Equilibrium of Nitrous Acid-Catalyzed Oxidation of Neptunium in Nitric Acid-TBP Extraction System.

The redox equilibrium of neptunium with nitric and nitrous acids, NpOz++ (3/2)H++ (1/2) NOs-=Np0z2++ (1/2)HNOz+ ( 1 / 2 ) H z 0 was studied in 3 to 6 hi nitric acid solutions by 30 vo1,9,/ TBP-dodecane extraction.'I'he equilibrium distribution ratio of neptunium was shown to be expressed by D-=D,;R/(l+R), where R is [Np(VI)]/iNp(V)] and D,; the distribution ratio of pure Np(b1).T o examine the dependence of the apparent concentration constant for the reaction,on nitric acid concentration, the redox potentials of HNO,/HNOz solutions were measured which revealed that the activity correction on H.'., NO,-, HNO, and HzO was effective enough to give an ideal Nernst relationship for the potential of HNOJHNO,.With using the activity coefficient quotient, Y=-Ys2/(y,a,,)1/z (y, : stoichiometric activity coefficient of nitric acid, yU : activity coefficient of HNOI.a,, : rational activity of water), the apparent concentration constant Kapp was shown to be expressed by Kapp=ICrnixY, where Kmix= ;Np(\?)] {HNOz) l'' (HzO]l/z/~Np(\.'):l{Hi.] {NO:,-] '1' and log K,i,=-2.77 and log Y--0.13.0.02 and 0.28 for 1HN03-.L::3.4 and 6 h ~. respectively.

Перевод пока недоступен