Developments in solar photocatalysis for destruction of organics in water.

摘要

We are developing a process that has the potential to destroy a wide range of organic contaminants in water using solar energy and a titanium dioxide photocatalyst, TiO(sub 2). Contaminated water flows through a reactor on which sunlight is focused to activate the catalyst forming hydroxyl radicals and super oxide ions. These reactive species readily attack and decompose organics in solution producing only water, CO(sub 2) and halo acids. Tests have been conducted at three levels: at a benchtop scale (liter), with a small outdoor trough (100 liters) and with a large outdoor parabolic trough (2000 liters). The experimental variables examined include ultraviolet light intensity, catalyst loading, the effect of adding hydrogen peroxide, and the performance of catalyst supports. The intensity of ultraviolet irradiation significantly affected decomposition rates of a chlorinated solvent, trichloroethylene (TCE) yielding faster reaction rates at higher intensities. The amount of catalyst in suspension affected the destruction rate of trichloroethylene; the rate increased as the amount of catalyst was increased from 0.01 to 0.1 wt%. Hydrogen peroxide used in conjunction with TiO(sub 2) significantly enhanced the photocatalytic decomposition rate of a model compound, salicylic acid, by as much as 8 times over the rate with TiO(sub 2) alone. Supported TiO(sub 2) on silica glass beads performed less effectively compared to suspended TiO(sub 2) for TCE decomposition with simulated sunlight as did TiO(sub 2) on alumina ceramic frits for decomposing salicylic acid in natural sunlight. TiO(sub 2) on fiberglass mesh performed about as well as the ceramic frits. 20 refs., 10 figs., 1 tab.