The effect of 1-hydroxyethylenediphosphonic acid on the kinetics and the mechanism of interaction of Mn3O4 with sulfuric acid solutions

The kinetics of interaction of Mn3O4 with sulfuric acid solutions and the effect of 1-hydroxyethyl-enediphosphonic acid (H5L) on this process are studied. It is found that, as the sulfuric acid concentration is increased from 0.1 to 5 N, the rate of disproportionation of Mn3O4 to MnO2 and Mn2+ ions decreases, whereas it increases with the concentration of Mn2+ ions. Upon addition of H5L, the complete dissolution of Mn3O4 occurs more rapidly. The reaction order with respect to the H+ and H3L2- ions is equal to +0.5 ± 0.1. A mechanism of promotion of dissolution of Mn3O4 by H5L is proposed.