Study on Electrochemical Synthesis of Potassium Ferrate

Study on electrochemical synthesis of potassium ferrate Hong-li Shang, Zhi-feng Tian, Wei Zhu, Shi-gang Wang, Zhong-qing Huang Institution of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400043,China Introduction Ferrate is a very powerful oxidizing agent that has been considered for several applications [1,2]. There are three methods for the preparation of ferrate (VI), namely dry oxidation, wet oxidation and electro-chemical method. A number of difficulties are associated with the previously known methods for preparing ferrate(VI) salts, including the relatively low yield rate and the instability of the ferrate(VI) chemical, and the toxicity of the byproducts generated during preparation. In this paper we reported a cost-effective electrochemical method, it very promising to produce ferrate products commercially. Synthesis A novel cast iron electrodes was in the form of a foil of dimensions 18cm×3cm.The active electrode surface area was 80cm.The electrolysis condition including, applied current density, temperature, synthesis duration, electrolyte composition and concentration was showed in charts. The electrolyte was the solution of 16NaOH. The content of ferrate( ) was determined by the chromite method. The CV cycle were performed on CHI660B electrochemical workstation (CH Instrument, Inc.) A platinum electrode was made from a smooth platinum plate with an active area of 6cm was used as a counter electrode and the reference electrode was HgO/Hg electrode. Conclusion Fig.1 clearly show a 0.055M potassium ferrate solution, containing KCl, KI, Na2PO4 and Na2SiO3 was used to investigate the effect of the coexisting ions on the ferrate stability at a constant temperature of 10°C. It was found that the ferrate ions decomposed rapidly in the initial stage and appeared to be relatively stable at low ferrate concentrations when KI and Na2SiO3 were present. Fig.2 show a influence of the temperature on the electrode corresponding to the ferrate( ) formation. Fig.3 and Fig.4 clearly show the maximum current yield, obtained after 0.5h of electrolysis, has a value of 60.7% at a current density of 10mAcm and a temperature of 35°C. A current density of 100mAcm is observed as an optimal compromise between these phenomena supporting a high synthesis rate and a high current yield. A ferrate solution about 56.8gL was obtained under the optimum conditions: 16MNaOH, J=100mAcm 35°C,electrolysis duration(2.5h),The optimal current efficiency was 48.53%. The result of this study suggested that this material is very promising to improve the yield for ferrate generation and particularly, the ferrate concentration. The coexisting ions KI, Na2SiO3 have been shown to offer a longer stability period of a ferrate solution. Reference [1]Jia-Qian Jiang, Barry Lloyd. Progress in the development and use of ferrate(VI) salt as an oxidant and coagulant for water and wastewater treatment. [J] J Water Research, 2002,36 :1397–1408. [2]S. Licht , R. Tel-Vered, L. Halperin. Direct electrochemical preparation of solid Fe(VI) ferrate, and super-iron battery compounds. Electrochem Commun. 4(2002)933. 0 0.01 0.02 0.03 0.04 0.05 0.06