Page 415 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

Chapter 13
Nanoaerosol

Nanomaterials are now widely used in many industries, for example, for improving
combustion efficiency, environmental protection, health, and renewable energy
production. Once these nanoparticles enter the air, they may result in nano air
pollution and have to be monitored and filtered for the protection of the environ-
ment and health. Engineering approaches to nano air pollution control is the core
part of this chapter. Specially, it will cover the properties of nano air pollution and
its implications on air monitoring and air filtration technologies.

13.1 Sources of Nanoaerosol

Nanoaerosols are nanoparticles suspended in a gas. These nanoparticles could be
liquid droplets but more often solid particles with at least one dimension being less
than 100 nm. Most researchers consider nanoaerosol as another name of ultrafine
aerosol or ultrafine particulate matter. There is actually a slight difference between
ultrafine aerosol or particulate matter and nanoaerosol. The former is commonly
used to describe airborne nanoparticles that are produced incidentally without
intension and are suspended in the atmosphere. The latter has a broader coverage
including both environmental and engineered nanoparticles in any carrier gas.
Nanoaerosols are produced from various sources intentionally or as a byproduct.
Environmental nanoaerosols are produced in the atmosphere by natural nucleation
and condensation or incomplete combustion of hydrocarbons. The latter are mostly
soot particles; a soot particle is a cluster of nanoparticles between 10 and 100 nm.
Engineered nanoaerosols are a result of recent rapid advances in nanotechnology,
produced when manufactured nanomaterials become suspended in the air or other
carrier gases. These particles usually have complex shapes including sphere, cube,
cylinder, flake, crystal, and so on. As introduced in Chap. 4, these different shapes
affect their aerodynamics.
Thousands of years ago, the Chinese started collecting soot particles from burnt
pine to make high quality ink for fine painting. This may be the earliest engineered
nanoaerosol. Nowadays, engineered nanomaterials find more applications to the

© Springer Science+Business Media Singapore 2014 395
Z. Tan, Air Pollution and Greenhouse Gases, Green Energy and Technology,
DOI 10.1007/978-981-287-212-8_13