engleski

INFLUENCE OF VARIOUS ADDINGS ON THE PRECIPITATION OF IRON OXIDES BY HYDROLYSIS OF Fe3+ IONS

Iron oxides can be applied as pigments, fillers, catalysts, sensors, magnetic recording media, carriers for drugs etc. Phase composition, size and shape of iron oxide particles play important role in these applications. The slow or forced hydrolysis of Fe3+ ions is a simple method to precipitate iron oxides, and due its simplicity is very important from the academic standpoint in the studies of nature of precipitation processes, generally. In present investigation the influence of various addings on the precipitation of iron oxides by hydrolysis of Fe(ClO4)3 and FeCl3 aqueous solutions have been investigated. The following addings were used: sodium polyanethol sulphonate (SPAS), gum arabic (GA), amidosulphonic acid (ASA) and sodium bis(2-ethylhexyl)sulfosuccionate (AOT). The iron oxide precipitates were analysed using XRD, Mössbauer, FT-IR and UV/vis/near IR spectroscopies and FE-SEM. In the presence of SPAS adding the hollow alpha-Fe2O3 particles are obtained. The walls of these particles consisted of much smaller and elongated alpha-Fe2O3 nanorods. A variety of microstructures of alpha-Fe2O3 particles were obtained in the presence of ASA and AOT addings. The substructure of these particles also consisted of elongated alpha-Fe2O3 particles. The effect of elongtion of alpha-Fe2O3 particles was explained by preferential adsorption of sulphonate/sulphate anions which favoured crystal growth in one direction. In the presence of high molecular (Mw = 250000) gum arabic nanosize alpha-Fe2O3 particles precipitated. In the case of gum arabic the strong steric effect, besides the adsorption, is involved. It was shown that Mössbauer, FT-IR and UV/vis/ near IR are sensitive to the microstructural changes of alpha-Fe2O3 particles.

nanoparticles; alpha-Fe2O3; hydrolysis; Mossbauer; XRD; FT-IR

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