Hydrolysis-precipitation studies of iron solutions. I. Model for hydrolysis and precipitation from Fe(III) nitrate solutions

Abstract Acidified iron(III) nitrate solutions of varying concentration were titrated with base (NaOH) over a temperature range (24 to 90°C) by means of a homogeneous injection technique. Changes in the optical density of the solution were also registered continuously during the titration process. The kinetic behavior of the system was studied. Based on the findings of these experimental studies it is possible to divide the hydrolysis process into four stages: (a) hydrolysis to mono- and dimers; (b) reversible, rapid growth to small polymers; (c) formation of slowly reacting large polymers; and (d) precipitation of a solid phase. A model is proposed to explain the results.