Efficient Photocatalytic Degradation of Environmental Pollutants with Mass-Produced ZnS Nanocrystals

Photocatalytic degradation of water pollutants using nanometersized semiconductor colloids is an emerging area of environmental remediation. The synthesis of semiconductor nanocrystals (NCs), however, can be costly and result in low product yields. For large-scale photocatalytic application in envir...

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Bibliographic Details
Published in:	Journal of colloid and interface science Vol. 240; no. 2; pp. 525 - 532
Main Authors:	Torres-Martínez, Claudia L., Kho, Richard, Mian, Omar I., Mehra, Rajesh K.
Format:	Journal Article
Language:	English
Published:	San Diego, CA Elsevier Inc 15-08-2001 Elsevier
Subjects:	Applied sciences Exact sciences and technology General purification processes nanocrystals photocatalysis Pollution quantum dot semiconductor textile dye Wastewaters Water treatment and pollution quantum dot photocatalysis semiconductor textile dye nanocrystals Organic dye Photocatalysis Physicochemical purification Zinc Sulfides Waste water purification Experimental study Nanocrystal Organic compounds
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Summary:	Photocatalytic degradation of water pollutants using nanometersized semiconductor colloids is an emerging area of environmental remediation. The synthesis of semiconductor nanocrystals (NCs), however, can be costly and result in low product yields. For large-scale photocatalytic application in environmental remediation, cost-effective production of the semiconductor NCs would be ideal. Demonstrated in this report is the efficient photocatalytic degradation of p-nitrophenol (pNP) and Acid Orange 7 (AO7) using ZnS nanocrystals (∼3 to 5 nm diameter) produced in gram quantities with >50% product yield. The pNP half-life in ZnS nanocrystal photocatalyzed reactions was about 1.95 to 2.45 min, whereas in comparable TiO2 reactions, the pNP half-lives were in the range of 12 to 15 min. Absorption spectra of the photocatalysis reactions suggested the decolorization of pNP without any noticeable formation of phenolic intermediates, implying a mechanism that involves a pNP ring opening via a radical mediated attack. Likewise, the degradation of AO7 was suggested to occur via an oxidative pathway involving hydroxyl radicals formed at the photocatalyst/liquid interface. Optimum conditions for AO7 degradation such as pH, photocatalyst-to-AO7 ratio, and photocatalyst surface passivation were similar to those for pNP. By demonstrating efficient mineralization of these model pollutants using mass-produced ZnS nanocrystals, we hope to lay the foundations necessary for development of large-scale, field-applicable systems.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0021-9797 1095-7103
DOI:	10.1006/jcis.2001.7684