Synthesis, structure and phase transformation of layered iron phenyl phosphate

Abstract

Iron phenyl phosphate (FePP) was synthesized from a mixture of FeCl 3 and phenyl phosphate (C 6H 5PO 4H 2) in aqueous media. X-ray diffraction (XRD) pattern of the FePP exhibited a peak at 2 θ = 5.6° and a broad hump at 2 θ = 15–35°. The FePP was plate-like particles and gave rise to the lattice patterns having uniform alternating spacings of ca. 1.5 nm and ca. 1.2 nm. The chemical formula of FePP could be shown as Fe(OH)(C 6H 5PO 4H) 1.6(H 2PO 4) 0.4·5.1H 2O. These facts allow us to infer that the FePP was composed of a multilayer alternating bilayer of phenyl groups and amorphous iron phosphate phases. The synthetic FePP particle was aged at pH 6.0 and 85 °C for different periods of 0–120 h in aqueous media. Aging for 96 h disappeared the FePP and formed monoclinic FePO 4·2H 2O. Further, the monoclinic FePO 4·2H 2O transformed in orthorhombic FePO 4·2H 2O by aging for 120 h. The orthorhombic FePO 4·2H 2O was rod-shaped particles with the size of ca. 18 nm in width and ca. 45 nm in length and its specific surface area was 25 m 2 g −1. From these results, it can be presumed that the FePP is dissolved, hydrolyzed and reprecipitated to crystalline FePO 4·2H 2O.