Influence of nitrate and perchlorate anions on the kinetics of the goethite formation

The synthesis of goethite by oxidation of ferrous iron solutions in the pre sence of metallic iron has been carried out at temperatures ranging from 20 to 70 degrees C and initial pH form 1 to 4; air how rate is kept constant at 1 L/min. The influence of nitrate and perchlorate anions has been studie d for salt concentrations ranging from 0 to 1 mol/L. The rates of iron oxid ation and goethite precipitation are significantly enhanced. As expected, t he nitrate anion presents many more marked oxidative properties than perchl orate. Domains of precipitation of goethite have been determined and presen ted in diagrams based on the factors cited above. In the presence of nitrat e, magnetite precipitates in large domains corresponding to an increase in either temperature or pH. Ferrous iron concentrations are very low during m agnetite precipitation, below 2 x 10(-3) g/L. They remain constant during t he precipitation of goethite, in the range 12-18 x 10(-3) g/L. (C) 1998 Aca demic Press.