Heterogeneous photocatalytic degradation of diuron on zinc oxide: Influence of surface-dependent adsorption on kinetics,degradation pathway,and toxicity of intermediates  

作　　者：Sutaporn Meephon Thanyada Rungrotmongkol Somchintana Puttamat Supareak Praserthdam Varong Pavarajarn 

机构地区：[1]Center of Excellence in Particle Technology, Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand [2]Biocatalyst and Environmental Biotechnology Research Unit, Department of Biochemistry, Faculty of Science, Chulalongkorn University,Bangkok 10330, Thailand [3]Bioinformatics and Computational Biology Program, Graduated School, Chulalongkorn University, Bangkok 10330, Thailand [4]Department of Chemistry, Faculty of Science, Thammasat University, Pathumthani 12120, Thailand [5]Center of Excellence on Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering,Chulalongkorn University, Bangkok 10330, Thailand [6]Research Program in Hazardous Substance Management in Agricultural Industry, Center of Excellence on Hazardous Substance Management(HSM), Bangkok 10330, Thailand

出　　处：《Journal of Environmental Sciences》2019年第10期97-111,共15页环境科学学报（英文版）

基　　金：funded by the Thailand Research Fund (No. DBG5580006)

摘　　要：Heterogeneous photocatalytic reaction has been generally applied for degradation of toxic contaminants.Degradations of a compound using the same kind of catalyst that was synthesized differently are commonly found in literature.However,the reported degradation intermediates are normally inconsistent.This issue is especially important for the degradation of toxic compounds because intermediates may be more toxic than their parent compounds and understanding the reason is necessary if appropriate catalysts are to be designed.This work systematically compares the photocatalytic degradation of diuron,a toxic recalcitrant herbicide,on two forms of zinc oxide(ZnO),i.e.,conventional particles with zinc-and oxygen-terminated polar surfaces as the dominating planes,and nanorods with mixed-terminated nonpolar surfaces.Experimental and theoretical results indicate that both the rate of reaction and the degradation pathway depend on the adsorption configuration of diuron onto the surface.Diuron molecules adsorb in different alignments on the two surfaces,contributing to the formation of different degradation intermediates.Both the aliphatic and aromatic sides of diuron adsorb on the polar surfaces simultaneously,leading to an attack by hydroxyl radicals from both ends.On the other hand,on the mixed-terminated surface,only the aliphatic part adsorbs and is degraded.The exposed surface is therefore the key factor controlling the degradation pathway.For diuron degradation on ZnO,a catalyst confined tomixed-terminated surfaces,i.e.,ZnO nanorods,is more desirable,as it avoids the formation of intermediates with potent phytotoxicity and cytogenotoxicity.Heterogeneous photocatalytic reaction has been generally applied for degradation of toxic contaminants.Degradations of a compound using the same kind of catalyst that was synthesized differently are commonly found in literature.However,the reported degradation intermediates are normally inconsistent.This issue is especially important for the degradation of toxic compounds because intermediates may be more toxic than their parent compounds and understanding the reason is necessary if appropriate catalysts are to be designed.This work systematically compares the photocatalytic degradation of diuron,a toxic recalcitrant herbicide,on two forms of zinc oxide(ZnO),i.e.,conventional particles with zinc-and oxygen-terminated polar surfaces as the dominating planes,and nanorods with mixed-terminated nonpolar surfaces.Experimental and theoretical results indicate that both the rate of reaction and the degradation pathway depend on the adsorption configuration of diuron onto the surface.Diuron molecules adsorb in different alignments on the two surfaces,contributing to the formation of different degradation intermediates.Both the aliphatic and aromatic sides of diuron adsorb on the polar surfaces simultaneously,leading to an attack by hydroxyl radicals from both ends.On the other hand,on the mixed-terminated surface,only the aliphatic part adsorbs and is degraded.The exposed surface is therefore the key factor controlling the degradation pathway.For diuron degradation on ZnO,a catalyst confined tomixed-terminated surfaces,i.e.,ZnO nanorods,is more desirable,as it avoids the formation of intermediates with potent phytotoxicity and cytogenotoxicity.

关 键 词：DIURON Photocatalysis ADSORPTION Degradation pathway Mechanism Toxicity 

分 类 号：X[环境科学与工程]