An integrated flow reactor-membrane filtration system for heterogeneous photocatalysis. Part I: Experiments and modelling of a batch-recirculated photoreactor

A two-part study was undertaken to examine the feasibility of combining a batch-recirculated photoreactor with a hollow-fibre membrane based ultrafiltration unit for heterogeneous photocatalysis applications. Methylene Blue (MB) and titanium dioxide (Degussa, P-25) were used as the test substrate and photocatalyst respectively for this study. This paper, which forms Part I of this study, describes the influence of MB concentration, recirculation flow rate, TiO(2) dose, solution volume in the reservoir and solution pH on the photocatalytic reaction rate. The dark adsorption of MB on the TiO(2) particle surface was also analysed. The combination of the reservoir and the annular reaction vessel could be modelled as a continuous flow stirred tank in series with a plug-flow reactor. This model predicts that the reaction rate should increase with a decrease of solution volume in the reservoir, both in the low and high substrate concentration regimes of the Langmuir-Hinshelwood kinetics formalism. This prediction was borne out by the experimental data for the low concentration regime. Part II of this series will describe experiments and modelling of the UF unit, and the operation of the combined system, respectively.