engleski

PRECIPITATION OF 1D alfa‐FeOOH in HIGHLY ALKALINE MEDIUM

Alfa‐FeOOH (goethite) particles are characterized with excellent acid‐base surface properties which can be utilized for decontamination of radioisotopes as well as for removal of toxic elements (arsenic, lead, cadmium and some others) from waste waters. The colour of alfa‐FeOOH particles may vary from lemon yellow to dark Brown and this property can be utilized in pigment applications. 1D alfa‐FeOOH particles can be used as precursor in the synthesis of 1D magnetic oxide (alfa‐Fe 2O3). In the present work we have investigated the influence of CTAB (cetyl trimethylammonium bromide)and gum arabic on the precipitation of 1D alfa‐FeOOH particles in highly alkaline medium and properties of these particles. Objective of this work is to obtain more dana about the factors which influence the microstructure of 1D alfa‐FeOOH particles and corresponding phase transformations. The precipitates were characterized with XRD, FE‐SEM, Fe Mössbauer, FT‐IR and UV/Vis/NIR techniques. 1D alfa‐FeOOH particles were precipitated by adding concentrated NaOH solution on into FeCl3 or Fe(ClO4)3 solution at pH~12.3‐12.8, followed by heating the precipitation systems at 90 or 160 ^(0)C. Precipitation from FeCl3 solution containing 1‐2 % CTAB also yielded a small fraction ofalfa‐Fe2O3 (hematite). This effect can be related with the adsorption of positively charged surfactant onto 1D alfa‐FeOOH crystallites. Advantage of 57Fe Mössbauer spectroscopy in determination of small alfa‐Fe2O3 fraction in these precipitates is shown. A strong influence of gum arabic on the precipitation of 1D alfa‐FeOOH from Fe(ClO4)3 solution in highly alkaline medium was noticed. The steric effect played also important role for observed phase and microstructural changes. The abilities of XRD, Fe Mössbauer and FT‐IR spectroscopies in determination of the phase composition of the precipitates will be discussed. UV/Vis spectra of prepared samples were also sensitive on the changes in the precipitates investigated.

1D alfa-FeOOH; CTAB; Gum Arabic; Highly alkaline medium; Precipitation; Phase transformation

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