Coal degradation by anodic oxidation using an electron mediator was st
udied for alkaline coal slurry. To oxidize a coal effectively with ins
ignificant oxygen generation, a suitable mediator system was sought on
the basis of experimental results of redox potential of coals and an
anode potential at which oxygen was generated. The experimental result
s showed that a redox couple Fe (CN)6(3-) + e = Fe(CN)6(4-) mediated e
ffectively electrolysis of an alkaline slurry of Taiheiyo coal and was
found to be suitable as the mediator system. To know whether or not t
he mediator system can be applied to other coals, the rate of a chemic
al reaction step involved in the anodic coal oxidation was studied for
various coals. The results showed that the rate of the chemical react
ion step decreased with higher rank coals. Thus, the present mediator
system was suggested to be efficient for relatively low rank coals.