C2IIIO42- + 4 H+ + MnIVO2 (MnII)2+ + 2 CIVO2 + 2 H2O

This is an oxidation-reduction (redox) reaction:

MnIV + 2 e- MnII (reduction)

2 CIII - 2 e- 2 CIV (oxidation)

MnO2 is an oxidizing agent, C2O42- is a reducing agent.