THE TRANSFORMATION OF CHLORIDE-CONTAINING GREEN RUST ONE INTO SULFATED GREEN RUST 2 BY OXIDATION IN MIXED CL- AND SO42- AQUEOUS-MEDIA

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 = [Fe2+]/[OH-] and A = [SO42-]/[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 1 --> green rust 2 --> alpha and gamma ferric oxyhydroxides. The Pourbaix diagram of iron in chloro-sulphated aqueous media is drawn in the case where A = 1/4.