Neutron irradiation was carried out on 0.2, 0.4 and 0.7 J.lf solutions of potassium hexncyanoferrate(II) at the pH range of 2-10. Fe(CN)s'-was found when pH, it was found that the formation of Fe(OH), was time-dependent, that is, the deposition .. slowed down on passage of time after irradiation, and most of the nFe were concentrated on this fraction. We were interested in observing the formation of hydroxide in the rather undisturbed circumstances in solutions and the correlation of their yields with the radiochemical yields. In order to compare with those observed in the solids, it was felt useful to study in the concentrated solutions rather than in dilute solutions, which are normally employed in the gamma radiolysis studies. Such attempts of cause bring complexity due to the radiolytic decomposition of water. In this context the study on the neutron irradiation of potassium hexacyanoferrate(II) solutions at higher concentrations, namely, 0.2, 0.4, and 0.7M at the pH range of 2-10 will be reported.
EXPERIMENTALSolutions of K,Fe (CN)••3H JO in '0.2, 0.4, and 0.7Atl concentrations at desired pH values ranging from pH 2 to 11, adjusted either by sulfuric acid or sodium hydroxide, were prepared fresh each time and sealed in polyethylene tubes. Irradiation of the samples were carried out in the pneumatic tube of the THOR for 1, 5, and 7 hours. Chemical separations'? were carried .out 100 hours after the irradiation in each case and all of the chemical treatments were controlled at the same conditions as far as possible and at the same time schedule to eliminate any change due to the timedependent reactions.
RESULTSWhen solutions were irradiated, the pH values increased due to the hydrolysis of
The neutron irradiated potassium hexacyanoferrate(III) solutions were analyzed for Fe(CN)a'-, Fe(CN)G 3 -, and Prussian blue. The retention values (1.1%) were constant throughout the pH and concentration ranges studied, and dld not change with the length of irradia.tion. The complex. behavior of the radiochemical yield of the Fe(CN)a'-and Prussian blue was attributed to the competition of the various reactions involved in the irradiation.
MOsshauer spectra of irradiated K,Fe{CN)o, observed 3 weeks after irradiation, showed that 3% of iron was converted to Fe(CN)1I 4 -, while chemical analysis performed 100 hours after irradiation showed' 1896 was reduced to Fe(CN~'-. Prussian blue was isolated in the chemical analysis, but not observed in the MOsebauer spectra. The Prllssian blue formation was found to be time dependent.In the previous report'>, the Mosebauer and the radiochemical data were correlated for hexacyanoferrate(II), which was Dot converted into hexacyanoferrate(m) under irradiation due to the stable tf" configuration of iron. In this context, we will report the results on hexacyanoferrate(III). EXPERDIENTALAll of the experimental procedures were the same as that described previously,'? RESULTS AND DISCUSSIONThe IS value of potassium hexacyanoferrate(llI) is 0.12mm/sec with respect to sodium nitrosylpentacyanoferrate(II) dihydrate, compared to 0.20 mm/sec for potassium hexacyanoferrate(II). While hexacyanoferrate(II) is a singlet, the hexacyanoferrate(III) shows a quadrupole splitting of 0.43 mmfsec, as is shown in Fig. lao The splitting becomes sharper when the solid is brought into solution (Fig. lb), without changing Mi5ssbauer parameters. The apparent difference in the spectral shape comes from the fact that solid samples are consisted of different crystal aggregates whereas discrete ions are concerned in the solutions. Such line-narrowing in solution was also experienced in hexacyanoferratetll)'>, In general, the FWHM decreases about 10% in solutions or ion exchange resins'), Since the IS of hexacyanoferrate(II) and (III) are quite close, the resolution of Fe(CN).4-in the irradiated Fe(CN).'-was extremely difficult, especially when the content of Fe(il) was low. In the following spectral
M&sbauer spectra of K.Fe(CN)e and K.Fe(CN)e·3H zO. observed 3 weeks after irradiation, did not differ from the unirradiated samples, which implied that there was no change in oxidation state of iron. The fresh aqueous solutions of these irradiated samples also did not show any change in the oxidation state. Fe(OH), separated in chemical treatment was time dependent and was further influenced by the chemical reagents.
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