Study of the photocatalytic activity of clay supported TiO2 nanoparticles for methylene blue degradation.

Abstract

The photocatalytic degradation of a methylene blue (MB) solution was studied using a formulation of TiO2 nanoparticles (NPs) suspended in a commercial antibacterial paint, and supported on clay strips. All experiments were carried out in a batch reactor containing a UV-C light source and the MB solution under stirring. Parameters such as catalyst mass loading, MB concentration, as well as catalyst properties were considered for the experimental procedure. The effect of the mass loading on the photocatalytic activity of the TiO2 formulations immobilized on the clay supports was evaluated using 100, 200, and 500 mg of TiO2 on 40 mL of paint, sampling the MB solution under degradation at 0, 2, 5, 10, 20, 50, 100 and 200 min. The aliquots were analyzed by optical spectroscopy in the 400-1000 range to determine the absorbance, calculate the concentration with the Beer-Lambert equation, and obtain the amount of MB degradation. The maximum photocatalytic degradation of MB for the supported photocatalyst was 52%, 55%, and 60%, respectively. For comparison, suspended TiO2 nanoparticles lead to ca. 95% of MB photodegradation in ca. 60 min. The supported photocatalysts were tested in three consecutive cycles of 200 min to study the mechanical and photocatalytic stability. The activity of the photocatalysts with mass loading of 100 and 200 mg TiO2 decreased to ca. 35% after the three cycles, while the formulation with 500 mg TiO2 remained stable for three cycles. The final samples of each cycle were characterized by XRF, discarding erosion of the material from the support.