Temperature dependence and P/Ti ratio in phosphoric acid treatment of titanium dioxide and powder properties.
OBJECTIVE
Titanium dioxide has photocatalytic activity and is used as a white pigment for cosmetics. A certain degree of sebum on the skin is decomposed by the ultraviolet radiation in sunlight. In this work, titanium dioxide was shaken with phosphoric acid to synthesize a white pigment for cosmetics.


METHODS
Titanium dioxide was treated with 0.1 mol/L of phosphoric acid at various P/Ti molar ratios, and then shaken in hot water for 1 h. The chemical composition, powder properties, photocatalytic activity, colour phase, and smoothness of the obtained powder were studied.


RESULTS
The obtained materials indicated XRD peaks of titanium dioxide, however the peaks diminished subsequent to phosphoric acid treatment. The samples included small particles with sub-micrometer size. The photocatalytic activity of the obtained powders decreased, decomposing less sebum on the skin. Samples prepared at high P/Ti ratio with high shaking temperature indicated low whiteness in in L*a*b* colour space. The shaking and heating temperature and P/Ti ratio had influence on the smoothness of the obtained materials.


CONCLUSIONS
Phosphoric acid treatment of titanium dioxide is an effective method to inhibit photocatalytic activity for a white pigment.
Department of Informatics and Environmental Sciences, Kyoto Prefectural University, 1-5, Shimogamo Nakaragi-cyo, Sakyo-ku, Kyoto, 606-8522, Japan.
H
H
Onoda
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Matsukura
D003358:Cosmetics; D008855:Microscopy, Electron, Scanning; D010756:Phosphoric Acids / Q000737:chemistry*; D010758:Phosphorus / Q000032:analysis*; D011208:Powders; D013696:Temperature; D014025:Titanium / Q000032:analysis* / Q000737:chemistry; D014961:X-Ray Diffraction
D003358:Cosmetics; D010756:Phosphoric Acids; D011208:Powders; C009495:titanium dioxide; D010758:Phosphorus; D014025:Titanium; C030242:phosphoric acid
chemical synthesis; skin barrier; spectroscopy