A facile hydrothermal route for the synthesis of α-FeOOH with controlled morphology

Nanoscaled α-FeOOH (goethite) with controlled morphology was synthesized via hydrothermal reaction at 145–155 °C from ferrous ions and an oxidant in the presence of a cationic surfactant. The formation of α-FeOOH was confirmed by X-ray diffraction (XRD), Mössbauer spectroscopy, FT-IR analysis and visible diffuse reflectance spectroscopy. The morphology of the product was analyzed by transmission electron microscopy (TEM). The particles obtained by the proposed method have a medium size of about 35 nm. The proposed growth mechanism takes into account two possible simultaneous pathways consisting of direct electrostatic interaction between FeOH groups and cetyltrimethylammonium bromide (CTAB) and adsorption of bicarbonate ions on the α-FeOOH surface followed by complexation of CTAB through ammonium head groups.

► We use a hydrothermal route for obtaining goethite in the presence of a surfactant.
► We propose a mechanism for the crystal growth of goethite.
► Besides the direct interaction, bicarbonate ions participate in the crystal growth.
► Surfactant micelles formed after interaction with Fe-OH act as soft templates.
► The obtained particles are rodlike in shape with an average size of about 35 nm.