A comparative study of supported TiO₂ as photocatalyst in water decontamination at solar pilot plant scale

The degradation of gallic acid and imidacloprid with supported Millennium PC500 and Degussa P25 TiO₂ is reported. TiO₂ particles were immobilized using a titanium sol-solution and direct deposition on glass supports. The film characterization was done by x-ray diffraction, scanning electron microscopy, and atomic force microscopy, and degradation of organic compounds was monitored by high-performance liquid chromatography, total organic carbon analyzer, and ion chromatography. The experiments were performed under sunlight in compound parabolic collector plants with flat supports inside the glass tubes. Photocatalytic activity of the films was compared and identified. Although sol-gel coatings had better mechanical properties, mineralization was observed to be approximately five times slower than paste-deposited films. Photoactivity of the films decreased with silver deposition due to the nature of the organic compounds. The rate constants were calculated to be between 2 × 10^-1 and 6 × 10^-2 mg m²/kJ for organic compounds, and 6 × 10^-2 and 6 × 10^-3 for total organic carbon.