Preparation of Monodispersed Hematite Particles by Forced Hydrolysis of Iron(III) Chloride-Glycine Mixed Solutions

Abstract

Preparation of monodispersed hematite particles was carried out by forced hydrolysis of aqueous mixed solutions of iron(II) chloride, glycine, and hydrochloric acid. The compositions of mixed solutions were ranged from 0.20 to 1.00 mol·dm^-3 of glycine and from 0.19 to O.71 mol·dm^-3 of hydrochloric acid at the fixed concentration of 2.0× 10^-3 mol·dm^-3 iron(III)chloride solution. The mixed solutions freshly prepared were aged at 100°C for four days in a thermostated air oven. Under the limited set of conditions, the monodispersed double sphere or dumbbell hematite particles were obtained without formation of iron (II) oxide hydroxide. For example, the large double sphere he'matite particles (-4, μm) were formed in the solution of 0.60 moldm-3 glycine and O.47 moldm-3 hydrochloric acid, which grew up with increasing hydrochloric acid concentration. Calculations using known formation constants showed that species of iron (III) chloro and glycinato complexes were dominant (ca.94% of the total iron(II) ions) in the solution at 25°C under the best conditions. Such a situation was considered to prevent formation of iron(III) oxide hydroxide and to keep appropriate concentrations of iron(III) hydroxo complexes for making suitable nucleation and growth of the monodispersed hematite particles.