Solar-electric water purification using photocatalytic oxidation with TiO 2 as a stationary phase

Abstract

Devices for the photocatalytic oxidation of organic impurities in water are described. The aqueous stream passes over illuminated titanium dioxide attached to glass mesh, or coated as a thin film on the inside of a glass coil. Illumination may be internal using a 20 W blacklight fluorescent lamp, or external with a parabolic trough solar reflector. Decomposition rates were determined for salicylic acid, phenol, and 2- and 4-chlorophenol in single-pass and continuous recirculation modes. Up to 50% decomposition, the destruction versus illumination curves obey first-order kinetics to a good approximation over a wide range of concentrations. The positive deviation from the apparent rate constant, noticeable when the destruction is more extensive, systematically increases with reaction time. In the single-pass mode, and using solar illumination reflected by the parabolic trough, a one thousandfold decrease in a salicylic acid concentration of 1380 μg dm −3 was achieved. Some aspects of using these devices as domestic water purifiers are discussed.