المدونة

Titanium dioxide (TiO2) has three mineral forms, rutile, anatase and plate titanium ore, of which the rutile phase and anatase phase are tetragonal crystal system, stable at room temperature; plate titanium ore phase is rhombohedral crystal system, the crystal structure is very unstable, at present there is not much practical value in industry.

1.Titanium dioxide for photocatalysis

Titanium dioxide is a kind of amphoteric oxide, which can be oxidized as well as reduced under certain environmental conditions. When irradiated by light with energy greater than the forbidden bandwidth (also known as the band gap, Eg), the electrons (e-) in the low-energy valence band (VB) are excited to jump to the high-energy conduction band (CB), leaving positively charged holes (h+) in the valence band, which separates the photogenerated electrons from the holes. The photogenerated electrons in the conduction band are good reducing agents, reducing oxygen molecules (O2) to generate superoxide negative ions (-O2-), and the photogenerated holes in the valence band are strong oxidizing agents, oxidizing water molecules (H2O) to generate hydroxyl radicals (-OH), and then these negative ions and radicals can degrade organic pollutants in the environment into water and carbon dioxide. and carbon dioxide. It is widely recognized in the literature that the photocatalytic activity of anatase-phase titanium dioxide is significantly better than that of rutile-phase titanium dioxide. This is mainly due to:

1, anatase titanium dioxide forbidden band width Eg 3.2eV (corresponding to the energy of 387.5nm ultraviolet light), slightly larger than the rutile titanium dioxide (Eg = 3.0-3.1eV), anatase titanium dioxide generated by the electron - hole pairs of the redox ability is slightly stronger;

2, anatase-phase titanium dioxide lattice contains more defects and dislocations, which can produce more oxygen vacancies to capture electrons, resulting in easier separation of photogenerated electrons and holes, while rutile-phase titanium dioxide has a relatively weaker adsorption capacity for oxygen.

Because of its excellent photocatalytic redox properties, nano titanium dioxide has become a typical representative of photocatalytic products (optical semiconductor materials with photocatalytic function). Nano titanium dioxide coated on the surface of the substrate, in the ultraviolet light and visible light, can produce strong catalytic degradation function, effective degradation of toxic and harmful gases in the air, effectively kill a variety of bacteria and its release of toxins decomposition and harmless treatment, but also has the deodorization, deodorization, anti-fouling, purification of air and other functions.

2.Titanium dioxide is used in paint pigment and food additives.

Titanium dioxide, which is mainly used as white pigment, is also known as “titanium dioxide” and is regarded as “the best white pigment in the world”. Titanium dioxide has the highest refractive index among white pigments, so it has the highest covering power (opacity), achromatic power and other optical properties among white pigments, as well as bright whiteness, high luster, good dispersion, and compared with Lidl, it has a more economical dosage and a longer service life.

The share of titanium dioxide in the field of coatings reaches more than 90%, and it is also widely used in ink, additives for plastic and rubber, paper making, chemical fiber textile, cosmetics and other industries.

In addition, titanium dioxide is also used in food additives for whitening and filling. Titanium dioxide was listed as a Group 2B carcinogen (i.e. possibly carcinogenic to humans) by the International Agency for Research on Cancer (IARC) in 2010 and confirmed by EU regulations in 2020. Widely believed to be carcinogenic at the nanometer level, and with titanium dioxide currently being the only available whitener in the food industry, titanium dioxide was removed from the EU's classification of carcinogens in November 2022, following efforts by European paint manufacturers.

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