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Issue 24, 1991
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Influence of inorganic and organic additives on the tailored synthesis of iron oxides


The influence of the inorganic anions, chloride, phosphate, sulphate and perchlorate and the organic molecules, n-butyl dihydrogen phosphate, 1-naphthyl disodium orthophosphate, methylphosphonic acid, phenylphosphonic acid, methylenediphosphonic acid and 1,2-ethylenediphosphonic acid, on the synthesis of iron oxides by the forced hydrolysis of aqueous FeIII solutions has been studied by electron microscopy, electron and X-ray diffraction and infrared and X-ray photoelectron spectroscopies. Haematite (α-Fe2O3) was formed in the presence of the inorganic additives. The presence of chloride and perchlorate resulted in rhombohedral crystals comprising {1014} or {1012} faces, respectively. Phosphate gave spindle-shaped crystals elongated along the c axis with stabilised faces of {hki0} form. Sulphate behaved in a similar manner but the effect was less pronounced. Computer simulations of relaxed crystal faces predicted the following order of surface energies; {1012} < {1010} < {0001} < {1210} < {1014} < {1011}. Infrared and X-ray photoelectron spectroscopies confirmed the presence of chloride, phosphate or sulphate, but not perchlorate, on the crystal surfaces. The phosphate and sulphate were bound in a bidentate manner. The organic additives, except for the diphosphonates, produced the oxyhydroxide. Iepidocrocite (γ-FeOOH), with no morphological modifications. Prismatic haematite was formed in the presence of methylenediphosphonic acid whereas 1,2-ethylenediphosphonic acid gave akaganeite (β-FeOOH). The results are discussed in terms of stereochemical and geometric interactions between adsorbed additives and selective crystal faces. Predictions of the complexation and hydrolysis behaviour of FeIII-additive species, using the partial charge model (J. Livage, M. Henry and C. Sanchez, Prog. Solid State Chem., 1988, 18, 259; N. J. Reeves and S. Mann, to be published) were in agreement with the experimental data.

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Article information

J. Chem. Soc., Faraday Trans., 1991,87, 3875-3880
Article type

Influence of inorganic and organic additives on the tailored synthesis of iron oxides

N. J. Reeves and S. Mann, J. Chem. Soc., Faraday Trans., 1991, 87, 3875
DOI: 10.1039/FT9918703875

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