Recovery of Pd from Spent Fuel: 2. Sorption Recovery of Pd from Nitric Acid Solutions on Anion-Exchange Resins

Abstract

Recovery of Pd from nitric acid solutions on various anion-exchange resins is studied. The effects of the HNO 3 concentration, temperature, and aminoacetic acid on the desorption of Pd are examined. Results of the experiments on Pd recovery from actual solutions from spent fuel reprocessing are reported.The high yield of the Pt group metals in U fission allows NPP spent fuel to be considered as a promising source of Pd and Rh, which can be widely used in various areas of engineering [1,2].After nitric acid dissolution of spent fuel, the major fraction of Pd passes into the U solution and goes to the first extraction cycle. Since Pd is poorly extracted with tributyl phosphate, after recovery of U and Pu it remains in the raffinate along with other fission products and transuranium elements.It is known that the platinum metals can be completely recovered from dilute nitric acid solutions on cation exchangers like Dowex-50 [3]. The majority of researchers believe that Pd in nitric acid solutions exists as Pd(II) in the form of [Pd(NO 3 Also Pd can be recovered from nitric acid solutions using anion exchangers bearing quaternary ammonium and tertiary amine groups, e.g., SBW, SBK, and SBU resins produced outside of Russia [5,6], and AN-31 and AV-17 resins produced in Russia [7]. Evidently, Pd is sorbed from nitric acid solutions on anion exchangers in the form of [Pd(NO 3 ) 4 ] 23 . It was demonstrated previously that, in extraction from nitric acid solutions with quaternary or tertiary ammonium nitrates, Pd is extracted as (R 4 N + ) 2 [Pd(NO 3 ) 4 ] 23 or (R 3 NH + ) 2 [Pd(NO 3 ) 4 ] 23 , respectively [8,9].In this study we determined the capacity of various anion exchangers for Pd, to elucidate their applicability to Pd recovery from NPP spent fuel. Other tasks of the study were to optimize the desorption conditions and to test the sorption process for Pd recovery with actual spent fuel solutions on a laboratory unit in a hot cell. EXPERIMENTALIn the study we used Amberlite IRA-900, Dowex 21K, and VP1-AP resins. Palladium in solutions was determined spectrophotometrically with thiourea or a-nitroso-b-naphthol.From the elution curves we estimated the distribution coefficients K d , number of column volumes to breakthrough, and dynamic exchange capacity. The breakthrough criterion was the Pd concentration in the eluate corresponding to 5% of the initial concentration. The distribution coefficient was estimated by Eqs. (1) and (2).where V b is the volume of eluate passed until reaching the concentration corresponding to 50% of the initial (cm 3 ); V f , free volume (cm 3 ); V s , volume of the sorbent bed or column volume (cm 3 ); and m, weight of air-dry sorbent (g) (K d was estimated either as a dimensionless quantity or was expressed in cm 3 per gram of sorbent). The dynamic exchange capacity (DEC) is expressed in mg Pd cm 33 of swollen sorbent or mg Pd g 33 of air-dry sorbent. This parameter was estimated as the product of K d by the initial Pd concentration. Based on the experimental dependences of K d on the so...

Recovery of Pd from Spent Fuel: 4. Precipitation of Pd from Nitric Acid Solutions with Hydrazine and CO

“…The distribution of radionuclides between the solution and Pd precipitated from the desorbate formed in sorption recovery of palladium from true HLW [10] is presented in Table 4 as an example. The solution contained 690 mg l !1 Pd, 3 M HNO 3 and 0.1 M DTPA (the specific activity per 1 mg of Pd is presented in Table 4).…”

Selective Separation of Pd(II) on Pyridine-Functionalized Graphene Oxide Prepared by Radiation-Induced Simultaneous Grafting Polymerization and Reduction

“…23,24 Strong-base polyvinylpyridine resin not only demonstrates higher adsorption capacity of Pd(II) than resins with amino groups but also has good elution yield. 23 Further studies have revealed that weak-base polyvinylpyridine resin has stronger affinity for Pd than strong-base polyvinylpyridine resin and shows high adsorption selectivity because Pd can coordinate with lone pair electrons of nitrogen on pyridine. 24 It is expected that a combination of GO and pyridine groups will realize selective separation and recovery of Pd(II).…”

“…Pyridine and its derivatives are common functional groups on ion exchange resins which exhibit high performance for the recovery of Pd­(II). , Strong-base polyvinylpyridine resin not only demonstrates higher adsorption capacity of Pd­(II) than resins with amino groups but also has good elution yield . Further studies have revealed that weak-base polyvinylpyridine resin has stronger affinity for Pd than strong-base polyvinylpyridine resin and shows high adsorption selectivity because Pd can coordinate with lone pair electrons of nitrogen on pyridine .…”

Evaluation of polybenzimidazole-based polymers for the removal of uranium, thorium and palladium from aqueous medium

“…Korolev et al . [ 38 ] compared two conventional macroporous anion exchangers, namely Dowex21 K and Amberlite IRA-900, with strong-base, macroporous vinylpyridine resin VP1-AP for the recovery of Pd from nitric acid medium. Zhang et al .…”

“…Liquid-core capsules with a non-cross-linked alginate fluid core surrounded by a gallon membrane were prepared in single step and investigated for the sorption of heavy metal ions [37]. Korolev et al [38] compared two conventional macroporous anion exchangers, namely Dowex21 K and Amberlite IRA-900, with strong-base, macroporous vinylpyridine resin VP1-AP for the recovery of Pd from nitric acid medium. Zhang et al [39] studied the recovery of palladium from simulated nuclear waste using a macroporous vinylpyridine anion-exchange resin embedded in porous silica beads and reported that the weak-base resin (SiPyR-N3) shows stronger affinity towards Pd(II) than a strong-base (SiPyR-N4) anion exchanger.…”