Influences of additives on phosphoric acid treatment of titanium dioxide as a novel white pigment

Abstract

Titanium dioxide is a photocatalytically active substance used as a white pigment for cosmetics. In sunlight, titanium dioxide catalyzes decomposition of a certain amount of sebum on the skin by ultraviolet radiation. Herein, a novel white pigment for use in cosmetics was developed from titanium dioxide and phosphoric acid at pH = 4 with and without glycerin, sodium lactate, lactic acid, and urea. The chemical composition, powder properties, photocatalytic activity, color phase, and smoothness of the samples were studied. Addition of glycerin led to a decline in the intensity of the X-ray diffraction (XRD) peak of TiO2 relative to that of the other samples. The particle size of the materials prepared with and without additives was 0.3 µm; however, extensive aggregation was observed in the obtained materials. The photocatalytic activity of TiO2 was inhibited by phosphoric acid treatment. The materials prepared with sodium lactate, lactic acid, and glycerin exhibited higher photocatalytic activity than that prepared without additives. The obtained materials showed a high reflectance in the range of visible light, and the L* values in L*a*b* color space were high (where L* defines lightness, a* denotes the red/green value, and b* the yellow/blue value). These results indicate that the samples prepared in this work are suitable for use as white pigments.