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

Abstract 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 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.