3 FeIII2-I + 22 HNVO3 3 FeIII(NVO3)3 + 6 HIVO3 + 13 NIIO + 8 H2O

This is an oxidation-reduction (redox) reaction:

6 I-I - 36 e- 6 IV (oxidation)

13 NV + 39 e- 13 NII (reduction)

3 FeII - 3 e- 3 FeIII (oxidation)

Change the oxidation states