The electrochemical generation of ferrate at pressed iron powder electrodes:: effect of various operating parameters

The effect of various parameters on the yield for the electrochemical generation of ferrate was investigated for pressed pellet iron electrodes. An optimum yield was observed for a NaOH concentration of 14-16 M of the anolyte. The rate of iron dissolution and generation of ferrate increased when the temperature of the electrochemical cell is raised from room temperature to 50 degreesC. The pressure applied to the iron powder during the formation of the pellet electrode did not have a strong influence on ferrate generation, at least in the range investigated in this work (5-8 ton/cm(2)). On the other hand, the purity, particle size and packing density of the powders are important factors in determining the current yield for ferrate generation and the maximum yield was not obtained with the smallest particles investigated ( < 10 mum). An optimum yield for ferrate generation of 60% was observed for a 2 h electrolysis. The surface of the pressed pellet iron electrode was also analyzed following the electrolysis in 14 M NaOH by X-ray diffraction and X-ray photoelectron spectroscopies. The electrogenerated ferrate was not detected at the electrode surface but the presence of various iron oxides and sodium carbonate was evidenced by these techniques. (C) 2003 Elsevier Science Ltd. All rights reserved.