Quote Originally Posted by Athiril View Post
Just wondering if H2O2 can re-oxidise spent bleaches of various types, since the H2O2 would then just leave water behind (and the bleach)?
The chemical processes of Oxidatian and Reduction do not necessarily involve oxygen. Actually, they are about the transfer of electrons between atoms. An ion / molecule receiving an electron is being reduced, an ion / atom / molecule loosing an electron (and donating it to an ion being reduced), is being oxidized.

These reactions are called redox (reduction/oxidation) reactions. Never confuse them with a compulsory involvement of the element oxygen.

Wikipedia has some articles you might wish to read: