of nuclear energy. A silica-based amine-functionalized composite (dNbpy/SiO2-P) was synthesized by a simple and efficiency vacuum impregnation method. It exhibited high adsorption capacities towards Ru(III), Rh(III) and Pd(II) in 3 M HNO3 with the values of 47, 14.5, and 91.6 mg/g, respectively. In addition, dNbpy/SiO2-P showed excellent selectivity (SFPd/M = 1110) and repeatability (≥5). Interestingly, for the first time, a double-column experiment was designed to solve the separation and recovery of Ru(III), Rh(III), and Pd(II) from HLLW. Based on the different adsorption and desorption kinetics of Ru(III), Rh(III), and Pd(II), 0.1 M HNO3-0.1 M thiourea and NaClO (AR) were used to desorb Pd(II), Ru(III) and Rh(III). According to XPS and FT-IR analysis, the adsorption of Ru(III), Rh(III), and Pd(II) was coordination mechanism and required the participation of NO3- to maintain charge balance. For the first time, our pioneering work explores the specific distribution of elements within the adsorbents and the changes in valence state using depth-profiling XPS. Depth-profiling XPS results and slope analysis revealed that the complex of dNbpy and PGMs is a 1:1 coordination structure. Overall, this work fills the gap that Ru(III), Rh(III), and Pd(II) cannot be effectively separated and enriched from HLLW.

Keywords: HLLW, Ru(III), Rh(III), Pd(II), adsorption