Research On The Electrochemical Generation Of Ferrate(Ⅵ) And The Electrochemical Property Of Ferrate(Ⅵ)

In the thesis, the technique, using porous magnetite to replace metal iron which was commonly used, as the anodic material for preparing ferrate(VI), was studied. The porous magnetite anode was anodic oxidized in a membrane electrolysis cell, with a kind of compound electrolyte containing concentrated potassium hydroxide or sodium hydroxide alkaline solution and stabilizing agent M as additive. The effect of the technique parameters, such as anode surface structure, composition of the electrolyte, cell temperature, anodic current density and duration of electrolysis, upon the anodic current efficiency for ferrate(VI) formation were systematically studied. In addition, the effect of cathodic additive for improving the discharging capacity of alkaline super- iron batteries was also studied. The main conclusions follow as below:(1) The application of porous magnetite electrode increases current efficiency for producing ferrate(VI). At T=25C, in 16 M NaOH for 5h electrolysis, the current efficiency at porous magnetite electrode was 25%. Under the same conditions, the current efficiency at slab magnetite electrode was 13.8%.(2) On the same conditions, the current efficiency for producing ferrate(VI) was higher in NaOH than in KOH with the ratio from 8 to 10. For NaOH electrolyte, The current efficiency for producing ferrate (VI) firstly increased, then decreased with the increment of alkaline concentration. And a maximum current efficiency (about 49%) was obtained at 14 and 16M NaOH. An abrupt decrease in current efficiency was observed upon increasing the NaOH concentration to 18M.(3) The application of stabilizing agent improves the stability of ferrate and the current efficiency for producing ferrate (VI). However, the mechanics of stabilizing agent is still unknown and the further study should go on.(4) Increasing the cell temperature results in faster rates of ferrate (VI) generation and higher current efficiency. However, in NaOH electrolyte this trend was diminished orreversed for temperature higher than 30C, resulting in a maximum at 30C. In KOH electrolyte, a maximum current efficiency was observed at 65 C.(5) A current density of 3.3mA.cm-2 was observed as an optimal compromise between these phenomena supporting a high synthesis rate and a high current efficiency.(6) The effect of Carbon based cathode conductive additive and stabilizing agent on super-iron batteries were studied. High super-iron battery discharge characteristics were exhibited by lum graphite as added conductors. In addition, stabilizing agent increased the use ratio of ferrate (VI) and the specific capacity of super-iron battery by 68%.