Synthesis, structure and phase transformation of layered iron phenyl phosphate

Iron phenyl phosphate (FePP) was synthesized from a mixture of FeCl3 and phenyl phosphate (C6H5PO4H2) in aqueous media. X-ray diffraction (XRD) pattern of the FePP exhibited a peak at 2θ = 5.6° and a broad hump at 2θ = 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)(C6H5PO4H)1.6(H2PO4)0.4·5.1H2O. 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 FePO4·2H2O. Further, the monoclinic FePO4·2H2O transformed in orthorhombic FePO4·2H2O by aging for 120 h. The orthorhombic FePO4·2H2O 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 m2 g−1. From these results, it can be presumed that the FePP is dissolved, hydrolyzed and reprecipitated to crystalline FePO4·2H2O.