Dye Degradation by Heterogeneous and Homogeneous Photocatalysis Processes. A Scaled-up Approach for a CPC Solar Reactor

Abstract

The comparison of the solar heterogeneous photocatalysis (SHP) and solar photo Fenton (SPF) processes were carried out in a compound parabolic collector reactor, using methyl orange as a model pollutant, and the scaled-up parameters were estimated. As preliminary tests, both processes were carried out at laboratory scale (volume of 200 mL) and the accumulated energy (Qv) was registered to achieve high degradation and mineralization rates. The dye degradation by SHP in the solar reactor (volume of 30 L) was carried out using TiO₂ Degussa P25 until a Qv = 300 kJ m⁻² was reached. Under acidic condition, color removal of 95% and mineralization of 64% were achieved. The resulting reaction rates were k_app = 0.2311 L kJ⁻¹ and k_app = 0.0768 L kJ⁻¹, respectively. On the other hand, dye degradation by SPF was faster than SHP since 99% color removal and 76.5% mineralization were achieved at Qv = 10 kJ m⁻². Both processes were highly efficient in color removal and mineralization rates, at both scales. However, the SPF degradation was achieved at lower accumulated energy. The treatment capacity factor (Ct) required for the scaling-up of the solar reactor calculated for the SPF process is Ct = 6.41 kg_TOC m⁻² y⁻¹, and the area required for the treatment of a hypothetical textile effluent considering 1000 m³ y⁻¹ and initial TOC of 800 mg L⁻¹ is 125 m². These results suggest that SPF is an alternative of feasible implementation for the sanitation of textile effluents.