Photocatalytic degradation of atrazine using zinc oxide texturally modified with sticky rice starch template and doped with transition metals
1 Suranaree University of Technology, School of Chemistry, Institute of Science, Nakhon Ratchasima 30000, Thailand
2 National Nanotechnology Center, National Science and Technology Development Agency, Thailand Science Park, Pathumthani 12120, Thailand
3 Thammasat University, Department of Physics, Pathumthani 12121, Thailand
4 Thammasat University, Department of Chemical Engineering, Pathumthani 12121, Thailand
5 Thammasat University, Center of Excellence on Environmental Catalysis and Adsorption, Pathumthani 12121, Thailand
6 University of Oklahoma,School of Civil Engineering and Environmental Science, Norman, Oklahoma 73019, USA
2 National Nanotechnology Center, National Science and Technology Development Agency, Thailand Science Park, Pathumthani 12120, Thailand
3 Thammasat University, Department of Physics, Pathumthani 12121, Thailand
4 Thammasat University, Department of Chemical Engineering, Pathumthani 12121, Thailand
5 Thammasat University, Center of Excellence on Environmental Catalysis and Adsorption, Pathumthani 12121, Thailand
6 University of Oklahoma,School of Civil Engineering and Environmental Science, Norman, Oklahoma 73019, USA
Abstract
Atrazine is a herbicide used widely with a large quantity in Thailand and can contaminate in surface and groundwater. This work investigated atrazine removal from an aqueous solution by catalytic photodegradation using oxides of metal-cerium-zinc (M-Ce-ZnO, M = Ag, Fe, and Cu). ZnO is texturally modified with sticky rice starch template, doped with cerium (Ce) and either Ag, Fe, or Cu with the M:Ce:Zn molar ratio of 0.005:0.005:1. The catalysts were characterized by XRD, UV-Vis-DRS, and N2 adsorption-desorption analysis; and tested in a batch reactor under visible light. 0.005Ag-0.005Ce-ZnO exhibited a higher atrazine removal than 0.005Fe-0.005Ce-ZnO and 0.005Cu-0.005Ce-ZnO. Thus, a further investigation was carried out on 0.005Ag-0.005Ce-ZnO with various atrazine concentrations. The photocatalysis was explained by Langmuir-Hinshelwood-Hougen and Watson (LHHW) kinetics. The reaction rate constant was higher than the adsorption equilibrium constant indicating that the photocatalytic reaction was a key role in the atrazine removal. In the presence of humic acid, a representative of natural organic matter, a competition with atrazine was observed. To determine the degradation pathway, several intermediates were detected by liquid chromatography-mass spectrometry including 2-isopropylamino-1,3,5-triazine which was not previously reported. The efficiency of 0.005Ag-0.005CeZnO suggests a possibility for the application under the sunlight.
Keywords
atrazine; metal doped ZnO; photocatalysis; sticky rice starch; textural modification