are only marginally effective for nanoparticles.
The choice of controlling technology is limited
to only a few methods. Filtration and electrical
precipitation are widely taken to be the best
options available. Fibrous filtration can filter
NPs close to 99.999%, and a carbon wall membrane filter would be able to meet filtration efficiency up to 99.9999%. Newer technologies
include phoretic and nanomaterial approaches,
but their use in achieving clean air goals is
untested.
Monitoring is one of the greatest challenges
facing organizations that deal with indoor and
outdoor air quality. It is clear that ultrafine particles possess quite different physicochemical properties, such as ultrahigh reactivity, high number
concentration, and high surface area to mass ratio,
relative to other size classes [7]. However, data
concerning the composition and spatial/temporal
distributions of NPs are limited, making it difficult
to study their health effects [12]. There is great
interest in developing new methods for monitoring NPs; key parameters include sensitivity,
range, size resolution, and cost. Instruments for
measuring NPs can be grouped into impaction,
optical, diffusion, gravimetric, and electrical
mobility techniques. Sometimes the techniques
are combined. The micro-orifice uniform deposit
impactor (MOUDI, TSI Nano-MOUDI 125R),
laser aerosol spectrometer (LAS, TSI 3340A),
condensation particle counter (CPC TSI CPC
3750), and scanning mobility particle sizer
(SMPS, TSI 3938 E57 with 3082, 1 nm electrical
classifier and CPC 3750) are commercialized
examples of systems measuring ultrafine/fine
aerosol particles.
Nanoparticle aerosol science and technology is
a rapidly growing field. Many research papers
describe nanoparticle control and characterization
techniques in detail. It would therefore be useful
to review the field’s current status and future
vision. In this review, first, the source and health
effect of nanoparticles are summarized. This is
followed by a presentation of control technologies
for nanoparticles, including filtration methods,
electrostatic precipitators, thermophoretic and
diffusiophoretic methods, and grouping technology, with a focus on removal mechanisms for
nanoparticles, as well as the principals of each
technology, and the effects of operational and
structural parameters on removal efficiency.
These parameters are discussed by comparing
and reviewing significant studies. In addition,
measurement techniques for nanoparticles along
with their principal and comparative perspective
are presented.
Source and Health Effect of
Nanoparticles
Concern about exposure to NPs has increased
dramatically due to awareness of and increase in
anthropogenic sources involving transportation,
industry, and energy production. Specific examples include soot from diesel engines, abrasion
from tires and brake pads, smoke, and urban
smog. The developing field of nanotechnology,
producing new electronic, magnetic, optoelectronic, biomedical, pharmaceutical, cosmetic,
energy, environmental, and catalytic products
and processes, is another source of human exposure to engineered NPs. Some of the natural and
anthropogenic sources of NPs are summarized in
Table 1 [3]. In nature, NPs are produced by many
sources such as in situ photochemical reactions,
forest fires, volcanic eruptions, sea-salt spray,
microorganisms, biogenic magnetite, and so
on. Graphitic soot is produced by wildfires. Due
to their light scattering properties, NPs impact the
radiation balance of the Earth directly and indirectly and are central to the mechanisms of climate
change [14]. Many kinds of NPs are known within
organisms. Natural production of NPs can occur
through intracellular and extracellular mechanisms including within human brain cells. Many
organisms produce nanomaterials through intracellular and extracellular processes. For example,
biogenic magnetite is a kind of nanomaterial that
has been found in many microbial species including microorganisms (from bacteria to protozoa)
and in animals (e.g., human brain) and which has
been
associated
with
neurodegenerative
diseases [15].
Anthropogenic sources are estimated to
account for about 10% of total NPs. NP sources
Airborne Nanoparticles: Control and Detection
87
The choice of controlling technology is limited
to only a few methods. Filtration and electrical
precipitation are widely taken to be the best
options available. Fibrous filtration can filter
NPs close to 99.999%, and a carbon wall membrane filter would be able to meet filtration efficiency up to 99.9999%. Newer technologies
include phoretic and nanomaterial approaches,
but their use in achieving clean air goals is
untested.
Monitoring is one of the greatest challenges
facing organizations that deal with indoor and
outdoor air quality. It is clear that ultrafine particles possess quite different physicochemical properties, such as ultrahigh reactivity, high number
concentration, and high surface area to mass ratio,
relative to other size classes [7]. However, data
concerning the composition and spatial/temporal
distributions of NPs are limited, making it difficult
to study their health effects [12]. There is great
interest in developing new methods for monitoring NPs; key parameters include sensitivity,
range, size resolution, and cost. Instruments for
measuring NPs can be grouped into impaction,
optical, diffusion, gravimetric, and electrical
mobility techniques. Sometimes the techniques
are combined. The micro-orifice uniform deposit
impactor (MOUDI, TSI Nano-MOUDI 125R),
laser aerosol spectrometer (LAS, TSI 3340A),
condensation particle counter (CPC TSI CPC
3750), and scanning mobility particle sizer
(SMPS, TSI 3938 E57 with 3082, 1 nm electrical
classifier and CPC 3750) are commercialized
examples of systems measuring ultrafine/fine
aerosol particles.
Nanoparticle aerosol science and technology is
a rapidly growing field. Many research papers
describe nanoparticle control and characterization
techniques in detail. It would therefore be useful
to review the field’s current status and future
vision. In this review, first, the source and health
effect of nanoparticles are summarized. This is
followed by a presentation of control technologies
for nanoparticles, including filtration methods,
electrostatic precipitators, thermophoretic and
diffusiophoretic methods, and grouping technology, with a focus on removal mechanisms for
nanoparticles, as well as the principals of each
technology, and the effects of operational and
structural parameters on removal efficiency.
These parameters are discussed by comparing
and reviewing significant studies. In addition,
measurement techniques for nanoparticles along
with their principal and comparative perspective
are presented.
Source and Health Effect of
Nanoparticles
Concern about exposure to NPs has increased
dramatically due to awareness of and increase in
anthropogenic sources involving transportation,
industry, and energy production. Specific examples include soot from diesel engines, abrasion
from tires and brake pads, smoke, and urban
smog. The developing field of nanotechnology,
producing new electronic, magnetic, optoelectronic, biomedical, pharmaceutical, cosmetic,
energy, environmental, and catalytic products
and processes, is another source of human exposure to engineered NPs. Some of the natural and
anthropogenic sources of NPs are summarized in
Table 1 [3]. In nature, NPs are produced by many
sources such as in situ photochemical reactions,
forest fires, volcanic eruptions, sea-salt spray,
microorganisms, biogenic magnetite, and so
on. Graphitic soot is produced by wildfires. Due
to their light scattering properties, NPs impact the
radiation balance of the Earth directly and indirectly and are central to the mechanisms of climate
change [14]. Many kinds of NPs are known within
organisms. Natural production of NPs can occur
through intracellular and extracellular mechanisms including within human brain cells. Many
organisms produce nanomaterials through intracellular and extracellular processes. For example,
biogenic magnetite is a kind of nanomaterial that
has been found in many microbial species including microorganisms (from bacteria to protozoa)
and in animals (e.g., human brain) and which has
been
associated
with
neurodegenerative
diseases [15].
Anthropogenic sources are estimated to
account for about 10% of total NPs. NP sources
Airborne Nanoparticles: Control and Detection
87