The Oxidation of Fe(II) in Acidic Sulfate Solutions with Air at Elevated Pressures. Part 2. Influence of H₂SO₄ and Fe(III)

Abstract

The oxidation of ferrous ions in acidic sulfate solutions at elevated air pressures was investigated. The effect of the Fe2+ concentration, Fe3+ concentration, H2SO4 concentration, and partial oxygen pressure on the reaction rate were determined at three different temperatures, that is, T = 90, 70, and 50 °C. A second order of reaction in Fe2+ and a first order of reaction in O2 were determined, respectively. A slight inhibition by Fe3+ on the Fe2+ oxidation reaction was observed. The reaction is first order in Fe3+ in the kinetic term for the inhibition by Fe3+. Concentrations of H2SO4 up to 1 M result in a fractional negative order of −0.6; concentrations of H2SO4 above 1 M result in a zero order. One kinetic equation for the oxidation of Fe2+ was postulated, in which the order of reaction in H2SO4 is changed depending on the H2SO4 concentration. R FE2+ = −d­[Fe2+]/dt = k[Fe2+]2 P O2 [H2SO4] c /(1 + A[Fe3+]), with c = −0.6 for [H2SO4] < 1 M, and c = 0 for [H2SO4] > 1 M. The activation energy was determined to be E A = 62.1 kJ/mol. The order c in H2SO4 is either −0.6 or zero, depending on the H2SO4 concentration.

Unraveling the SO2 Poisoning Effect over the Lifetime of MeOx (Me = Ce, Fe, Mn) Catalysts in Low-Temperature NH3-SCR: Interaction of Reaction Atmosphere with Surface Species

“…In other words, reactions ① and ② are competing processes. Besides, unstable sulfite will be rapidly oxidized to sulfates (e.g., FeSO 4 → Fe 2 (SO 4 ) 3 ), and other stable sulfates remain unchanged (e.g., Ce 2 (SO 4 ) 3 and MnSO 4 ). ,, Therefore, the deposited metal sulfate is generally referred to as Me­(SO 4 ) y ( y ≤ x ). For different metal oxides, the generation ability of surface sulfate species is also different.…”

Charge Transport Characteristics of the Passive Oxide Film Formed on 3D Printed 316 L Stainless Steel in the Presence of FeII/FeIIISpecies

“…It is known that abiotic oxidation of free Fe 2+ in acidic solutions by dissolved oxygen is kinetically slow . Similarly, it is also reported that free Fe 2+ species are less susceptible to oxidation by dissolved oxygen than Fe II -sulfate complex species . Given that oxygen was removed from the experimental system and that Fe II oxidation kinetics are slow (should oxygen diffuse into solution during the short length of an experiment), it is safe to assume that the free Fe 3+ /Fe 2+ ratio will not be affected by any in-situ homogeneous oxidation. …”

Prussian blue analog with separated active sites to catalyze water driven enhanced catalytic treatments

“…Both [Fe(CN) 6 ] 3− and [Fe(CN) 6 ] 4− react with protons to produce Fe 2+ , Fe 3+ , and HCN 45 . The Fe 2+ ions are further oxidized to Fe 3+ in an oxygen-containing environment 46 . The generated Fe 3+ substitutes the cobalt ions in the unetched compositions of Co 3+ -N ≡ C-Fe 2+ and Co 2+ -N ≡ C-Fe 2+ to form Fe 3+ -N ≡ C-Fe 2+ , causing increased NIR absorption in the frame structure.…”