The effect of experimental conditions on the microstructure of hematite particles precipitated by the forced hydrolysis of FeCl_3 solutions

摘要

The effect of experimental conditions on the forced hydrolysis of FeCl _3 solutions and specifically the effect of amidosulphonic acid on the microstructure of precipitates were investigated. Precipitates were analyzed by XRD, ~(57)Fe M?ssbauer, FT-IR and UV/Vis/NIR spectroscopies, as well as FE-SEM. The phase transformation β-FeOOH → α-Fe _2O_3 was accelerated with an increase in the hydrolysis temperature, whereas an addition of amidosulphonic acid at the start of the hydrolysis of Fe~(3+) ions suppressed the phase transformation β-FeOOH → α-Fe_2O_3 or decreased crystallinity at 120 and 160 °C. The size and shape of hematite particles were strongly dependent on FeCl_3 concentration and temperature and the presence of sulfonate/sulfate groups. Preferential adsorption of sulfonate/sulfate groups influenced the hematite crystal growth direction. The aggregation effect was also noticed in the formation of hematite particles.