Preparation, characterization and photocatalytic degradation properties of a TiO2/calcium alginate composite film and the recovery of TiO2 nanoparticles

TiO2/calcium alginate (T/CA) composite films with a thickness of 0.10-0.40 mm were prepared by immobilizing titanium dioxide (TiO2) nanoparticles in a sodium alginate (SA) matrix. The T/CA film was characterized by SEM, TEM, FTIR, XRD and TGA. The photocatalytic degradation performance of the composite film was investigated. It was found that the mechanical properties and degradation rate of the T/CA film remained unchanged after 5 times of repeated use. In addition, a convenient, fast and environmental-friendly method of recycling TiO2 nanoparticles from the T/CA film was proposed in which the T/CA film was soaked in sodium citrate solution and the alginate gel could be fully dissolved. The recycled TiO2 was obtained after centrifugation, cleaning and drying. SEM, TEM, FT-IR and XRD characterization indicated that the recycled TiO2 was exactly the same as the original TiO2 and displayed the same catalytic ability. TiO2 was saved using T/CA film compared to T/CA beads.