Potassium persulfate

Not to be confused with potassium peroxymonosulfate.

Potassium persulfate is the inorganic compound with the formula K2S2O8. Also known as potassium peroxydisulfate or KPS, it is a white solid that is highly soluble in water. This salt is a powerful oxidant, commonly used to initiate polymerizations.

Preparation

Potassium persulfate can be prepared by electrolysis of a cold solution potassium bisulfate in sulfuric acid at a high current density.[1]

2 KHSO4 → K2S2O8 + H2

It can also be prepared by adding potassium bisulfate (KHSO4) to a solution of the more soluble salt ammonium peroxydisulfate (NH4HSO4). In principle it can be prepared by chemical oxidation of potassium sulfate using fluorine.

Uses

This salt is used to initiate polymerziation of various alkenes leading to commercially important polymers such as styrene-butadiene rubber and polytetrafluoroethylene and related materials. In solution, the dianion dissociates to give radicals:[2]

[O3SO-OSO3]2- ${\displaystyle {\overrightarrow {\leftarrow }}}$ 2 [SO4]-

It is used in organic chemistry as an oxidizing agent,[3] for instance in the Elbs persulfate oxidation of phenols.

As a strong bleaching agent, it is used in hair dye substances as whitening agent with hydrogen peroxide.