Characterization and dyes photocatalytic degradation of TiO₂-calcium alginate composite films and recycle of TiO₂

In order to deal with the problems that TiO₂ nanoparticles were difficult to be separated and the supported catalysts were difficult to be recycled, first, TiO₂ and sodium alginate were blended together to prepare the casting solution, and then outspread on a glass plate. TiO₂-calcium alginate (T-CA) composite films were prepared by cross-linking with calcium ion. Second, the T-CA composite films were characterized by SEM and XRD. The photocatalytic degradation of T-CA composite films for dyes was also investigated. Finally, T-CA composite films were taken out from degradation liquid of dyes, and soaked in sodium citrate aqueous solution. The binding force of citrate towards calcium ion was stronger, thus made the alginate hydrogel dissolved. After centrifugal separation of TiO₂ nanoparticles, cleaning and drying, the recycled TiO₂ was obtained. SEM, TEM, FTIR and XRD were used to characterize the recycled TiO₂. The results show that the degradation ratio of T-CA composite films for methyl orange reaches 82.37%. The recycled TiO₂ are almost exactly the same as the original TiO₂, which can be used again and the catalytic ability almost constant. So the method is an environmental-friendly, convenient and efficient method for recycling TiO₂ nanoparticle from supporters.