Aging of anodic titanium dioxide nanotubes in synthetic greywater: Assessment of stability and retention of photocatalytic activity

Anodic titanium dioxide (TiO2) nanotubes were found to be highly active photocatalysts which can be used as templates for further modification in order to tailor their photocatalytic activity for a specific application. These photocatalysts possess a high surface area despite being supported, making them suitable candidates for water treatment as no post process recovery is required. In this work, three different electrolyte compositions together with different process parameters were used to synthesise nanotube arrays having different morphologies. The mechanical and chemical stability together with their photocatalytic activity was studied following a twelve-week aging regimen. The nanotubular surfaces were exposed to flowing greywater under UV-VIS irradiation to simulate daylight. The mechanical and phase stability of the materials were found to be excellent with no degradation and change in crystalline structure being observed. The different morphologies provided different levels of resistance towards fouling with the nanotubes synthesised in the organic electrolyte being the most resistant surface. This resistance to fouling also resulted in the photocatalytic activity being sustained despite the forceful aging conditions. Overall, all the nanotube morphologies were stable making anodizing a suitable synthetic strategy to produce surfaces for real-life applications.