FACILE SYNTHESIS OF TITANIUM PHOSPHATES 153 amount of iron ( 5% w/w) in TOP and TP is evident by the weak peaks appearing at 6.4 and 7.5 keV regions in EDX spectra. The removal of coprecipitated iron, a common impu- rity, is diffi cult and is a costly process in the production of TiO2 (26). However, the results in the present study clearly indicate that leaching of iron from ilmenite in concentrated H3PO4 is less problematic as a result of the formation of multiligand complexes such as Fe(H2PO4)2+, FeH5(PO4)22+, and FeH7(PO4)3+, which are highly soluble (27). Figure 2. X RD patterns of (A) ilmenite, (B) TOP, and (C) TP.

JOURNAL OF COSMETIC SCIENCE 154 XPS scans (see supplementary mater ial) of ilmenite and TPs show the characteristic Ti2p peak appearing at 459.3 eV. However, peak fi tting confi rms the presence of two peaks for natural ilmenite, indicating two different oxidation states for the titanium atoms. The asymmetrically broad Ti2p3/2 photoelectron peak suggests the presence of both +3 and +4 oxidation states for titanium. The two peaks observed for the Ti2p3/2 appear at 458.1 and 459.3 eV. The Ti2p and Fe2p XPS data suggest that natural weathered ilmenite used in this work contain Ti and Fe atoms in their two common oxidations states, Fe2+/Ti4+ and Fe3+/Ti3+. The appearance of an intense P2p peak at 134.3 eV and the absence of Fe2p peak in the iron region for the XPS scan of TOP clearly suggest that ilmenite has converted into TOP during acid digestion with low iron content. FTIR spectra of TPs show the chara cteristic overlapped bands in the 960–1200 cm-1 range because of antisymmetric P–O stretching vibration. The relevant bending vibra- tions appear at lower frequencies less than 670 cm-1. Based on the previously published data, it can be suggested that the phosphate ions form the ideal tetrahedral structures for the TPs (see supplementary material) (28,29). The white powder obtained with a low ir on content from digestion of ilmenite in H3PO4 is Ti(HPO4)2·H2O and calcination has led to the production of TiP2O7. Re- sults clearly confi rm the chemical identity and the morphology of synthesized Ti(HPO4)2·H2O and TiP2O7. Furthermore, XRF analysis (see supplementary mate- rial) of TOP and TP indicate the high purity of synthesized materials with trace amounts of other metals. Figure 3. T E M images and EDX analysis: (A), (B) for TOP and (C), (D) for TP.