Heterogeneous photocatalytic degradation of diuron on zinc oxide: Influence of surface-dependent adsorption on kinetics, degradation pathway, and toxicity of intermediates
| Autor: | Thanyada Rungrotmongkol, Supareak Praserthdam, Somchintana Puttamat, Varong Pavarajarn, Sutaporn Meephon |
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| Rok vydání: | 2018 |
| Předmět: |
Environmental Engineering
Radical Kinetics chemistry.chemical_element 02 engineering and technology Zinc 010501 environmental sciences Photochemistry 01 natural sciences Catalysis Reaction rate Adsorption Toxicity Tests Environmental Chemistry 0105 earth and related environmental sciences General Environmental Science Photolysis Vigna General Medicine 021001 nanoscience & nanotechnology chemistry Diuron Photocatalysis Degradation (geology) Zinc Oxide 0210 nano-technology Water Pollutants Chemical |
| Zdroj: | Journal of environmental sciences (China). 84 |
| ISSN: | 1001-0742 |
| Popis: | 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 to mixed-terminated surfaces, i.e., ZnO nanorods, is more desirable, as it avoids the formation of intermediates with potent phytotoxicity and cytogenotoxicity. |
| Databáze: | OpenAIRE |
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