Speciation of Ruthenium in Organic TBP/TPH Organic Phases: A Study about Acidity of Nitric Solutions

Kinetic and Thermodynamic Requirements To Extend Solvent Compatibility in Thermal-Assisted Extraction of Inert Platinum Group Metals

“…To explain the difference found in the different extraction systems of Figure , we should consider the mechanistic aspects of this extraction chemistry. While the coordination chemistry of Ru 3+ in HNO 3 (aq) is quite complicated, , Ru­(III) is postulated to be present as a nitrosyl species like Ru­(NO) 3+ . Considering that TBPDA is noncharged, the positive charge of Ru­(NO) 3+ remains unchanged even after the complexation with TBPDA through the extraction regardless of its stoichiometry.…”

Complexation–Distribution Separated Solvent Extraction Process Designed for Rapid and Efficient Recovery of Inert Platinum Group Metals

“…Our next concern is to clarify the extraction mechanisms of the inert PGMs in the studied systems. Although the coordination chemistry of Ru 3+ in HNO 3 (aq) is quite complicated, 19 , 20 a Ru(III) species is believed to be present as a nitrosyl species like Ru(NO) 3+ , as suggested spectroscopically in Figure 4 a. Rh(III) in an aqueous solution is believed to be present as [Rh(H 2 O) 6 ] 3+ even in the presence of 0.5 M HNO 3 . 21 …”

Identification of a chemical fingerprint linking the undeclared 2017 release of 106 Ru to advanced nuclear fuel reprocessing

“…To help refine synthetic targets amenable to the strategy proposed in Scheme 1 , we subscribe to the hypothesis that the release of 106 Ru into the environment is associated with fuel reprocessing activity. Owing to its complex chemistry and high specific activity (typically 6 to 9% of fission products) in spent nuclear fuel ( 12 – 16 ), the removal of radio-ruthenium from waste streams poses a significant challenge. While a myriad of approaches has been proposed, the vast majority center about the PUREX (plutonium–uranium extraction) process where the recovery of uranium and plutonium is accomplished by liquid extraction with an organophosphate from fuel that is digested in nitric acid ( 16 – 18 ).…”

“…Owing to its complex chemistry and high specific activity (typically 6 to 9% of fission products) in spent nuclear fuel ( 12 – 16 ), the removal of radio-ruthenium from waste streams poses a significant challenge. While a myriad of approaches has been proposed, the vast majority center about the PUREX (plutonium–uranium extraction) process where the recovery of uranium and plutonium is accomplished by liquid extraction with an organophosphate from fuel that is digested in nitric acid ( 16 – 18 ). To amplify the oxidative power of the mixture, oxidants such as ceric ammonium nitrate can be added to encourage the evolution of the volatile and highly reactive RuO 4 , which can then be driven off with carrier gas and subsequently trapped or passivated.…”

“…To this end, we had selected the polychlorinated Ru(IV) salt, (NH 4 ) 2 RuCl 6 , the Ru(III) mixture, Ru(NO)(NO 3 ) 3 (in nitric acid), and the highly insoluble allotrope to β-RuCl 3 , α-RuCl 3 . In nitric acid solution, what is denoted commercially as Ru(NO)(NO 3 ) 3 is actually a mixture of ruthenium (III/IV) complexes varying in proportion of coordinated and exchangeable nitrate, nitrite, and water molecules, depending on solution conditions (16,43); moreover, it is directly representative of the nitric acid-based oxidative mixtures used to dissolve spent fuel early in the PUREX process (16,17). Subjecting these model compounds to the reaction conditions used to synthesize ttpyRuCl 3 (Materials and Methods), with the notable exception of using saturated ethanolic and aqueous ethanolic solutions of potassium chloride in the case of Ru(NO)(NO 3 ) 3 , produced no discernable trace of ttpyRuCl 3 ( (29)(30)(31) or the electrochemical reduction and metallization of uranium in spent fuel from molten alkali chloride mixtures (44)(45)(46).…”