Objective In view of the waste of processing residues in wood processing industry, Zn2+ doped TiO2 composite photocatalyst with hierarchical porous structure of wood was prepared by impregnation calcination method. Chinese fir was used as template to improve the photocatalytic performance.
Method Taking methylene blue solution as the target degradation object, the effects of different concentrations of Zn2+ doping on the photocatalytic activity of wood template TiO2 were discussed. The photocatalytic degradation mechanism of wood template TiO2 was analyzed by XRD, SEM, XPS, BET, TEM and UV-Vis.
Result The Zn2+ doped wood template TiO2 presents good pore structure that hierarches from wood. It is a mixed crystal structure of anatase and rutile TiO2. The average grain size was 22.0 nm. The Zn2+ replaced the lattice position of Ti4+, which made the absorption wavelength of TiO2 presenting red shift in the visible region. Under UV irradiation, the degradation efficiency of methylene blue solution with 1.0% Zn-TiO2 reached 99.31%. Compared with the TiO2 without template, its degradation efficiency increased by 27%. Compared with the templated TiO2, the band gap decreased from 3.08 to 2.41 ev. The degradation efficiency can be retained 90% after five repeated experiments.
Conclusion Zn2+ doped TiO2 prepared with wood template shows excellent photocatalytic degradation performance and stability. The unique pore structure is conducive to light absorption and mass transfer, and the higher specific surface area provides more active sites for photocatalysis. Due to the difference of radius and valence state between Zn2+ and Ti4+, lattice defects will appear in the lattice, which can inhibit the recombination of photogenerated electrons and holes, increase the carrier transport and improve the photocatalytic performance. Thus, wood residues utilization with functional inorganic materials can present a promising prospect in industrial applicaion.