Study On Stability And Prepraration Of Potassium Ferrate(Ⅵ)

Potassium ferrate, a new multifunctional material, has been used as watertreatment agent, oxidation agent and positive active material, therefore it is apromising material. But the high cost and low stability in aqueous solution andshort-term preservation limits industrialized production. In order to overcome itsshortcomings, a series of investigation was carried on.The iron source usually used in preparing potassium ferrate is dissolubilityferric salt, such as iron nitrate, iron chlorate, iron sulfate and so on. FeOOHprepared by low-cost ferrous sulfate was used to synthesis high-purity potassiumferrate.The influence of pH value of solution, the dosage of catalyzer, reactiontemperature, reaction time, concentration of ferrous sulfate and airflow rate onthe yield of FeOOH was investigated. The yield of FeOOH was 90% (the higestyield of FeOOH is reported as 60% in literature) and the reaction time was 5h(the shortest reaction time of FeOOH is reported as 8h in literature) under theoptimal reaction conditions.The influence of mole rate NaOH and FeOOH, reaction temperature, reaction time, the dosage of alkali, the concentration of alkali, recrystallizationtemperature and the dose of addition agents on preparetion of potassium ferratewas investigated. The purity of potassium ferrate was 98% and the yield ofpotassium ferrate was 57% under the optimal reaction conditions. The thermaldecomposition product of potassium ferrate was characterized by TG-DTAanalysis. The results showed that the decomposition product of potassium ferratewas mixture of Fe⁴⁺ and Fe⁵⁺.The EDTA method and chromite method, used to test potassium ferrate,was compared and improved. And the improved chromite method was used totest the concentration of potassium ferrate solution.The factors influencing the stablility of potassium ferrate were studied. Theexperiment results showed that:1. The stability of potassium ferrate increasd with the alkali concentrationevidently (the potassium ferrate in 2mol/L KOH solution almostly decomposedentirely in 6h, but it decomposed only 9.2% in 8mol/L KOH solution in thesame time).2. The higher the purity of potassium ferrate, the higher the stability.3. FeOOH and Fe(OH)₃ could accelerated the decomposition of potassiumferrate, but the influence of FeOOH on decomposition of potassium ferrate isweaker, and potassium ferrate prepared by FeOOH had higher stability; Na₂SiO₃improved the stability of potassium ferrate evidently, however, KIO₃ was notbeneficial to the stability of potassium ferrate.