The transformation of chloride-containing green rust one into sulphated green rust two by oxidation in mixed Cl − and SO 42− aqueous media

Abstract

The mechanisms of oxidation of a ferrous hydroxide precipitated by mixing a solution of NaOH with a solution containing dissolved ferrous sulphate and chloride depend on the ratios R = 〈Fe 2+〉/〈OH −〉 and A = 〈SO 4 2−〉/〈Cl −〉 of the initial conditions. This study is limited to A = 1 4 and R ranging from 0.80 to 1.33 where the oxidation processes are governed by the formation and transformation of green rusts. The overall process is ferrous hydroxide → green rust I → green rust 2 → α and γ ferric oxyhydroxides. The Pourbaix diagram of iron in chloro-sulphated aqueous media is drawn in the case where A = 1 4 .