One-pot photochemical synthesis of solution-stable TiO2-polypyrrole nanocomposite for the photodegradation of methyl orange

Photocatalysis is a promising technology used in wastewater treatment. However, the practical application of this approach has been hindered by several factors. One issue is the aggregation of the photocatalyst in solution which leads to significant decrease in catalytic efficiency. Recent innovations in photochemical research have geared towards improving the colloidal stability of well-known photocatalysts such as titanium dioxide (TiO2). In this study, a simple method of imparting colloidal stability to TiO2, through one-pot photo-polymerized polypyrrole (PPy) nanoparticle coatings were demonstrated. The resulting TiO2-PPy (TP) dispersions exhibited excellent resistance to aggregation as evident in their uniform particle size distribution (diameter = 81.40 ± 6.58 nm, polydispersity index = 0.412 ± 0.037) and stable zeta-potential values (ζ = 33.15 ± 4.35). The optimum TiO2 to polymer ratio also resulted to significant lowering in band-gap energy (from 3.54 eV to 3.15 eV) which is an indicator of improved photocatalytic properties. Photodegradation of a model pollutant, methyl orange (MO) performed at optimal lightning condition and 4TP dosage showed 35% /hour photocatalytic efficiency. Lastly, kinetic studies suggest that the catalytic performance is dependent on the pollutant concentration as shown by a second-order MO degradation with rate constant of 306.856 x 10-7 M-1 s-1 and proposed rate law of R = k [MO]2. The study had also indicated the chemical conversion of MO to CO2by measuring about 43% decrease in total organic carbon in an hour.