The Mechanism of Metallic Iron Formation by the Disproportionate Reaction of Ferrous Iron

Abstract

The experimental research was conducted to elucidate the mechanism of metallic iron formation during the reaction, between l mo1/l aqueous solutions of FeC12 and NaOH through filter paper.The state analysis of iron in the precipitate was carried out to determine the metallic iron, iron compounds or ferrous hydroxide which were produced and consumed in the course of reaction.From the results obtained, the formation of metallic iron was found. to be expressed as follows.FeC12+2NaOH---Fe(OH)2+2NaC1 (10)3Fe(OH)2---Fe+2g-FeOOH+2H20 (2)In the case of inactive goethite, free energy for the process of Eq. (2)was estimated as dG2298=-3.9kcal/mol.From the pH-potential diagram for Fe-H20 system, the electrochemical steps to form metallic iron were expect as the following.3Fe(OH)2---3HFeO2-+3H+ (14)2H: FeO2---2a-FeOOH+2e (16)HFeO2-+3H+ +2e---Fe+2H20 (17)Then an over all process through the steps of(14), (16)and(17)resulted in the reaction of Eq. (2), which suggested a kind of disproportionate reaction of ferrous iron.