%A"Koltunov, V S" %A"Marchenko, V I" %D1976 %I; %2 %J[] %K38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY, IRON, OXIDATION, CATALYSTS, CHEMICAL REACTION KINETICS, EQUATIONS, NEPTUNIUM NITRATES, NITRIC ACID, PERSULFATES, QUANTITY RATIO, TEMPERATURE DEPENDENCE, ACTINIDE COMPOUNDS, CHEMICAL REACTIONS, ELEMENTS, HYDROGEN COMPOUNDS, INORGANIC ACIDS, KINETICS, METALS, NEPTUNIUM COMPOUNDS, NITRATES, NITROGEN COMPOUNDS, OXYGEN COMPOUNDS, REACTION KINETICS, SULFUR COMPOUNDS, TRANSITION ELEMENTS, TRANSURANIUM COMPOUNDS, 400702* - Radiochemistry & Nuclear Chemistry- Properties of Radioactive Materials %PMedium: X; Size: Pages: 270-275 %TKinetics of Np(4) oxidation reaction by persulphate in nitric acid solution in the presence of ferric ions as catalyst %XThe kinetics of the reaction Np(IV) + Fe(III) = Np(V) + Fe(II)was investigated by a spectrophotometric method according to observation of the consumption of Np(IV) at 720 nm in a solution of HNO/sub 3/ + NaNO/sub 3/ in the concentration range; (F(III))equal (5.12-102.4).10/sup -3/ M, (H+) equal 0.14-1 M, (NO/sub 3//sup -/) = 0.5-2 M at an ionic strength of the solution ..mu.. = 0.2-2 and temperatures of 25-46/sup 0/C. To exclude the reverse reaction, (3-6).10/sup -2/ M (NH/sub 4/)/sub 2/S/sub 2/O/sub 8/, which rapidly oxidizes Fe(II), was added to the solution. The possible oxidation of Np(V) to Np(VI) was prevented by the addition of small quantities of N/sub 2/H/sub 4/. It was shown that the reaction rate is described by the equation -d(Np(IV))/dt=k(Np(IV))(Fe(III))/(H/sup +/)/sup 3/. where k = 0.490 +- 0.026 M/sup 2/.min/sup -1/ at 25/sup 0/ and ..mu.. = 1. The No/sub 3//sup -/ ions inhibit the reaction in the interval (NO/sub 3//sup -/) = 0-1 M and do not influence it at (NO/sub 3//sup -/) > 1 M. On the basis of an investigation of the dependence of k on the temperature, the energy (E = 32.5 kcal/mole), free energy (..delta..F* = 20.3 kcal/mole), and entropy (..delta..S* = 39 entropy units) of activation of the reaction were calculated. The reaction mechanism is discussed. %0Journal Article %N;Journal ID: CODEN: RADKA %1 %CUSSR %Rhttps://doi.org/ Journal ID: CODEN: RADKA INIS %GRussian