Optimisation of an annular photoreactor process for degradation of Congo Red using a newly synthesized titania impregnated kaolinite nano-photocatalyst

In this study, an annular photocatalytic reactor (APR) system was designed and operated to optimise the photocatalytic degradation of Congo Red (CR) using a newly synthesized titania impregnated kaolinite photocatalyst (TiO2/K). The design parameters of the APR: reactor configuration, mass transfer, mixing and hydrodynamics were discussed. The influences of the operation parameters: pH, critical TiO2/K loading, aeration rate and initial CR concentration on the photocatalytic performances were studied in a batch operation mode. Results showed that the initial pH was the most crucial operation parameter that significantly affected both the adsorption and photocatalytic reactions in the APR-TiO2/K system. The point of zero charge for TiO2/K was found to shift towards pH 9.5. The complete degradation of 40 ppm CR was attained in 4 h. Possible intermediates and by-products during the CR degradation were identified using the LC/MS technique. The TiO2/K reactivation study showed that the TiO2/K particles are highly stable and have a modest improvement in photoactivity for every recycle trial up to at least five cycles. The overall results revealed that the APR-TiO2/K system has promising application for the development of a technically feasible and cost-effective industrial water and wastewater treatment process. (C) 2009 Elsevier B.V. All rights reserved.