| dc.description.abstract | Photocatalytic technology is considered as one effective way for wastewater treatment. Among various photocatalysts, TiO2 is most effective catalyst for wastewater treatment. Nevertheless, ZnO has potential to substitute traditional TiO2 due to low cost, large visible light range, and good photocatalytic performance. Generally, synthetic methods for ZnO preparation include vapor condensation, physical crushing, deposition, precipitation, hydrothermal synthesis, sol-gel and microemulsion.
This study attempted to use natural polysaccharides, such as sodium alginate, chitosan, corn starch and cellulose as precursors for ZnO preparation with various conditions. Various ZnO prepared were characterized by XRD, SEM, BET and TGA, respectively. Further performances of ZnO prepared were evaluated for the removal of various pollutants including methylene blue, crystal violet and congo red. The XRD results indicated that ZnO prepared by 4 polysaccharides as precursors mainly present diffraction peaks of ZnO. It was also observed that diffraction peaks of ZnO enhance with increasing calcination temperature. In addition, SEM and BET results indicated that ZnO would present sintering as photocatalyst was calcined with a higher temperature, resulting in lower BET specific surface area. Further lower BET specific surface area may influence performance of photocatalyst. For photocatalytic test, the results indicated that ZnO prepared by sodium alginate and corn starch revealed good photocatalytic activity for removal of various pollutants. Especially, removal efficiency of crystal violet achieved with ZnO prepared by sodium alginate and corn starch could 100% after 3hr. On the contrary, ZnO prepared by chitosan revealed the lowest activity for removal of various pollutants. In addition, various preparation processes for ZnO synthesis significantly influence their characteristics and catalytic performances. Also, various operating conditions influence catalytic performance for removals of methylene blue, crystal violet and congo red. Overall, ZnO developed by this study revealed good activity and potential for wastewater treatment. | en_US |