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Aggregation Kinetics of Diesel Soot Nanoparticles in Wet Environments Chengyu Chen, and Weilin Huang Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b04575 • Publication Date (Web): 16 Jan 2017 Downloaded from http://pubs.acs.org on January 21, 2017
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Environmental Science & Technology
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Aggregation Kinetics of Diesel Soot Nanoparticles in Wet Environments
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CHENGYU CHEN AND WEILIN HUANG*
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Department of Environmental Sciences, Rutgers, The State University of New Jersey, 14 College
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Farm Road, New Brunswick, NJ 08901, United States
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* Corresponding author e-mail address:
[email protected]; phone number: (848) 932-
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5735; fax number: (732) 932-8644.
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Abstract
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Soot produced during incomplete combustion consists mainly of carbonaceous nanoparticles
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(NPs) with severe adverse environmental and health effects, and its environmental fate and
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transport are largely controlled by aggregation. In this study, we examined the aggregation
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behavior for diesel soot NPs under aqueous condition in an effort to elucidate the fundamental
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processes that govern soot particle-particle interactions in wet environments such as rain droplets
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or surface aquatic systems. The influence of electrolytes and aqueous pH on colloidal stability of
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these NPs was investigated by measuring their aggregation kinetics in different aqueous solution
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chemistries. The results showed that the NPs had negatively charged surfaces and exhibited both
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reaction- and diffusion-limited aggregation regimes with rates depended upon solution chemistry.
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The aggregation kinetics data were in good agreement with the classic Derjaguin-Landau-
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Verwey-Overbeek (DLVO) theory. The critical coagulation concentrations (CCC) were
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quantified and the Hamaker constant was derived for the soot (1.4 × 10-20 J) using the colloidal
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chemistry approach. The study indicated that, depending upon local aqueous chemistry, single
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soot NPs could remain stable against self-aggregation in typical freshwater environments and in
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neutral cloud droplets, but are likely to aggregate under salty (e.g., estuaries) and/or acidic (e.g.,
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acid rain droplets) aquatic conditions.
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Introduction
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Soot particles are airborne carbonaceous particulate matter produced from incomplete
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combustion of fuel and biomass. They are often of sizes
