7 K2S2O8 (aq) + 2 Mn (s) + 8 H2O (l) → 2 KMnO4 (aq) + 6 K2SO4 (aq) + 8 H2SO4 (aq)
This is an oxidation-reduction (redox) reaction:
2 Mn0 - 14 e- → 2 MnVII (oxidation)
14 SVII + 14 e- → 14 SVI (reduction)
Mn is a reducing agent, K2S2O8 is an oxidizing agent.