Electrochemical Synthesis Of K₂FeO₄ And The Analysis Of Influence Factors

The preparation and application of ferrate(Ⅵ) compounds, which could be used as strong oxidants in water treatment and organic synthesis, and cathodic materials in"super-iron"batteries, have got much attention in the world,due to their high redox potentials,large theoretic capacity, abundance of raw materials in nature and non-toxicity to the environment.In the main three preparation methods of ferrate(Ⅵ), the electrochemical preparation is widely investigated recently, due to its simple processe and non-pollution. However , the problem is that current efficiency of ferrate(Ⅵ) electrosynthesis is not very high.In this dissertation, the preparation and the purity analysis , the physicochemical properties of ferrate(Ⅵ),and the electrochemical behavior of iron electrode in alkaline solutions, In this dissertation, the influences of different additives, additive concentration and additive mixed proportion. showed the optimum concentration of Na2SiO3/KIO3 was 5mM,and the optimum concentration of KI was 2.5mM . The optimum mixed proportion was 1:1:1 the maximum current efficiency , obtained after 0.5h of electrolysis, was a value of 82.5%.As well as ,the influences of different radio of Na+/(Na++K+)([OH-]=16M) on the direct electrosynthesis solid K2FeO4 were also investigated. The results showed that, at lower temperatures(60℃), the apparent curruent efficiency of electrosynthesis solid potassium ferrate(Ⅵ) could reach 45%. The effects of ultrasound on the direct electrosynthesis of solid K2FeO4 and the anodic behaviora of pure iron were investigated, The experimental results showed that the existence of ultrasound could decrease the formation potential of ferrate(Ⅵ).when the optimum mixed proportion was 1:1:1 the maximum current efficiency , obtained after 0.5h of electrolysis, was a value of 74.3%. after 6h of electrolysis, the concentration of Na2FeO4 is 55.21g/L. but, ultrasound is no process on KOH.The electrode potential effect on electrolysis time was studied by electrochemical chronopotentionmetry (CP) methods. The surface of iron anode was smooth before electrolysis, as can be seen from scanning tunneling microscopy(STM). It became rough after 1h electrolysis, which exerted influences on electrode potential and current efficiency.In this paper the cyclic voltammograms (CVs) of iron electrode revealed a broad anodic wave between-1.40 and 0.70V versus HgO/Hg corresponding to iron dissolution and passivation of the electrode. The CV is strikingly different in that anodic wave with previous papers, where was emerging the peak which was related to the inter-mediator of electro-oxidation of Fe(III) species in concentration basic aqueous solution. It should be FeO43-(Fe(V) species). The anodic behaviour of an iron electrode in different experimental conditions was studied in this paper. The crystalline structure of the samples particles are investigated by X-ray diffraction (XRD) and Infrared absorption spectroscopy (IR).