Americium(III) oxidation by copper(III) periodate in nitric acid solution as compared with the action of Bi(V) compounds of sodium, lithium, and potassium

Abstract

The oxidative action of a Cu(III) periodate compound toward Am(III) in nitric acid was studied. The extent of oxidation of Am(III) to Am(VI) was investigated using a constant initial Cu(III)-to-Am(III) molar ratio of 10 : 1 and varying nitric acid concentrations from 0.25 to 3.5 mol/L. From 0.25 to 3 mol/L HNO 3 , more than 98% of the Am(III) was oxidized to Am(VI); however, at 3.5 mol/L HNO 3 , the conversion to Am(VI) was only 80%. Increasing the Cu(III)-to-Am(III) molar ratio to 20 : 1 in 3.5 mol/L HNO 3 resulted in 98% conversion to Am(VI). For comparison, oxidation of Am(III) with NaBiO 3 was studied at 3.5 mol/L HNO 3 and the same stoichiometric excess of Bi(V) oxidant over Am(III) (stoichiometric ratio of 3.33 : 1). With NaBiO 3 , the extent of Am(III) conversion to Am(VI) was only 19%, while with the Cu(III) compound this value was found to be about 4 times higher under otherwise identical conditions. Similar results were obtained with other Bi(V) salts. These results show that the Cu(III) periodate compound is a superior oxidant to NaBiO 3 , yielding rapid conversion to Am(VI) in a homogeneous acidic solution, and is, therefore, an excellent candidate for further development of Am separation systems.

Organic and Aqueous Redox Speciation of Cu(III) Periodate Oxidized Transuranium Actinides

“…Similar to NpO 2 + , the oxidation efficiency is impacted by Cu 3+ periodate reduction in the molar nitric acid media . Similar observation was made by Sinkov and Lumetta, who used a 1:10 mol ratio to oxidize Am 3+ to AmO 2 2+ with Cu 3+ periodate . Furthermore, the study showed that while >99% oxidation was achieved below 2 M HNO 3 , the efficiency decreased to 77% at 3.5 M HNO 3 .…”

“…The mass balance throughout the duration of the experiment was 100 ± 1%. It has been noted that periodate’s oxidation capacity is not strong enough to oxidize Am 3+ . ,, However, reduction of periodate to IO 3 – is strong enough to oxidize NpO 2 + to NpO 2 2+ . Reduction of Cu 3+ periodate in solution produces H 5 IO 6 which remains stable for long durations in acidic media .…”

Ultrafiltration separation of nanoscale Am(VI)-polyoxometalate clusters from lanthanides

“…In the 243 AmO2 sample, the weight ratio of 243 Am, 241 Am, 242 Am are 99.987 %, 0.012 %, and < 0.001 %, respectively. The oxidation of Am(III) to Am(VI) in aqueous solution was achieved by Cu(III) periodate oxidant according to the reported procedure 28 .…”

Oxidation and extraction of Am(VI) using a monoamidic extractant in 3D printed centrifugal contactors

“…The standard potential for the Am(III)/Am(VI) redox couple under acidic conditions is about 1.7 V, and thus strong oxidizing agents are required [1,11]. Several oxidants have been explored including peroxydisulfate [12,13], copper(III) periodate [14,15], electrochemical techniques [16], and sodium bismuthate [5][6][7][8]17]. Once oxidized the Am(VI) exists as the americyl AmO 2 2+ ion and behaves similarly to the other hexavalent actinyl cations.…”