Some factors influencing forced hydrolysis of FeCl3 solutions

Phase composition, size and shape of iron oxide particles produced by forced hydrolysis of Fe3+ ions depended on the concentrations of FeCl3 and HCl, and on the presence of 0.005 M quinine hydrogen sulphate (QHS). After 7 days of forced hydrolysis, alpha-Fe2O3 was produced from the 0.01 M FeCl3 solution, the mixture of beta-FeOOH and alpha-Fe2O3 was produced from 0.02 M FeCl3 solution, whereas beta-FeOOH was produced from the 0.1 M FeCl3 solution. Forced hydrolysis of the 0.1 M FeCl3 + 0.1 M HCl solution yielded alpha-Fe2O3. In the presence of 0.005 M QHS, the formation of beta-FeOOH and alpha-Fe2O3 was partially or completely suppressed in dependence on the conditions of forced hydrolysis of Fe3+ ions. Specific shapes of beta-FeOOH particles (cigar-type, X-, Y-, and star-shapes) were not obtained in the presence of 0.005 M QHS. The bundles of beta-FeOOH needles with irregular ends were obtained instead. Also, in the presence of 0.005 M QHS, the formation of alpha-FeOOH is favoured. The preferential adsorption of sulphate groups and a possible influence of quinine group at the very beginning of FeCl3 hydrolysis were suggested as responsible for the effects observed. (C) 2002 Elsevier Science B.V. All rights reserved.