Immobilization TiO2 nanoparticles into alginate/PVP hydrogel beads for photocatalyst: effective antibiotic removal, superior recovery and reuse ability

Abstract

TiO₂ nanoparticle-loaded hydrogel bead material was prepared by the sol–gel method of alginate cross-linked in CaCl₂. TiO₂ hydrogel bead formulations were based on two methods: (1) sodium alginate mixed with polyvinylpyrrolidone (AP), together with nano TiO₂ powder (TiO₂–AP1), and (2) AP hydrogel bead soaked in solution of nano TiO₂ and CaCl₂ (TiO₂–AP2). The synthesized materials were characterized using X-ray diffraction, Fourier transform infrared spectrometer and field-emission scanning electron microscope. The photocatalytic performance of the synthesized materials was evaluated on the removal efficiency of oxytetracycline (OTC) and enrofloxacin (EFX) contained in an aqueous solution under ultraviolet (UV) light irradiation. TiO₂–AP1 beads, prepared using the first method, exhibited superior performance compared to TiO₂–AP2 beads. The porous structure of TiO₂–AP1 hydrogel beads effectively immobilized and dispersed TiO₂ particles, resulting in enhanced photocatalytic activity and stability. The best removal efficiency for OTC and EFX using TiO₂–AP1–0.4 within 240 min under UV light reached 89.5% and 82.9%, respectively. Although the photocatalytic activity of TiO₂–AP1 beads was slightly lower than that of TiO₂–P25, their separation and recovery ability from aqueous solutions were significantly better. TiO₂–AP1–0.4 maintained nearly unchanged photocatalytic activity after six degradation cycles (reduced by only about 3–4%).

Graphical abstract