Hierarchically porous TiO2 monolith prepared using a cellulose monolith as a template

Abstract

The photocatalytic process using TiO₂ materials under UV light illumination has shown great advantages in wastewater treatment. However, it is necessary to recover the catalyst from the suspension, and the small particle size of the catalyst can cause secondary pollution. Hierarchically porous TiO₂ monolithic materials are potential candidates for water remediation, as they can be easily recovered and can be used in flow systems. In this study, we used an ecofriendly cellulose material as a template to prepare a hierarchically porous TiO₂ monolith. The cellulose monolith template was prepared from cellulose acetate by a thermally induced phase separation method. A composite monolith was then prepared in the presence of the cellulose monolith by a typical sol–gel reaction of titanium isopropoxide (TTIP). This composite monolith was then converted to a TiO₂ monolith by burning it in air to remove the cellulose monolith. Owing to the hierarchically porous structure of the cellulose monolith template, the obtained TiO₂ monolith showed a similar hierarchically porous structure, as confirmed by scanning electron microscopy and nitrogen adsorption–desorption analyses. The pore structures could be controlled by changing the fabrication parameters, such as the type of cellulose monolith and TTIP content. The photocatalytic performance of the TiO₂ monolith was evaluated by studying its effect on the degradation of methylene blue (MB) in a flow system.