10 Fe3O4 + 2 KMnO4 + 48 H2SO4 → 15 Fe2(SO4)3 + 2 MnSO4 + K2SO4 + 48 H2O
This is an acid-base reaction (neutralization): Fe3O4 is a base, H2SO4 is an acid.
This is an oxidation-reduction (redox) reaction:
2 MnVII + 10 e- → 2 MnII (reduction)
30 Fe8/3 - 10 e- → 30 FeIII (oxidation)
KMnO4 is an oxidizing agent, Fe3O4 is a reducing agent.