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国外大学论文代写:大气中纳米微粒光催化和热生产大气污染物(ATMOSPHERIC NANOPARTICLES IN PH

Copyright 1998 Kansas State University
ATMOSPHERIC NANOPARTICLES IN PHOTOCATALYTIC AND THERMAL PRODUCTION OF ATMOSPHERIC POLLUTANTS
R.R. Chianelli1, M.J. Yácaman2,3, J. Arenas3, and F. Aldape3
1Chemistry Department, Physical Sciences Building, University of Texas at El Paso, Texas,
79968-0513. Phone: (915)-747-7555, Fax: (915)-747-5748; 2Instituto de Física, Universidad
Nacional Autónoma de México, Apdo. Postal20-364, Delegación Alvaro Obregón, 01000
México, D. F., México; and 3Instituto Nacional de Investigaciones Nucleares (ININ), Carr,
México-Toluca, km 36.5, Salazar, Edo de México, Phone: (525)518-4150, Fax: (525)616-1535
ABSTRACT
Atmospheric aerosols which occur above heavily polluted areas such as Mexico City, are characterized and found
to be complex materials that have the potential to accelerate important ozone-forming reactions photocatalytically
and thermocatalytically. In addition, because the particles are respirable, they may represent a considerable health
hazard. The aerosols consist of two intermixed components. The first component consists of amorphous
carbonaceous materials of variable composition with "fullerene like" materials dispersed throughout. The second
component is an inorganic material consisting of nanoparticles of oxides and sulfides "supported" on clay minerals.
This inorganic component has all of the characteristics of an airborne photocatalyst.
Nanoparticles of Fe2O3, MnO2 and FeS2 have demonstrated catalytic properties, particularly when they occur in
the nanoparticle range, as they do in the subject aerosol materials. These materials have band-gaps that occur in
the broad solar spectrum enhancing the photocatalytic adsorption of solar radiation beyond that of the wider bandgap
aluminosilicate and titanate materials, which also occur in aerosols. In addition, the materials are acidic and
probably are coated with moisture when suspended in air, further enhancing their catalytic ability to crack
hydrocarbons and create free radicals.
Keywords: atmospheric nanoparticles, photocatalyst, atmospheric pollutants
INTRODUCTION
Contaminated cities suffer from high levels of airborne particles which, during adverse
weather conditions, form visible clouds suspended above the cities as seen over Ciudad Juarez in
Figure 1. In addition to the catalytic effects suggested in this report, particles of the type
described also are believed to have adverse public health effects. The United States Environmental
Protection Agency (USEPA) has recently reported that particulate matter smaller than 10mm
(PM-10) increased the level of respiratory illness in children exposed to levels of 40-58 mg/m3 for
extended periods (EPA, 1993). USEPA has recently proposed to further restrict particles smaller
than 2.5mm (PM-2.5) (Chemical and Engineering News, 1997). Additionally, these airborne


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