Facile Synthesis of Titanium Phosphates from Ilmenite Mineral Sand: Potential White Pigments for Cosmetic Applications.

Ilmenite mineral sand was used to synthesize titanium bismonohydrogen orthophosphate monohydrate, Ti(HPO)·HO, and titanium phosphate, TiPO, two white pigments suitable in cosmetic applications. Ti(HPO)·HO was obtained after digesting ilmenite in 85% phosphoric acid at 150 °C for 5 hours. On standing, unreacted ilmenite and white Ti(HPO)·HO solid separated into two layers and Ti(HPO)·HO was calcined at 900 °C to obtain the crystalline TiPO. Chemical and morphological characteristics were investigated using X-ray diffraction, transmission electron microscopy, scanning electron microscopy coupled with energy dispersive X-ray analysis, Fourier-transform infrared, and X-ray photoelectron spectroscopic techniques. The water retention (WR) capacities were measured at a relative humidity of 57% and indicate that Ti(HPO)·HO and TiPO have increased WR ability when compared with the pigment grade (PG) TiO. The optical properties of Ti(HPO)·HO, TiPO, and PG-TiO were compared using Ultraviolet-visible diffuse reflectance spectroscopy. The relative photoactivity of Ti(HPO)·HO and TiPO was determined using a chemical method based on the photobleaching behavior of a stable radical, 1,1-diphenyl 2-picrylhydrazyl. The photoactivities of Ti(HPO)·HO and TiPO are lower than that of PG-TiO.