Self-rotating photocatalytic system for aqueous Cr(VI) reduction on TiO₂ nanotube/Ti mesh substrate

In this study, a self-rotating photocatalytic system is applied to reduce toxic Cr(VI) to non-toxic Cr(III) in aqueous solution under UV irradiation. To overcome the limitation of powdery photocatalysis, a novel approach towards a photocatalytic system for aqueous Cr(VI) reduction including self-rotating TiO₂ nanotubes on a Ti substrate (mesh type) was established.For the preparation of TiO₂ nanotubes on the Ti substrate, Ti mesh (10cm×10cm) was anodized at 50V to 25°C for 25min with mixed electrolytes (NH₄F-H₂O-C₂H₆O₂), and then annealed at 450°C for 2h in ambient oxygen at a flow rate of 400mLmin^-1. The fabricated TiO₂ nanotube arrays were uniformly grown on Ti mesh and surface characterizations was performed through the measurements of SEM, XRD, and zeta potential.The HRT (Hydraulic retention time) and rotating speeds were significantly affected by inlet flowrate in this reactor being decreased and increased, respectively, with increasing inlet flowrate. Hence, the efficiency of photocatalytic Cr(VI) reduction was observed to be highest up to 95% at the 90rpm. In addition, the rate of Cr(VI) reduction was increased by increasing the number of TiO₂/Ti meshes.