Impact of post-processing modes of precursor on adsorption and photocatalytic capability of mesoporous TiO2 nanocrystallite aggregates towards ciprofloxacin removal

The growing extent of antibiotics pollution by human activities has engendered an urgent need for adjustable approaches to their removal. The adsorption-photocatalysis technique is attractive and widely employed to address the above issue, since it does not involve other chemicals, but could achieve pollutant mineralization by the reactive species generated under the light irradiation. In this paper, three kinds of mesoporous nano-TiO₂ synthesized from titanium glycolate precursor with three different post-treatment methods [hydrothermal, calcination, and hydrothermal-calcination, denoted as TiO₂ (hydr), TiO₂ (calc), and TiO₂ (hydr + calc), respectively] were employed for the removal of ciprofloxacin (CIP) antibiotic. The variations in crystal phase and structure of TiO₂ nanocrystals from the precursor were studied in detail. The impact of post-treatment approaches on the titanium glycolate precursor in terms of adsorption capability and photocatalytic activity of TiO₂ nanocrystallite aggregates was evaluated on the removal of CIP solution. Compared to TiO₂ (calc), and TiO₂ (hydr + calc), TiO₂ (hydr) material exhibited superior capability towards CIP adsorption and photodegradation. Among the three kinds of post-processing methods, the hydrothermal treatment contributed larger surface areas and weaker hydrophilic properties which could improve the CIP molecule adsorption on the surface of the TiO₂ (hydr) materials. On the other hand, the obtained TiO₂ (hydr) displayed efficient electron-hole separation and fast charge transfer capabilities, resulting in higher photocatalytic activity towards CIP degradation initiated by holes and rad OH radicals than the other materials. In addition, the results of an antibacterial activity assay demonstrated that the degradation products of CIP solution were less harmful to the environment. This work could demonstrate that development of suitable post-processing modes for the precursor is a key issue in producing favorable materials with designed functionality.