Extraction chromatography–electrodeposition (EC–ED) process to recover palladium from high-level liquid waste

摘要

The extraction chromatography–electrodeposi-tion (EC–ED) process was proposed for the quantitative recovery of palladium from high-level liquid waste (HLLW) in this study. The process coupled the extraction chromatography method to obtain the decontamination of Pd(Ⅱ) from HLLW with the electrochemical method to recover metallic palladium from the concentrated solution. Separation of Pd(Ⅱ) from a nitric acid medium by extrac-tion chromatography using isoBu-BTP/SiO2-P adsorbent and the electrochemical behavior of Pd(Ⅱ) in nitric acid solution in the presence of thiourea (TU) were investigated. isoBu-BTP/SiO2-P exhibited a high selectivity for Pd(Ⅱ) over other fission products (FPs), and Pd(Ⅱ) could be desorbed by TU from loaded BTP/SiO2-P. The adsorbent performed good stability against HNO3 because the adsorption performance kept Pd(Ⅱ) after extended contact with HNO3 solution. The column experiment achieved the separation of Pd(Ⅱ) from simulated HLLW successfully. The electrochemical behavior of Pd(Ⅱ) in palladium des-orption solution containing TU and nitric acid was inves-tigated at a platinum electrode by cyclic voltammetry. A weak reduction wave at-0.4 V was due to the reduction in Pd(Ⅱ) to Pd(0), and the deposition process was irreversible. In electrowinning experiments, a maximum of 92％palladium could be obtained.