2 FeIIS2-I + 12 HNVO3 Fe2III(NIVO3)3 + 9 NIIO + 4 H2SVIO4 + 2 H2O

This is an oxidation-reduction (redox) reaction:

4 S-I - 28 e- 4 SVI (oxidation)

9 NV + 27 e- 9 NII (reduction)

3 NV + 3 e- 3 NIV (reduction)

2 FeII - 2 e- 2 FeIII (oxidation)

Change the oxidation states