Influence of hydrolyzed and nonhydrolyzed Ti, Cr, and Al ions on the formation of β-FeOOH particles

Abstract

β-FeOOH particles were synthesized in the presence of Ti(IV), Al(III), and Cr(III) at metal/Fe atomic ratios of 0–0.1 by the following two methods: hydrolysis of aqueous FeCl 3 solutions added to the hydrolysis products of these metal ions (subsequent hydrolysis, SH) and hydrolysis of aqueous FeCl 3 solutions dissolving these metal ions (combined hydrolysis, CH). On increasing Al/Fe the particle size of the products with AlCl 3 by SH method steeply rose at a low Al/Fe and then fell. The similar increase of particle size was seen in SH method with Ti(SO 4) 2 though the addition of TiCl 4 decreased the particle size. In CH method, Ti(IV) markedly impeded the β-FeOOH formation but Al(III) and Cr(III) showed no influence. The particles prepared by CH and SH methods contained a large amount of Ti(IV) but a few Al(III) and Cr(III). The large spindle-shaped and rod-shaped particles produced by SH method with AlCl 3 and Ti(SO 4) 2 were highly microporous and poorly crystallized, indicating that the particles consist of fine primary particles and the aggregation of fine particles would be promoted by SO 2− 4. The different influences of the metal ions on the β-FeOOH formation were explained by their hydrolysis characteristics.