Some factors influencing forced hydrolysis of FeCl_3 solutions

摘要

Phase composition, size and shape of iron oxide particles produced by forced hydrolysis of Fe~(3+) ions depended on the concentrations of FeCl_3 and HC1, and on the presence of 0.005 M quinine hydrogen sulphate (QHS). After 7 days of forced hydrolysis, α-Fe_2O_3 was produced from the 0.01 M FeCl_3 solution, the mixture of β-FeOOH and α-Fe_2O_3 was produced from 0.02 M FeCl_3 solution, whereas β-FeOOH was produced from the 0.1 M FeCl_3 solution. Forced hydrolysis of the 0.1 M FeCl_3 + 0.1 M HCl solution yielded α-Fe_2O_3. In the presence of 0.005 M QHS, the formation of β-FeOOH and α-Fe_2O_3 was partially or completely suppressed in dependence on the conditions of forced hydrolysis of Fe~(3+) ions. Specific shapes of β-FeOOH particles (cigar-type, X-, Y-, and star-shapes) were not obtained in the presence of 0.005 M QHS. The bundles of β-FeOOH needles with irregular ends were obtained instead. Also, in the presence of 0.005 M QHS, the formation of α-FeOOH is favoured. The preferential adsorption of sulphate groups and a possible influence of quinine group at the very beginning of FeCl_3 hydrolysis were suggested as responsible for the effects observed.