Solubility Of Magnetite Research Articles

A calculation of gibbs free energies for ferrous ions and the solubility of magnetite in H 2O and D 2O to 300°C

Gibbs energy and entropy data for aqueous Fe 2+, FeOH +, HFeO − 2 and FeO 2− 2 are critically reviewed. The most reliable values are used in a Criss—Cobble extrapolation to calculate Gibbs energies to 300°C and, hence, the solubility of Fe 3O 4 in H 2O and D 2O as a function of the pH or pD at 25°C. A set if Gibbs energies is presented which satisfies the Criss—Cobole entropy correspondence principle and which is consistent with both the reliable low-temperature thermodynamic data and all published high-temperature solubilities.

The solubility of magnetite and hydrolysis of ferrous ion in aqueous solutions at elevated temperatures

The solubility of magnetite (Fe 3O 4) in dilute aqueous solutions saturated with H 2 at 1 atm at 25 °C has been measured at temperatures between 50 and 300 °C. The solutions have ranged from KOH of molality 400 × 10 −6 mol kg −1 to HCl of molality 100 × 10 −6 mol kg −1. The measurements were made by the continuous flow of solution over a bed of specially prepared pure magnetite. It was found that, under these conditions of temperature and hydrogen activity, Fe 3O 4 does not transform to HFe 5O 8 or γ-Fe 2O 3. The results have been fitted with a scheme of soluble species consisting of Fe 2+, FeOH +, Fe(OH) 2, and Fe(OH) 3 −, and the equilibrium constants for the reactions ( 1 3 Fe 3O 4 + (2−b)H + + 1 3 H 2(g) = Fe(OH) (2−b)+ b + 4 3 H 2O have been calculated. The temperature coefficients of the constants for Fe 2+ and FeOH + were found to be negative, and those of Fe(OH) 2 and Fe(OH) 3 −, positive. The estimated values of ΔH o and ΔS o for these reactions are also given. The value of log 10( K/mol kg −1) at 25 °C for the reaction Fe 2+ + H 2O = FeOH + + H + , has been determined by extrapolation of the solubilities and has been found to be (−9.3 ± 0.5). The solubilities have been combined with other thermodynamic data to calculate ΔG o, ΔH o, and ΔS o for the formation of Fe 2+ and FeOH + by the reaction: Fe + bH 2O + (2−b) H + = Fe(OH) (2−b)+ b + H 2(g) . The extrapolated value of ΔG o for the formation of Fe 2+ at 25 °C by this reaction gives an E o of (0.475 ± 0.010) V.

Solubility of cupric oxide in pure subcritical and supercritical water

THE DISSOLUTION, transport, and deposition of metallic oxides is an important factor in the operation of the high-pressure water circuit of modern power station boiler units. As feedwater purity improves, the relative importance of the metallic oxide impurities, which result largely from the corrosion of the water circuit containment itself, increases. A major parameter in each of the processes quoted above is the solubility of the oxide species in the high-temperature, high-pressure aqueous environment, but there is little data available for the systems of greatest practical significance, Fe304-H20, CuO-H20, and Cu20-H20. Sweeton et al. (8, 9) have studied the subcritical solubility of magnetite, Fe3O4, as a function of chloride ion concentration, while a small area of the supercritical solubility diagram for the system Fe304-H20 has been explored by Martynova (6). The measurements made by Pocock and Stewart (7) in the systems Cu-H20, Cu20-H20, and CuO-H20 were over a restricted range of pressure and temperature, and the results showed considerable scatter. In the present work, the solubility of cupric oxide, CuO, has been measured in pure water of pH 7.5 over the temperature range 50 to 550°C. and along a series of isobars between 3500 and 6000 p.s.i.g.

人工磁性酸化鉄の溶解性

One of the authors has already reported that artificial magnetite made from Fe2O3by the reduction at a temperature range 600°-800°C with a gas mixture composed of CO (10%), CO2 (90%) and SO2 (ca. 1%) was dissolved readily by dilute sulfuric acid (0.1N H2SO4) and the reduction product always contained sulfur to some extent. On the other hand, solubility of artificial magnetite made from Fe2O3by the reduction at the temperature range with SO2-free gas mixtures composed of CO (10%) and CO2 (20, 40 and 90%) is nearly equal to that of natural magnetite.Then we have supposed three causes for the easy dissolution of the sulfur-containing magnetite:1. The selective dissolution of the magnetite may occur electrochemically when magnetite contacts with FeS which is partially produced in magnetite under the reducing ambient with SO2by the reaction: Fe3O4+10CO+3SO2=3FeS+10CO2The first of the assumptions was not considered by the results of electrochemical potential measurements of Fe3O4and FeS in 0.1N H2SO4and 0.07M FeSO4-0.1N H2SO4solutions. The electrochemical potentials of Fe3O4in the both solutions are always more noble than those of FeS.2. The dissolution may occur by the formation of the solid solution between Fe3O4and FeS.The existunce of the solid solution was not verified from a partially sulfidized natural magnetite by the device of an electron-probe microanalyzer for KαX-ray and O KαX-ray.3. The dissolution of magnetite may be proved by hydrogen sulfide.It was confirmed experimentally that the dissolution of magnetite was proved by the evolution of H2S resulted in the reaction between FeS and H2SO4, and in general, the reducing agents showed the positive effect on the dissolution of magnetite.

Magnetite in the Hurley Copper Smelter

Three aspects of magnetite smelting are discussed. The first is the working out of equilibrium conditions for eliminating sulfur. The second is the influence of magnetite solubility on the difficulty of tapping the reverb matte. The third is an approximation of the equilibrium conditions in the reverb gases which govern whether magnetite is made or reduced in the reverb slag by these gases and by any iron sulfide in the slag.