Effect of hydrodynamics during sol–gel synthesis of TiO2 nanoparticles: From morphology to photocatalytic properties

Abstract In this study, the role of mixing hydrodynamics during the sol–gel synthesis of titania nanoparticles and the consequences on their photocatalytic properties were investigated. For the first time three different T -mixer geometries were tested. Alcoholic solutions of titanium tetra-isopropoxide and water were mixed in three different T -mixers with turbulence promoters and thus different mixing characteristics. The changes of nanoparticle sizes during the induction time of the sol–gel process were followed by dynamic light scattering and velocity and turbulence fields were simulated by Computational Fluid Dynamics (CFD) for the three T -mixer geometries. The results indicated that macro-mixing is crucial during the first step as it determines the nucleation rate and then the primary particle size. The micro-mixing has an influence on particle properties, especially on particle stability. Titanium dioxide nanoparticles synthesized by the sol–gel process were deposited on alumina supports. A homogeneous film of about 200 nm was deposited in all cases. Degradation of Acid Orange 7 (AO7) was used to evaluate the photocatalytic activity of TiO 2 coatings. No difference was observed between the photoactivity of synthesized TiO 2 . Total mineralization of the dye occurred after 24 h irradiation.