Photodecomposition of Chloromethanes Adsorbed on Silica Surfaces

A survey of photogeochemistry

The participation of sunlight in the natural chemistry of the earth is presented as a unique field of study, from historical observations to prospects for future inquiry. A compilation of known reactions shows the extent of light-driven interactions between naturally occurring components of land, air, and water, and provides the backdrop for an outline of the mechanisms of these phenomena. Catalyzed reactions, uncatalyzed reactions, direct processes, and indirect processes all operate in natural photochemical transformations, many of which are analogous to well-known biological reactions. By overlaying photochemistry and surface geochemistry, complementary approaches can be adopted to identify natural photochemical reactions and discern their significance in the environment.

Photochemical Properties of Precipitated Titania Aerosol Produced by Powdering of Crystal Rutile under Ambient Air

It is shown that the quantum yields of oxygen photoadsorption and carbon dioxide photodesorption on TiO2are significantly higher under illumination by quanta with energy from the surface absorption region of TiO2when it is not produced by the traditional way, but from the rutile crystal. The magnitudes and spectral dependencies of the quantum yield of photoadsorption and photodesorption for TiO2produced from a monocrystal are determined. A mechanism of a sharp increase of the titania photoadsorption activity in the surface absorption region is proposed.