WO2010003613A1

WO2010003613A1 - Electrostatic aerosol collector

Info

Publication number: WO2010003613A1
Application number: PCT/EP2009/004869
Authority: WO
Inventors: Werner Haunold; Holger Klein; Ulrich Bundke; Joachim Curtius
Original assignee: Werner Haunold; Holger Klein; Ulrich Bundke; Joachim Curtius
Priority date: 2008-07-07
Filing date: 2009-07-06
Publication date: 2010-01-14

Abstract

Physical, chemical and biological properties of aerosols such as the total mass, particle number density, spectrum of sizes, variety of shapes, biological and chemical composition of particulates are subject to atmospheric and also exhaust gas monitoring. A major problem for the sampling of aerosols via filtration, cascade impactors, etc. is that all approaches of inertial precipitation have a poor deposition efficiency for smaller particles. The method of electrostatic precipitation on conductive platforms is much better suited for collecting particulates in a wide diameter range. This method is improved in that aerosol particulates are directed into the electric field of high voltage electrode (a), where uncharged aerosol particulates and oppositely charged aerosol particulates are charged by the electric field of electrode (a) before they can contact the electrode, the distance between electrode (a) and collecting surface (c) is sufficiently close such that an electric flow exists from electrode (a) to collecting surface (c), and aerosol particulates having the charge of electrode (a) deposit on the grounded or oppositely charged collecting surface (c).

Description

Electrostatic aerosol collector State of the art

Physical, chemical and biological properties of aerosols such as the total mass, particle number density, spectrum of sizes, variety of shapes, biological and chemical composition of particulates are subject to atmospheric and also exhaust gas monitoring.

A major problem for the sampling of aerosols via filtration, cascade impactors, etc. is that all approaches of inertial precipitation have a poor deposition efficiency for smaller particles. The method of electrostatic precipitation on conductive platforms is much better suited for collecting particulates in a wide diameter range.

Point-to-plate electrostatic precipitators (ESPs) are rather simple devices that are used intensively for aerosol sampling in electron microscopic studies (H.-C. Yeh, Electrical Techniques. In : Willike and Baron, Eds, Aerosol Measurement, Van Nostrand Reinhold, New York, 410-426, 1993). The typical precipitator consists of a needle electrode (point) and a flat collecting surface (plate). A high negative voltage applied between the needle and the collecting surface generates a corona discharge, which in turn results in a high concentration of negatively charged ions near the needle tip. The aerosols particles nearby become charged by the ions and are driven to the plate by the electrostatic field. Cheng, Yeh and Kanapilly (Collection efficiencies of a point-to-plate electrostatic precipitator. American Industrial Hygiene Association Journal, 42, p. 605-610, 1981) designed an ESP according to the « Rochester design, » of Morrow and Mercer (A point-to-plate electrostatic precipitator for particle size sampling, American Industrial Hygiene Association Journal, 25, 8-14, 1964) with a sharp needle and a brass rod of 3 mm in diameter mounted across an insulating tube of 11 mm in diameter and a microscope grid being attached to the rod end to accept particles. To test its collection efficiency monodisperse aerosols were passed through this ESP and the number concentration of aerosols leaving the ESP was determined by a particle counter. Cheng, Yeh and Kanapilly claimed to achieve collection efficiencies of 85 to 90 % for aerosols with a particle size of 0.1 - 2.0 μm. However, they calculated gross deposition efficiencies according to the formula E_groSs=1-Ci/Co, wherein Ci and C₀ are the number concentrations when the voltage is turned on and off. In 2001 Laskin and Cowin (the paper was available online on January 15, 2002, On deposition efficiency of point-to- plate electrostatic precipitators) built an ESP similar to the « Rochester-design » and found that the net deposition onto a specific substrate was significantly lower than the gross precipitation determined by the loss of particles from the exiting air. The useful net deposition efficiency calculated as

wherein N_found is the number of particles found on the substrate and H_totai is the total number of particles passed through the ESP, is determined directly by counting deposited particles and does not rely on the gross loss of particles from the air stream. When comparing net deposition and gross deposition efficiencies Laskin and Cowin found that for small tip distances the gross and net deposition efficiencies nearly match each other. At higher tip distances the gross deposition rises to nearly 100 % and becomes independent of the tip position. However, the net deposition efficiency peaks near 50 % at 3 mm, then drops to a small number even though the gross deposition efficiency continues to go up. Therefore, the authors concluded that for ESPs in general an actual net deposition efficiency of more than 50 % cannot be reached and that the net deposition effiencey is rather sensitive to the needle^'s position and independent of the particle size. Hermann et al. (Sampling of atmospheric aerosols by electrostatic precipitation for direct analyses, (internet publication by Physikalisches Institut, Justus-Liebig-Universitat Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany) disclose an ESP-system for aerosol sampling featuring graphite platforms as sample collectors. As in all ESPs of the state of the art, an aerosol is passed through an inlet prefilter and along a tungsten wire with a diameter of 120 μm with a sharply grinded tip. A negative voltage of 1.2 - 1.5 kV supplied via a resistor of 30 MΩ causes a mean current of 10-15 μA and results in a corona discharge exiting the wire tip. By exposing the aerosol to the high ion densities with 10⁸-10⁹ ions s/cm³ even nanoparticles are charged with high probability. The negatively charged aerosol particulates are subsequently directed, impacted and deposited on the flat collecting surface (plate) that is either grounded or of opposite charge and is arranged perpendicular to the direction of the incoming charged aerosol.

However, the net efficiency of todays point-to-plate ESPs is still around 50 % and, thus, far from acceptable. Hence, all current ESPs require careful adjustment and their results must be compared to standards. One of the reasons for the inefficiency of current ESPs is the fact that a considerable portion of the aerosol (up to 60 % depending on the aerosol and the set up) is deposited on the electrode and not on the collecting plate.

It is the object of the present invention to provide an improved electrostatic aerosol collector (EAC), in particular one that collects a broad spectrum of particulates on the collecting surface of substrates for subsequent analysis. Another object is the provision of an EAC with higher deposition efficiency on the substrate and less loss due to deposition on the electrode. Furthermore, it is the object of the present invention to provide analytical devices for aerosols comprising an EAC of the present invention.

This object is solved by providing an electrostatic aerosol collector for collecting aerosol particulates on a collecting surface, comprising (a) at least one electrode for producing a corona discharge capable of generating an electric field suitable for negative or positive charging of aerosol particulates,

(b) at least one inlet for aerosol particulates,

(c) at least one collecting suface being either grounded or of opposite charge relative to electrode (a), characterized in that

(i) inlet (b) directs aerosol particulates into the electric field of electrode (a), where uncharged aerosol particulates and aerosol particulates charged opposite to electrode (a) are charged by the electric field of electrode (a) before they can contact electrode (a), (ii) the distance between electrode (a) and collecting surface (c) is sufficiently close that an electric flow exists from electrode (a) to collecting surface (c), and

(iii) aerosol particulates having the charge of electrode (a) deposit on the grounded or oppositely charged collecting surface (c). The EAC of the present invention is suitable for collecting charged and uncharged aerosol particulates, i.e. solids and/or liquids in a size range preferably between 1 nm up to 1 mm. For an embodiment of the inventive EAC an efficiency of more than 98 % for aerosols having a particle size of as low as about 2 μm was demonstrated (see examples). Hence, the EAC of the invention has a superior efficiency that is independent of the particle size of the aerosol particulates.

The at least one electrode (a) in the EAC produces a corona discharge that generates an electric field suitable for negatively or positively charging aerosol particulates. Preferably, electrode(s) (a) is negativley charged. The electric field charges aerosol particulates (1) without charge, (2) with an opposite charge and (3) also supercharges aerosol particulates with the same charge as electrode (a) resulting in a high mobility of all three kinds of original aerosol particulates toward the grounded or oppositely charged collecting surface (c) due to the high field strength.

One electrode (a) can be sufficient for producing an EAC of the present invention (e.g. the embodiment in Fig. 2). In a preferred embodiment the EAC of the present invention comprises at least two, preferably 3 to 12, more preferably 4 to 8, most preferably 5 to 6 electrodes (a) which are arranged circular around inlet (b), so that the aerosol particulates directed by inlet (b) are completely surrounded by electric fields resulting from said electrodes (a). A non-limiting example of such a preferred EAC is presented in Fig. 3). However, it is emphasized that the number of electrodes (a) is by no means limited. For example, the number of electrodes may be hundreds, for example, arranged as a brush.

Preferably, the one or more electrodes (a) consist of a noble metal, preferably one of high purity, more preferably gold or platinum. However, copper or stainless steel will suffice, too. The distance between electrode (a) and collecting surface (c) is not of particular relevance as long as there is an ionic flux from electrode (a) to collecting surface (c) that deposits the aerosol particulates charged by electrode(s) (a). In preferred embodiments of the present invention the distance between electrode(s) (a) and collecting surface (c) is in the range of 0,5 to 5 cm, preferably 1 ,5 to 3,5, more preferably 2 to 2,5 cm. Preferably, electrode(s) (a) has a voltage in the range of 500 to 12.000, preferably 1000 to 4000, more preferably 2500-3500 volts per cm distance between electrode (a) and collecting surface (c).

In a preferred embodiment electrode(s) (a) is a needle or wire rod, preferably a wire rod, more preferably a wire rod with a diameter of 0,01 to 1 mm, more preferably 0,08 to 0,20 mm, most preferably 0,1 to 0,15 mm. Of course, the mechanical, chemical and physical stability of the electrode must assured. Depending on the dimensions, the choice of operating conditions for electrode (a) the shape and diameter of the electrode may be adapted accordingly.

The collecting surface (c) for the inventive EAC typically comprises an electrically conductive material, preferably a metal such as e.g. gold, aluminum, graphite, copper, etc. or alloys thereof, or a semiconductor material, preferably a silicone material, most preferably a flat silicone wafer, preferably a flat silicone wafer with a black surface. It is preferred that the collecting surface is of high purity, chemically inert and removable for later analysis. It is noted that the EAC of the invention may comprise more than one collecting surface (c), e.g. a grid of surface, or a rotating collecting surface like a circular disk that rotates at predetermined times to provide clean and/or different deposition surfaces.

Inlet (b) of the EAC of the present invention is not particularly limited in its physical manifestation, instead it is limited by its function, which is to direct the incoming flow of aerosol particulates into the electric field of electrode(s) (a) but also past electrode(s) (a) itself, so that aersol particulates, in particular those of opposite charge and no charge at all do not impact and deposit on electrode(s) (a).

Contrary to the EAC of the present invention, the ESPs of the state of the art provide for an aerosol flow directed at least partially onto and into contact with the electrode. However, aerosol particulates in this flow, in particular those of opposite charge, are drawn to the electrode by its electrostatic field and impact and deposit on the electrode instead of impacting and depositing on the collecting surface. This results in a significant loss of collecting efficiency.

In preferred embodiments, inlet (b) and electrode (a) are arranged so that at least 50 %, preferably at least 70 %, more preferably at least 80 %, most prefereably at least 90, 95 or 98 % of the oppositely charged aerosol particulates and uncharged aerosol particulates in the aerosol flow from inlet (b) are charged by the electric field of electrode (a) and subsequently impacted on the collecting surface (c).

Preferably, inlet (b) of the inventive EAC is an injector, orifice or nozzle, more preferably a device resulting in a mostly laminar flow with as littel turbulent disturbances as possible. Optionally, inlet (b) may function in combination with one or more deflectors to direct the mostly laminar flow of aerosol particulates into the electrode(s) electric field but not towards the electrode(s).

It is particularly preferred that inlet (b) directs the incoming flow of aerosol particulates into the electric field of electrode (a) but past electrode (a) itself, preferably in the direction of collecting surface (c).

In another aspect, the present invention relates to a method for collecting aerosol particulates on a collecting surface (c), comprising

(i) directing aerosol particulates by means of at least one inlet (b) into the electric field of at least one electrode (a), where uncharged aerosol particulates and aerosol particulates charged opposite to electrode (a) are charged by the electric field of electrode (a) before they can contact electrode (a),

(ii) depositing aerosol particulates having the charge of electrode (a) on at least one grounded or oppositely charged collecting surface (c). In a preferred embodiment, in step (i) the aerosol particulates are directed by inlet (b) into electric fields resulting from at least two, preferably 3 to 12, more preferably 4 to 8, most preferably 5 to 6 electrodes (a) arranged circular around inlet (b). As mentioned before, the number of electrodes is not limited and may be much larger than 12.

In a preferred embodiment the distance between electrode (a) and collecting surface (c) is in the range of 0,5 to 5 cm, preferably 1 ,5 to 3,5, more preferably 2 to 2,5 cm.

In a preferred method electrode (a) has a voltage in the range of 500 to 12.000, preferably 1000 to 4000, more preferably 2500-3500 volts per cm distance between electrode (a) and collecting surface (c).

In another preferred method electrode (a) is a needle or wire rod, preferably a wire rod, more preferably one with a diameter of 0,01 to 1 mm, more preferably 0,08 to 0,20 mm, most preferably 0,1 to 0,15 mm.

Preferably, collecting surface (c) comprises an electrically conducting material, preferably a metal or semiconductor material, more preferably a silicone material, most preferably a flat silicone wafer, preferably a flat silicone wafer with a black surface. In another preferred method inlet (b) directs the incoming flow of aerosol particulates into the electric field of electrode (a) but past electrode (a) itself, preferably in the direction of collecting surface (c).

Most preferably, the method of the invention is one employing an electrostatic aerosol collector according to the invention. In a third aspect, the present invention also relates to an analytical device comprising an electrostatic aerosol collector according to the invention and a device for analysing physical, chemical and/or biological properties of the deposited aerosol particulates.

Preferably, the device for analysing physical, chemicai and/or biological properties of the precipitated aerosol particulates is selected from the group consisting of a device for atomic absorption spectroscopy (AAS), a device for gas chromatrography and/or mass spectrometry (GC/GC-MS), a scanning electron microscope (SEM) and an electron microscope (EM).

The unipolar charging of most of the aerosol particulates according to the invention adds the opportunity to use this invention favourably also in combination with other, non- collecting instruments for aerosol analysis such as a Differential Mobility Analyser

The aerosol collector can also be used to remove, i.e. filter, aerosol particulates from air or gases, preferably air or gas streams, in particular when it is intended to measure gas components without interference from aerosol particulates. Hence, and in a further aspect, the invention also relates to the use of a method of the invention for the removal of aerosol particulates from gas or air, preferably from a gas or air stream.

In analogy, it is directed to the use of an electrostatic aerosol collector according to the invention for the removal of aerosol particulates from gas or air, preferably from a gas or air stream.

In the above respect analytical devices comprising an electrostatic aerosol collector of the invention for the removal of aerosol particulates from gas or air, preferably from a gas or air stream, and a device for analysing physical, chemical and/or biological properties of the remaining gas or air are claimed. Preferably the device for analysing physical, chemical and/or biological properties of the remainning air is selected from the group consisting of a device for atomic absorption spectroscopy (AAS), a device for gas chromatrography and/or mass spectrometry (GC/GC-MS), a device for ion chromatography, a device for aerosol mass spectrometry, a transmission or scanning electron microscope (TEM or SEM) and an electron microscope (EM).

The above analytical devices are particularly useful for filtering off, i.e. separating normal or reactive aerosol particulates, e.g. soot, from reactive gas components, for example ozone or ammonia, the measurement of which is particularly prone to error due to interference with other reactive components. In the following preferred EACs according to the invention and ESPs of the prior art will be described with reference to figures which are not to be considered as limiting the scope of the appended claims in any way.

Figures Fig. 1 depicts schematically a typical electrostatic precipitator (ESP) (4) of the state of the art (similar to the ESP of Herman et al. mentioned above). An aerosol flow (1) is directed through inlet (2) consiting of tube (5) into the casing of ESP (4). Tube (5) holds a fixed deposition electrode (6) with high voltage (HV) suitable for and providing a corona discharge at its tip. Electrode (6) is a tungsten wire with a diameter of about 120 μm with a sharply grinded tip to which about 1 to 10 kV are supplied. By exposing the aerosol to high ion densities with 10⁸-10⁹ ions s/cm³ even nanoparticles are charged with high probability. The outlet of tube (5) is positioned over and directed against the center of the grounded collecting substrate (8) made from, e.g. graphite. The largest portion of the negatively charged aerosol particulates (1) deposits on the collecting substrate (8), whereas a significant portion deposits on the electrode (6) before ever reaching collecting substrate (8) or outlet (9).

Fig. 2 depicts schematically an embodiment of an EAC of the invention. An aerosol (1) of atmospheric or exhaust gas origin (a) enters the casing of the EAC (4) through inlet (2), (b) then enters the electric field (3) of the high voltage (HV) corona discharge electrode (6) positioned opposite of removable collecting substrate (8) on substrate carrier (8a), (c) becomes a negatively charged or supercharged aerosol particulate (7) and (d) subsequently impacts and deposits on the grounded or oppositely charged collecting substrate (8) as particle (10). The gas accompanying the aerosol particulates (1) now being depleted of deposited particles (10) moves to outlet (9) and out of the casing of EAC (4). The spatial arrangement of inlet (2), electrode (6) and collecting substrate (8) as well as the flow direction and velocity allow for negatively charging aerosol substrates (1) but also for impacting and depositing the charged aerosol particulates (7) before the gas stream reaches electrode (6). Hence, there is no contact of aerosol particulates (1) and electrode (6). The polarity of electrode (6) and collecting substrate (8) may be reversed. Fig. 3 depicts schematically a further embodiment of an EAC of the invention. An aerosol

(1) of atmospheric or exhaust gas origin (a) enters the casing of EAC (4) through an inlet

(2) being tube (5), (b) enters the electric field (3) of six (only two electrodes are shown) high voltage (HV) corona discharge electrodes (6) positioned alongside the inlet tube (5) opposite of removable collecting substrate (8) on substrate carrier (8a), (c) becomes negatively charged and (d) impacts and deposits on the grounded or oppositely charged collecting substrate (8). The gas accompanying the aerosol particulates (1) now being depleted of deposited particles (10) moves to outlet (9) and out of the casing of the EAC (4). The spatial arrangement of inlet (2), electrodes (6) and collecting substrate (8) as well as the flow direction and velocity allow for negatively charging aerosol substrates (1) but also for impacting and depositing the charged aerosol particulates (7) before the gas stream reaches electrodes (6). Hence, there is no contact of aerosol particulates (1) and any of electrodes (6). The polarity of electrodes (6) and collecting substrate (8) may be reversed.

Fig. 4 depicts schematically and detailed a specific embodiment of an EAC of the invention that was used for an experiment described below. An aerosol (1) of atmospheric or exhaust gas origin (a) enters the casing of EAC (4) through inlet (2), e.g. a Teflon tube (5a) with an inner diameter of 4 mm, (b) enters the electric field (3) of six (only two electrodes are shown) high voltage (HV) corona discharge electrodes (6) made of gold wire with a diameter of 0,1 mm and a length of 2 cm, positioned alongside inlet tube (5b) opposite of removable collecting substrate (8) being a silicone wafer with a diameter of 45 mm and 1 mm thick on substrate carrier (8a), a metal plate made of brass, (c) becomes negatively charged and (d) impacts and deposits on the grounded or oppositely charged collecting substrate (8). The gas accompanying the aerosol particulates (1) now being depleted of deposited particles moves to outlet (9) and out of the casing of the EAC (4). The spatial arrangement of inlet (2), tube (5b), electrodes (6) and collecting substrate (8) as well as the flow direction and velocity allow for negatively charging aerosol substrates (1) but also for impacting and depositing the charged aerosol particulates before the gas stream reaches electrodes (6). Hence, there is no contact of aerosol particulates (1) and any of electrodes (6). The polarity of electrodes (6) and collecting substrate (8) may be reversed.

Fig. 5 is a photograph of the EAC of Fig. 4 after a test run with water aerosol. The collected water droplets form a ring around inlet tube (5b). Example

The following is an example of an experiment for determining the collecting efficiency of an EAC designed according to Fig. 4 above. Physical parameters were:

- Inlet tube (5b) having an inner diameter of 8 mm and 10 mm on the outside.

- Six high voltage (HV) corona discharge electrodes (6) made of gold wire with a diameter of 0,1 mm and a length of 2 cm, arranged circular with a radius of 10 mm from the midpoint of inlet tube (5b), with a power supply of 10 kV and 10 mA (total for all electrodes).

- Distance of the six electrode wire tips to the collecting substrate (8): 25 to 30 mm.

- Distance between tube (5b) and collecting substrate (8) : 10 mm.

- Collecting substrate : a silicone wafer with a diameter of 45 mm and 1 mm thick on substrate carrier (8a). - Gas flow : 2 to 5 I per minute

- Aerosol composition - city air from Frankfurt or artificial mineral test dust.

Repeated experiments conducted with the EAC depicted in Fig. 4 employing the above conditions led to a net absorption efficiency of more than 98 % as determined with a Hydro CPC Type 3785 of the TSI company, US. Using a microbalance it was found that more than 95 % of the aerosol particulates introduced into the EAC were actually deposited on the collecting silicon wafer.

Claims

1. Electrostatic aerosol collector for collecting aerosol particulates on a collecting surface, comprising (a) at least on electrode for producing a corona discharge capable of generating an electric field suitable for negatively or positively charging aerosol particulates,

(b) at least one inlet for aerosol particulates,

(iii) aerosol particulates having the charge of electrode (a) deposit on the grounded or oppositely charged collecting surface (c).

2. Electrostatic aerosol collector according to claim 1 , wherein at least two, preferably 3 to 12, more preferably 4 to 8, most preferably 5 to 6 electrodes (a) are arranged circular around inlet (b), so that the aerosol particulates directed by inlet (b) are completely surrounded by electric fields resulting from said electrodes (a).

3. Electrostatic aerosol collector according to claim 1 or 2, wherein electrode (a) consists of a noble metal, preferably gold or platinum.

4. Electrostatic aerosol collector according to any one of claims 1 to 3, wherein the distance between electrode (a) and collecting surface (c) is in the range of 0,5 to 5 cm, preferably 1 ,5 to 3,5, more preferably 2 to 2,5 cm.

5. Electrostatic aerosol collector according to any one of claims 1 to 4, wherein electrode (a) has a voltage in the range of 500 to 12.000, preferably 1000 to 4000, more preferably 2500-3500 volts per cm distance between electrode (a) and collecting surface (c).

6. Electrostatic aerosol collector according to any one of claims 1 to 5, wherein electrode (a) is a needle or wire rod, preferably a wire rod, more preferably one with a diameter of 0,01 to 1 mm, more preferably 0,08 to 0,20 mm, most preferably 0,1 to 0,15 mm.

7. Electrostatic aerosol collector according to any one of claims 1 to 6, wherein collecting surface (c) comprises an electrically conductive material, preferably a metal or semiconductor material, more preferably a silicone material, most preferably a flat silicone wafer, preferably a flat silicone wafer with a black surface.

8. Electrostatic aerosol collector according to any one of claims 1 to 7, wherein inlet (b) directs the incoming flow of aerosol particulates into the electric field of electrode (a) but past electrode (a) itself, preferably in the direction of collecting surface (c).

9. Method for collecting aerosol particulates on a collecting surface (c), comprising (i) directing aerosol particulates by means of at least one inlet (b) into the electric field of at least one electrode (a), where uncharged aerosol particulates and aerosol particulates charged opposite to electrode (a) are charged by the electric field of electrode (a) before they can contact electrode (a),

(ii) depositing aerosol particulates having the charge of electrode (a) on at least one grounded or oppositely charged collecting surface (c).

10. Method according to claim 9, wherein in step (i) the aerosol particulates are directed by inlet (b) into electric fields resulting from at least two, preferably 3 to 12, more preferably 4 to 8, most preferably 5 to 6 electrodes (a) arranged circular around inlet (b).

11. Method according to claim 9 or 10, wherein the distance between electrode (a) and collecting surface (c) is in the range of 0,5 to 5 cm, preferably 1 ,5 to 3,5, more preferably 2 to 2,5 cm.

12 Method according to any one of claims 9 to 11 , wherein electrode (a) has a voltage in the range of 500 to 12.000, preferably 1000 to 4000, more preferably 2500-3500 volts per cm distance between electrode (a) and collecting surface (c).

13. Method according to any one of claims 9 to 12, wherein electrode (a) is a needle or wire rod, preferably a wire rod, more preferably one with a diameter of 0,01 to 1 mm, more preferably 0,08 to 0,20 mm, most preferably 0,1 to 0,15 mm.

14. Method according to any one of claims 9 to 13, wherein collecting surface (c) comprises an electrically conducting material, preferably a metal or semiconductor material, more preferably a silicone material, most preferably a flat silicone wafer, preferably a flat silicone wafer with a black surface.

15. Method according to any one of claims 9 to 14, wherein inlet (b) directs the incoming flow of aerosol particulates into the electric field of electrode (a) but past electrode (a) itself, preferably in the direction of collecting surface (c).

16. Method of claim 9 employing an electrostatic aerosol collector according to any one claims 1 to 8.

17. Analytical device comprising an electrostatic aerosol collector according to any one claims 1 to 8 and a device for analysing physical, chemical and/or biological properties of the deposited aerosol particulates.

18. An analytical device according to claim 17, wherein the device for analysing physical, chemical and/or biological properties of the precipitated aerosol particulates is selected from the group consisting of a device for atomic absorption spectroscopy (AAS), a device for gas chromatrography and/or mass spectrometry (GC/GC-MS), a device for ion chromatography, a device for aerosol mass spectrometry, a transmission or scanning electron microscope (TEM or SEM) and an electron microscope (EM).

19. Use of a method according to any of claims 9 to 18 for the removal of aerosol particulates from gas or air, preferably from a gas or air stream.

20. Use of an electrostatic aerosol collector according to any one of claims 1 to 7 for the removal of aerosol particulates from gas or air, preferably from a gas or air stream.

21. Analytical device comprising an electrostatic aerosol collector according to any one claims 1 to 8 for the removal of aerosol particulates from gas or air, preferably from a gas or air stream, and a device for analysing physical, chemical and/or biological properties of the remaining gas or air.

22. An analytical device according to claim 21 , wherein the device for analysing physical, chemical and/or biological properties of the remainning air is selected from the group consisting of a device for atomic absorption spectroscopy (AAS), a device for gas chromatrography and/or mass spectrometry (GC/GC-MS), a device for ion chromatography, a device for aerosol mass spectrometry, a transmission or scanning electron microscope (TEM or SEM) and an electron microscope (EM).