Redox reactions of actinides in carbonate and alkaline solutions

Shilov, V. P.; Yusov, A. B.

doi:10.1070/rc2002v071n06abeh000719

Cited by 15 publications

(13 citation statements)

References 41 publications

(100 reference statements)

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“…There is general agreement that Np(VI) most probably exists in alkaline media as a centrosymmetric anion either NpO 4 (H 2 O) 2 2− or NpO 2 (OH) 4 2− [1,2]. Reported crystal structures of Np(VII) compounds are most consistent with the structurally analogous species NpO 4 (OH) 2 3− as the Np(VII) species that precipitates from alkaline solutions [5][6][7].…”

Section: Introductionmentioning

confidence: 82%

“…However, the data available in the literature on oxidation-reduction potentials and speciation are somewhat contradictory and in places are incomplete. For example, Shilov proposes that the hydroxo-complexes NpO 2 OH, NpO 2 (OH) 2 − , NpO 2 (OH) 3 2− , NpO 2 (OH) 4 3− dominate the speciation of Np(V) in basic solutions [2]. Neck, Kim and Kanellakopulos [3], on the other hand, concluded that NpO 2 OH and NpO 2 (OH) 2 − are the only important Np(V) species between pH 7 and 14.…”

Section: Introductionmentioning

confidence: 99%

“…For example, Shilov proposes that the hydroxo-complexes NpO 2 OH, NpO 2 (OH) 2 − , NpO 2 (OH) 3 2− , NpO 2 (OH) 4 3− dominate the speciation of Np(V) in basic solutions [2]. Neck, Kim and Kanellakopulos [3], on the other hand, concluded that NpO 2 OH and NpO 2 (OH) 2 − are the only important Np(V) species between pH 7 and 14. Neck, Fanghänel and Kim [4] reported the existence of mixed hydroxo-carbonate complexes of Np(V) and suggested that some previous data on Np(V) speciation in base were obtained using alkaline solutions contaminated by CO 2 .…”

Section: Introductionmentioning

confidence: 99%

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Electrochemical and spectrophotometric investigations of neptunium in alkaline media

Gelis¹,

Vanýsek²,

Jensen³

et al. 2001

Radiochimica Acta

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The results of electrochemical and spectrophotometric studies of neptunium in concentrated alkali ([OH − ] tot = 0.9 to 6.5 M) and mixed hydroxo-carbonate solutions are reported. Using cyclic voltammetry, we have demonstrated reversibility of the Np(VI)/(V) couple and quasi-reversibility of the Np(VII)/(VI) couple in basic solutions ([OH − ] tot above 1.0 M), implying nearly constant coordination geometries for the predominant Np(V), Np(VI) and Np(VII) species in such media. For the first time, formation of Np(IV) hydroxide in alkaline solutions has been demonstrated using voltammetric methods. The formal redox potential of the Np(VI)/(V) couple in 1 M NaOH was determined to be 0.106 ± 0.001 V/N.H.E. This value is different in NaOH and LiOH media, which we have interpreted to indicate a specific interaction between the lithium cation and a Np anionic species. At [CO 32− ] tot greater than 0.1 M in 1.8 M NaOH, the Np(VI)/(V) couple was found to be quasireversible while the Np(VII)/(VI) couple was irreversible. Formal redox potentials for Np in several alkaline solutions have been evaluated. These results are discussed in comparison with previously reported information.

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Section: Introductionmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electrochemical and spectrophotometric investigations of neptunium in alkaline media

Gelis¹,

Vanýsek²,

Jensen³

et al. 2001

Radiochimica Acta

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“…Za njegovu aktivaciju najčešće su potrebne visoke temperature ili oksidansi. Neki od prvih postupaka aktivacije upotrebljavali su kao katalizatore organometalne sustave, [3][4][5][6] metalne ione u plinovitom stanju 7,8 i biokemijske sustave, 9 pri čemu se aktivacija metana može provesti heterogenom, [10][11][12] ili homogenom katalizom. 13,14 Metode izravne pretvorbe dijele se na oksidacijske i neoksidacijske, ovisno o prisutnosti oksidansa.…”

Section: Izravna Pretvorba Metanaunclassified

Novi petrokemijski procesi na temelju izravne pretvorbe metana

Faraguna

Jukić

2015

Kem. Ind.

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Zavod za tehnologiju nafte i petrokemiju Fakultet kemijskog inženjerstva i tehnologije Sveučilišta u Zagrebu Marulićev trg 19, 10 000 Zagreb Sažetak Petrokemija je grana kemije i kemijskog inženjerstva koja proučava reakcije i procese dobivanja i svojstva proizvoda iz naftnih prerađevina i prirodnoga plina, a koji ne služe kao goriva ili maziva. U svojim početcima petrokemija, odnosno organska kemijska industrija, temeljila se na etinu i Reppeovim sintezama. Danas su osnovne petrokemikalije olefini i aromatski ugljikovodici, s težnjom razvoja novih procesa i sve veće uporabe sinteznog plina, metana i drugih alkana kao ishodnih sirovinskih komponenti. U ovom radu dan je pregled reakcija i novih procesa izravne pretvorbe metana u vrjednije petrokemijske proizvode. Kroz pojedina poglavlja u radu su detaljnije opisane reakcije parcijalne oksidacije metana, dehidroaromatizacije metana te oksidacijskog i neoksidacijskog spajanja metana u više ugljikovodike. Ključne riječi 28F. FARAGUNA i A. JUKIĆ: Novi petrokemijski procesi na temelju izravne pretvorbe metana, Kem. Ind. 64 (1-2) (2015) 27−37 iskoristi, teži se proizvodnji vrjednijih kemikalija na samom nalazištu.Metan je simetrična i stabilna molekula kojoj treba dovesti energiju da bi došlo do pucanja stabilne C−H veze (435 kJ mol −1 ) i daljnje reakcije za dobivanje željenog produkta. S obzirom na način dovođenja energije, reakcijski put može biti izravna (slika 1) i neizravna (slika 2) pretvorba metana u petrokemijske proizvode.Izravna pretvorba metana obuhvaća sljedeće reakcije: parcijalnu oksidaciju metana u metanol ili formaldehid, dehidroaromatizaciju metana u aromatske ugljikovodike (aromate) te oksidacijsko i neoksidacijsko spajanje metana u više ugljikovodike. Dobiveni petrokemijski proizvodi mogu se dalje prevesti u benzin, katalitičkim procesima pretvorbe metanola (engl. Methanol to Gasoline, MTG) i olefinskom oligomerizacijom viših ugljikovodika.Kod neizravne pretvorbe metana najprije se iz metana parnim reformiranjem proizvodi sintezni plin, smjesa CO i H 2 , koji je osnova za daljnju sintezu petrokemijskih proizvoda. Iz sinteznog plina Fischer-Tropschovom sintezom mogu se proizvesti alkani (parafini) i benzin, dimetil-eter, selektivnom sintezom olefini, selektivnom hidrogenacijom i oksosintezom viši alkoholi i karboksilne kiseline te metanol. Iz navedenih primarnih petrokemijskih proizvoda daljnjim reakcijama prema slici 2 mogu se proizvesti benzin i olefini iz metanola i dimetil-etera, dok se hidrokrekiranjem i hidroizomerizacijom iz parafina proizvodi benzin. Viši alkoholi i kiseline proizvode se iz metanola. Izravna pretvorba metanaRazvoj postupaka izravne pretvorbe metana od velikog je interesa jer bi se za dobivanje korisnih petrokemijskih proizvoda navedenim postupcima izbjegla uporaba energetski zahtjevnog procesa parnog reformiranja. Također bi se smanjila potreba za proizvodnjom olefina procesima parnog i katalitičkog krekiranja. Metan je kao stabilnu molekulu nepolarnog karaktera i bez funkcijskih skupina teško destabilizirati i potaknuti na ...

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“…If a solution of 2 M Na 2 CO 3 is used, Am(III) is oxidized with ozone to Am(VI) at room and lower temperatures with an accumulation of Am(V) occurring at higher temperatures. [40][41] In 0.03-0.1M KHCO 3 , Am(V) precipitates as the salt KAmO 2 CO 3 . Without a consideration of the possible complexes that can be formed with americium, the oxidation of Am(III) could be described by the following equations.…”

Section: Task 3 Am/ln Separation With Oxidation State Adjustment Andmentioning

confidence: 99%

Selective Separation of Trivalent Actinides from Lanthanides by Aqueous Processing with Introduction of Soft Donor Atoms

Nash¹,

Clark²,

Lumetta³

2009

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With increased application of MOX fuels and longer burnup times for conventional fuels, higher concentrations of the transplutonium actinides Am and Cm (and even heavier species like Bk and Cf) will be produced. The half-lives of the Am isotopes ( 241 Am, 433 yrs; 243 Am, 7370 yrs) are significantly longer than those of the most important long-lived, high specific activity lanthanides or the most common Cm, Bk and Cf isotopes, thus the greatest concern as regards long-term radiotoxicity. With the removal and transmutation of Am isotopes, radiation levels of high level wastes are reduced to near uranium mineral levels within less than 1000 years as opposed to the 10 4

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Redox reactions of actinides in carbonate and alkaline solutions

Abstract: For Abstract see ChemInform Abstract in Full Text.

Cited by 15 publications

References 41 publications

Electrochemical and spectrophotometric investigations of neptunium in alkaline media

Electrochemical and spectrophotometric investigations of neptunium in alkaline media

Novi petrokemijski procesi na temelju izravne pretvorbe metana

Selective Separation of Trivalent Actinides from Lanthanides by Aqueous Processing with Introduction of Soft Donor Atoms

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