Hierarchical titanium dioxide–cellulose monolith for removing phosphate ions from water

Abstract Phosphate adsorption can mitigate eutrophication and facilitate the recovery of elemental phosphorus from water sources; however, achieving high adsorption efficiency, reusability, and low secondary pollution using a single material remains challenging. This study evaluated the performance of a hierarchically porous titanium dioxide-modified cellulose monolith (TiO2-CM), which offers easy recovery and is suitable for continuous flow applications. A cellulose monolith (CM) was prepared from cellulose acetate via thermally induced phase separation and employed as a sustainable support scaffold. TiO2 was subsequently deposited onto the fabricated CM via a sol–gel reaction using titanium isopropoxide as the precursor. TiO2-CM exhibited a hierarchically porous structure that was attributed to CM integration, resulting in a characteristic rough and interconnected pore network. Consequently, this approach creates a highly interconnected porous architecture with a large specific surface area and low flow resistance, both of which are essential for efficient operation in continuous flow adsorption systems. Under such conditions, TiO2-CM exhibited a high adsorption capacity for phosphate ions, reaching 40.6 mg g−1, and maintained over 60% of its initial capacity after 10 successive adsorption–desorption cycles, demonstrating excellent removal efficiency and reusability. These findings highlight the practical potential of TiO2-CM as a robust and effective adsorbent for water treatment applications.