Ferrous Oxidation Catalyzed by Oxy-Nitrogen Species (NOX)

Abstract

The effect of small concentrations of nitrite (4.5 mM) on 0.1 M ferrous sulfate oxidation in a 1 M sulfuric acid under 4 atm oxygen pressure at 25, 60 and 80 ºC was investigated. A mathematical model for reaction was developed and COMSOL software was used to simulate the concentration versus time trajectories in parallel with previous thermodynamic and kinetics investigations on related systems. The simulations and experiments revealed that nitrous acid disproportionates to produce N₂O₃, NO and NO₂ and subsequently, these oxy-nitrogen species are all oxidized to N(V). The oxidation rate of ferrous at higher temperatures with nitrite was 32 times faster compared to that with only oxygen present. The activation energy for ferrous oxidation was found to be 34.51 kJ mol^-1. It is expected to identify the key reaction pathways involved in leaching processes including NOx by avoiding much of the expensive Edisonian experimentation that slows innovation.