engleski

Properties of gamma-FeOOH, alpha-FeOOH and alpha-Fe2O3 particles precipitated by hydrolysis of Fe3+ ions in perchlorate containing aqueous solutions

The properties of gamma-FeOOH, alpha-FeOOH and alpha-Fe2O3 particles formed by hydrolysis of Fe3+ ions in perchlorate containing aqueous solutions were investigated using FT-IR and Mössbauer spectroscopies, TEM and FE SEM. At room temperature, slow hydrolysis of 5x10-3 M Fe(ClO4)3 solution yielded gamma-FeOOH as a single phase, whereas 1x10-2 M Fe(ClO4)3 solution yielded gamma-FeOOH as dominant phase and alpha-FeOOH as associated phase. Specific porous microstructures of laterally assembled lath-type gamma-FeOOH particles were observed. Hydrolysis of 0.1 M Fe(ClO4)3 + 0.1 M HClO4 solution at 90 oC for 21 days yielded monodisperse alpha-Fe2O3 particles with a layered substructure, whereas hydrolysis at 160 oC yielded layered and hollow substructures of alpha-Fe2O3 particles, and also showed intercrystal growth. In the absence of HClO4, upon hydrolysis of 0.1 M Fe(ClO4)3 solution at 90 oC nanosize alpha-Fe2O3 particles were obtained with the maximum fraction of their sizes in the range of ~ 15 to ~ 60 nm. The observed substructure of alpha-Fe2O3 particles caused a decrease in the hyperfine magnetic field (HMF). The hydrolysis of Fe(ClO4)3 solution containing 1 wt. % sodium dodecyl sulphate (SDS) at 90 oC yielded alpha-FeOOH particles as a single phase. An important role of the specific adsorption of sulphate head groups in the formation of alpha-FeOOH particles in the presence of SDS was suggested. FE SEM has shown that these particles are made up of much smaller alpha-FeOOH units.

Fe(ClO4)3; hydrolysis; alpha-FeOOH; gamma-FeOOH; alpha-Fe2O3; FT-IR;

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