Kinetics of formation of green rust 2 in the steady acidic sulphated medium

Abstract

The kinetics of formation of green rust 2, 4Fe(OH)2.2FeOOH.FeSO4.nH2O, called “GR2, was followed by Mossbauer spectroscopy in the controlled aeration of a mixture of 0.4 M FeSO4 and 0.4 M NaOH. Mossbauer spectra run at 78 K of the reaction products taken at different time intervals display an average of seven doublets. The initial products of reaction consists of a badly crystallized ferrous hydroxide, FE(OH)2., called “FH”, which disappears first at about 1/3 of the total time of formation of GR2, and sulphated ferrous hydroxide, 4Fe(OH)2.FeSO4.nH2O, called “SFH”. The kinetics of oxidation of SFH into GR2 can be described by a linear growth reaction and the transformation is considered to be in situ.