| The mechanism and promotion effects of K+ on the yield of Fe(Ⅵ) were studied during the reaction of forming ferrate. The experiment results showed that K+ is far better than Na+ for the preparation of Fe(Ⅵ) at temperatures higher than 50℃. The optimal temperature for the preparation of Fe(Ⅵ) with K+ is 65℃. During the reaction, the yield of ferrate increases with the concentration of K+, and the promotion effect of K+ is obviously with ferric nitrate dosage increase. The Fe(Ⅵ) concentration prepared with 4.4 mol/L KOH is 0.05 mol/L at 85 g/L ferric nitrate; and which achieves 0.15 mol/L when added 2 mol/L K+ . The promotion effect of K+ on the yield of ferrate is remarkable when ferric nitrate dosage is higher than 75 g/L, reaction temperature is below 55℃ and ClO- concentration is lower than 1.16 mol/L. The K+ can substitute for partly alkalinity and reduce the concentration of OH- in the reaction solution. During the reaction, the K+ can enwrap around FeO2-4 that can reduce the contact between Fe3+ and FeO2-4, and decrease the catalysis effect of Fe3+ on FeO2-4. At the same time, K+ can react with FeO2-4 to form solid K2FeO4, which will lower the Fe(Ⅵ) concentration, decrease the decomposition rate of Fe(Ⅵ), enhance the stability and improve the yield of Fe(Ⅵ). |
