熔融燐酸塩中での遷移金属の酸化還元平衡と酸塩基性
1975 年 83 巻 958 号 p. 287-293
詳細
1975 年 83 巻 958 号 p. 287-293
The redox equilibria of transition metals (V, Fe, Cr, and Ce) in phosphate melts (Li2O-P2O5, Na2O-P2O5, K2O-P2O5, and NaPO3-Ca(PO3)2) were investigated at 900 or 1000°C.
Using the oxygen ion activity obtained by an oxygen electrode method, the dependence of the redox equilibria of transition metals on oxygen ion activity was analysed. The same procedure of analysis was applied to the redox equilibrium in sodium silicate melt.
It was shown that with exception of chromium, the redox reactions are represented by the following:
ROa(m+n-2a)+=ROa-h(m+2h-2a)++(h-n/2)O2-+n/4O2
where R is transition metal, a and (a-h) are the numbers of the oxygen atoms constituting the oxyions of the oxidized and reduced metals, respectively, and (m+n) and m are the valences of the oxidizep and reduced metals, respectively. The (reduced)/(oxidized) ratio decreased with the increase of oxygen ion activity in both melts. The decrease was more rapid in acidic composition than in basic region.
That is, h decreased toward zero as the basicity increased. From the fact that the order of the redox ratio about element was different between phosphates and silicate melts, it was suggested that the coordination of solvent oxyanion also effects on the redox equilibrium of transition metals besides the oxygen ion activity.
