Iron(III) complexation in hydrothermal solutions – An experimental and theoretical study

A knowledge of the stability of iron complexes in hydrothermal solutions is important for quantitative interpretation of the chemical behaviour of iron in hydrothermal systems. It is generally accepted that iron is predominantly transported as Fe(II) species in reduced acid fluids whereas Fe(III) hydroxy complexes become also important in reduced alkaline solutions. Previous studies on iron transport have mainly focused on the complexation of Fe(II) with chloride ligands and the hydrolysis of Fe(II) and Fe(III) in hydrothermal solutions [e.g. 1-8]. Previous studies on Fe(III) complexes stabilities in hydrothermal solutions have only been carried out to 90°C [9-10]. The aim of this study was, therefore, to experimentally determine the stability of Fe(III) hydrolysis and chloro complex stabilities in hydrothermal solutions and complex structure using spectrophotometric measurements and theoretical calculations.