Analysis of two dye-sensitized methods for improving the sunlight absorption of TiO2 using CPC photoreactor at pilot scale

Abstract

TiO2 was sensitized using an organic dye (methyl red) in order to extend the photon absorption of the catalyst toward the visible light region. Two methods of dye sensitization (in situ and ex situ), catalyst concentration, initial dye concentration and amount of dye adsorption were evaluated. Tests for diclofenac (DCF) degradation using the catalyst sensitized for both methods were carried out in a solar, pilot-scale, compound parabolic collector (CPC) photoreactor. A mechanistic model for the degradation rate of DCF was derived. The concentration of dissolved oxygen and a new parameter called sensitizing effect that quantifies the photon absorption were considered. It was found that dye-sensitized by in situ method is a simple and promising technique to substitute more costly and hazardous heavy metal systems that absorb in visible light. Besides, this method showed a superior photocatalytic perfomance under solar radiation compared with ex situ method and conventional photocatalysis based only in TiO2–P25.