Electrochemical behavior of plutonium in nitric acid media

Fallet, Alexis; Larabi-Gruet, Nathalie; Jakab-Costenoble, Sandrine; Moisy, Philippe

doi:10.1007/s10967-015-4423-8

“…Hence, the cathodic peak ( ii c ) corresponds to the superposition of PuO 2 + to Pu 4+ and Pu 4+ to Pu 3+ reduction (eq & ) and represents the direct reduction of PuO 2 + into Pu 3+ . , In addition to eq , PuO 2 + owing to its instability in 0.1 M HNO 3 , chemically disproportionate into Pu 4+ and PuO 2 2+ (eq ). In the reverse scan, the prominent anodic peak ( ii a ) corresponds to Pu 3+ to Pu 4+ oxidation (reverse of eq ) and the second marginal anodic peak ( i a ) corresponds to Pu 4+ to PuO 2 + /PuO 2 2+ oxidation and its intensity is very weak as it involves the Pu–O actinyl bond formation, which is a kinetically very slow process (reverse of eq ). For better observation of the anodic peak ( i a ), CV was recorded at a slow scan rate (25 mV s –1 ) that clearly identifies the Pu 4+ to PuO 2 + /PuO 2 2+ oxidation peak at 0.685 V (inset in Figure a). PuO 2 2 + + normale − = PuO 2 + PuO 2 + + 4 H + + normale − = Pu 4 + + 2 H 2 O Pu 4 + + normale − = Pu 3 + ...…”

Section: Resultsmentioning

confidence: 99%

“…Hence, the cathodic peak ( ii c ) corresponds to the superposition of PuO 2 + to Pu 4+ and Pu 4+ to Pu 3+ reduction (eq & ) and represents the direct reduction of PuO 2 + into Pu 3+ . , In addition to eq , PuO 2 + owing to its instability in 0.1 M HNO 3 , chemically disproportionate into Pu 4+ and PuO 2 2+ (eq ). In the reverse scan, the prominent anodic peak ( ii a ) corresponds to Pu 3+ to Pu 4+ oxidation (reverse of eq ) and the second marginal anodic peak ( i a ) corresponds to Pu 4+ to PuO 2 + /PuO 2 2+ oxidation and its intensity is very weak as it involves the Pu–O actinyl bond formation, which is a kinetically very slow process (reverse of eq ). For better observation of the anodic peak ( i a ), CV was recorded at a slow scan rate (25 mV s –1 ) that clearly identifies the Pu 4+ to PuO 2 + /PuO 2 2+ oxidation peak at 0.685 V (inset in Figure a). …”

Section: Resultsmentioning

confidence: 99%

A “Two-Step” Electrochemical Approach for Recovery of Plutonium and Uranium from Aqueous Acidic Waste Solutions

Agarwal,

Gamare,

Nandi

et al. 2024

Inorg. Chem.

2

0

View full text Add to dashboard Cite

Chemical quality control of nuclear fuel, particularly the determination of Pu and U contents by chemical methods, results in analytical acidic aqueous waste solutions from which Pu and U must be recovered efficiently for the remediation of radioactive wastes. Reported methods involve several complicated steps requiring addition of chemical oxidants/reductants for valence adjustments and generation of secondary wastes, thereby making the recovery process cumbersome. Herein, we report a novel two-step electrochemical approach for Pu and U recovery from acidic aqueous waste solutions containing different metallic impurities (Fe, Cr, Mn, Cd, Al, Ni, Co, Zn, and Mg) by bulk electrolysis using a Pt gauze electrode. Pu and U are recovered from these waste solutions in a two-step process: (i) bulk electrolysis of the mixed solution at a constant potential of 0.1 V vs Ag/AgCl/3 M KCl that results in the reduction of PuO 2 2+ to Pu 3+ followed by the precipitation of Pu 3+ as K 2 (K 0.5 Pu 0.5 )(SO 4 ) 2 , which is then filtered and separated and (ii) the filtrate solution is again subjected to bulk electrolysis at a constant potential of −0.35 V vs Ag/AgCl/3 M KCl resulting in the reduction of UO 2 2+ to U 4+ . The U 4+ is then precipitated as K 2 (K 0.67 U 0.33 )(SO 4 ) 2 , which is filtered and separated, leading to a Pu-and U-free aqueous acidic waste solutions. Biamperometry shows that 97.8% and 99.1% recovery of Pu and U, respectively, is possible, and emission spectrometry confirms the purity of K 2 (K 0.5 Pu 0.5 )(SO 4 ) 2 and K 2 (K 0.67 U 0.33 )(SO 4 ) 2 . Because of its operational simplicity, potential for remote handling, and excellent extraction efficiency, the present methodology can easily replace traditional methods for the recovery of Pu and U from acidic aqueous waste solutions.

show abstract

“…Besides, electrochemistry has long be exploited as a “green” method in regulating the oxidation state of Pu. [ 4,12‐13 ] Nevertheless, the quantitative electrochemical oxidation of Pu(IV) to Pu(VI) in nitric acid solution encounters great challenge, [ 4 ] and the direct contact of the electrode with the highly corrosive and radioactive solution requires high stability of the electrode material and may generate additional waste. Therefore, searching for more efficient and environmentally benign methods to generate high valent Pu is still of great interest to help establish greener approaches for the recovery of Pu.…”

Section: Background and Originality Contentmentioning

confidence: 99%

Light‐Driven Oxidation of Pu(IV) to Pu(VI) Enables Green and Efficient Pu Recovery

Dong

¹

,

Wang

²

,

Yan

³

et al. 2021

Chin. J. Chem.

2

0

View full text Add to dashboard Cite

Main observation and conclusion Plutonium (Pu) is a key actinide in nuclear industry and is the only element in the periodic table known to date that could exist in four different oxidation states simultaneously in aqueous solution. Efficient recovery of Pu in nuclear wastes relies greatly on the precise control of its oxidation states. Herein, we introduce a light‐driven oxidation approach that could effectively oxidize Pu(IV) to Pu(VI) in acidic solutions without the addition of extra chemical oxidants. The oxidation proceeds via the reaction of Pu(IV) with the oxidative species induced by UV light irradiation. This approach can help with the separation of Pu from other metals and can be further extended to a biphasic extraction system to achieve green and efficient stripping of Pu from an organic solvent.

show abstract

“…58 Specically, in strong acidic media Pu multiple redox transitions Pu(VI)/Pu(V), Pu(VI)/Pu(IV), Pu(V)/ Pu(IV), Pu(IV)/Pu(III) overlapping in a quite narrow potential range (with formal potentials 0.9-1.2 V vs. saturated hydrogen electrode or about 0.68-0.98 V vs. different kinds of Ag/AgCl electrodes). [58][59][60][61] This overlapping can lead to the fact that on cyclic voltammograms the Pu species give wide or poorly shaped redox responses. In neutral media these processes shi to lower potentials.…”

Section: The U(vi) Moieties Uptake From the Gw And Swmentioning

confidence: 99%

“…52,54,55 In particular, due to the GO inuence this redox couple shied from 0.666 V/0.092 V to 0.605 V/0.398 V (ref. 54) while due to the PEDOT:PSS inuence the couple shied from 0.674 V/0.132 V on the bare GC electrode to 0.540 V/0.496 V. 62 If compare the known electrochemical transitions of U and Pu bearing species in different valence states [53][54][55][56][57][58][59][60][61][62] on bare and coated electrodes with positions of the redox couples of the PDA-U and PDA-Pu samples (Fig. 6) one can see that in the case of PDA the shis of these transitions along the potential axis and, therefore, specic interactions of PDA with the actinides species are signicantly stronger than in the cases of GO or PEDOT:PSS.…”

Section: The U(vi) Moieties Uptake From the Gw And Swmentioning

confidence: 99%