من مواضيع ahmeed19700 :
History of TiO2
The element Titanium was discovered in 1791 by William Gregor, in England. Gregor spent much of his time studying mineralogy, which led him to his discovery. This happened when he discovered a sample of a black sandy substance in his neighborhood. He studied this substance and after he was assured that it was a mineral, he called it menachanite. Four years later a man named Martin H. Klaproth, recognized that there was a new chemical element in this mineral, he later named it Titanium after the Titans, which were humongous monsters that ruled the world in Greek mythology. Martin H. Klaproth was not able to make the pure element of titanium however, he was only able to produce TiO2, or Titanium Dioxide.
Titanium dioxide (TiO2) is a multifaceted compound. It's the stuff that makes toothpaste white and paint opaque. TiO2 is also a potent photocatalyst that can break down almost any organic compound when exposed to sunlight, and a number of companies are seeking to capitalize on TiO2's reactivity by developing a wide range of environmentally beneficial products, including self-cleaning fabrics, auto body finishes, and ceramic tiles. Also in development is a paving stone that uses the catalytic properties of TiO2 to remove nitrogen oxide from the air, breaking it down into more environmentally benign substances that can then be washed away by rainfall. Other experiments with TiO2 involve removing the ripening hormone ethylene from areas where perishable fruits, vegetables, and cut flowers are stored; stripping organic pollutants such as trichloroethylene and methyl -tert-butyl ether from water; and degrading toxins produced by blue-green algae.
Titanium dioxide is a well-known photo catalyst for water and air treatment as well as for catalytic production of gases. The general scheme for the photo catalytic destruction of organics begins with its excitation by suprabandgap photons, and continues through redox reactions where OH radicals, formed on the photo catalyst surface, play a major role.
Titanium dioxide is non-toxic and therefore is used in cosmetic products (sunscreens, lipsticks, body powder, soap, pearl essence pigments, tooth pastes) and also in special pharmaceutics. Titanium dioxide is even used in food stuffs, for instance in the wrapping of salami. Small amounts added to cigar tobacco are the cause of the white ash cigar smokers so cherish.
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