engleski

Precipitation by forced hydrolysis of Fe3+ ions in perchlorate containing aqueous solutions

Slow and forced hydrolyses of Fe(III)-salts in aqueous solutions were extensively investigated because of the importance of these reactions in natural aquatic or sediment systems and living systems on one side, and chemical syntheses and technology (corrosion problems) on the other side. The hydrolyses of Fe(III)-salts in aqueous solutions are often used as models with a view of better understanding of mechanism of hydrolyses of metal cations. The kinetics, phase composition of the precipitates, as well as the size and morphology of the particles depend on the experimental parameters such as temperature, pH, concentration of Fe3+ salts, nature of the anion present, or some other « foreign» substances, for example surfactants. In the present work we are focused on the proces of forced hydrolysis of Fe3+ ions in perchlorate-containing aqueous solution. Forced hydrolyses were conducted at 90 or 160 oC. The influence of the concentration of Fe(ClO4)3, HClO4, NaClO4 as well as selected surfactants, were investigated. The precipitates, as the solid products of Fe3+ ion hydrolysis , were analysed with XRD, Mössbauer, FT-IR and FE-SEM and EDS techniques. Hematite (alpha-Fe2O3) was principal product of hydrolysis of solutions at 90 oC. However, in the precipitates, a very small amounts of goethite (alpha-FeOOH) were found. FT-IR spectroscopy in particular was found to be very sensitive to small amounts of goethite present. Hematite was found, as a single phase in the precipitates obtained at 160 oC. However, the size and morphology of the hematite particles obtained at this temperature depended on the absence/presence of HClO4. The presence of SDS or AOT drastically change the phase composition and the microstructure of the precipitates. Hollow goethite particles were formed by aggregation mechanism

alpha-Fe2O3; alpha-FeOOH; XRD; FT-IR; Mossbauer

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