engleski

The influence of Cr-dopant on the properties of α -FeOOH particles precipitated in highly alkaline media

The effects of Cr-dopant on the phenomenology of the precipitation of acicular α -FeOOH particles, the formation of solid solutions, particle size and shape were investigated using X-ray powder diffraction (XRD), Mössbauer and Fourier transform infrared (FT-IR) spectroscopies and field emission scanning electron microscopy (FE-SEM). Acicular and monodisperse α -FeOOH particles were precipitated at a very high pH by heating suspension obtained by adding tetramethylammonium hydroxide solution into aqueous solution of FeCl3. Influence of Cr-dopant was investigated by addition of various amounts Cr³⁺ ions into starting FeCl₃ solution, where r = 100• [Cr]/([Cr]+[Fe]) represents the degree of Cr addition. XRD analysis of the obtained powders (with r value from 0 to 23.08) showed the presence only of the diffraction lines characteristic of α -FeOOH. Mössbauer spectroscopy showed a decrease in hyperfine magnetic field values of α -FeOOH sextets with an increase in Cr-addition which indicates Cr incorporation into α -FeOOH structure. OH bending bands in FT-IR spectra showed only the slight change in position with increase in r, but the considerable increase in lattice band wave number indicates a decrease in thickness of α -FeOOH particles. This conclusion was confirmed by FE-SEM observations

α -FeOOH ; chromium ; tetramethylammonium hydroxide ; XRD ; ⁵⁷Fe Mössbauer ; FT-IR ; FE-SEM

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