WO2003078036A1 - Method of filtering particules from a liquid, liquid filtering device and membrane - Google Patents

Method of filtering particules from a liquid, liquid filtering device and membrane Download PDF

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Publication number
WO2003078036A1
WO2003078036A1 PCT/NL2003/000204 NL0300204W WO03078036A1 WO 2003078036 A1 WO2003078036 A1 WO 2003078036A1 NL 0300204 W NL0300204 W NL 0300204W WO 03078036 A1 WO03078036 A1 WO 03078036A1
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WO
WIPO (PCT)
Prior art keywords
membrane
liquid
flow channel
electrode
pores
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Application number
PCT/NL2003/000204
Other languages
French (fr)
Inventor
Nicolaas Arnold Petrus Denis
Arie Hendrik Van Heeren
Douwe Erik Van De Kerk
Original Assignee
Fluxxion B.V.
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Publication date
Application filed by Fluxxion B.V. filed Critical Fluxxion B.V.
Priority to AU2003220770A priority Critical patent/AU2003220770A1/en
Publication of WO2003078036A1 publication Critical patent/WO2003078036A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/022—Metals
    • B01D71/0227—Metals comprising an intermediate layer for avoiding intermetallic diffusion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0081—After-treatment of organic or inorganic membranes
    • B01D67/0088—Physical treatment with compounds, e.g. swelling, coating or impregnation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
    • B01D61/425—Electro-ultrafiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
    • B01D65/08—Prevention of membrane fouling or of concentration polarisation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/10—Supported membranes; Membrane supports
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/022—Metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
    • B01D2321/22—Electrical effects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/26—Electrical properties

Definitions

  • the invention relates to a method for selectively filtering macroscopic particles according to size from a liquid, wherein the liquid is guided through pores in a membrane, to a liquid filtering device for carrying out the method and a membrane for use in such a device.
  • the method according to the invention filters particles which are, for instance, larger than a minimum size in the order of magnitude of one micron, from the liquid flow.
  • a membrane in which pores have been provided made to have a particular size, for instance a size in the range of 0.1 to 10 micrometers, so that, in a selective manner, the pores do not allow larger particles to pass. It is known, for instance, to make such membranes through a photolithographic process from ceramic material.
  • the invention provides a method for selectively filtering macroscopic particles according to size from a liquid, wherein - the liquid is guided through a flow channel, - the liquid is guided through pores, selecting according to size, in a membrane in the flow channel, which membrane comprises a conductive layer or is conductive;
  • a potential difference between the conductive layer and an electrode in the flow channel or in a wall of the flow channel is applied, with which an electric field in the liquid resulting from a net charge on a surface of the membrane as a result of ion exchange between the liquid and the membrane is substantially compensated.
  • the membrane as a whole can form the conductive layer mentioned, but it can also contain other layers.
  • An important factor for the through-flow of macroscopic particles through a membrane appears to be the effect called the electrokinetic potential. Often, the macroscopic particles are charged, or collect an envelope of polarized liquid around them. As a result, they are sensitive to electric fields.
  • Such fields can occur, for instance, through selective dissolution of ions from the membrane or selective precipitation of ions on the membrane as a result of surface effects, leading to a charge separation in the liquid.
  • Such an electric field repels the macroscopic, charged particles from the membrane so that they can no' longer reach the pores, or, conversely, attracts them, so that they are retained at the membrane or in the pores.
  • a high pressure gradient is required to have the particles flow through.
  • This effect is controlled by applying a potential difference between the membrane and the electrodes in the liquid.
  • the potential difference compensates the electric field caused by the charge on the membrane and/or reduces the dissolution or the precipitation on the membrane. Therefore, the electric field serves for unhindered through-flow and preferably not for generating electrolytic effects on the membrane or even merely accelerating the macroscopic particles. This latter would, conversely, lead to reduced through-flow of the particles elsewhere in the liquid channel.
  • electrodes with a potential are present on both sides of the membrane, so that the potential difference with the membrane has the same direction on both sides of the membrane.
  • the potential difference on both sides of the membrane is rendered so high that the field resulting from the charge on the membrane is compensated. Consequently, the through-flow of the particles passing through the membrane is influenced as little as possible by electric fields in the liquid.
  • the membrane is manufactured by providing photolithographic pores of the desired sizes in a carrier of, for instance, ceramic material, and to provide the carrier with a conductive layer.
  • the conductive layer is applied after the provision of the pores so that also in the pores, no electric fields occur hindering the transport of macroscopic particles.
  • the carrier itself is of conductive material.
  • Fig. 1 shows a filtering device
  • Fig. 2 shows a charge distribution around a membrane
  • Fig. 3 shows a part of a membrane.
  • Fig. 1 shows a filtering device with a liquid supply 10, a liquid discharge 12 and, therebetween, a channel 14 with a membrane 16 and a first and second electrode 17a,b therein.
  • the electrodes 17a,b are included in the channel 14 on opposite sides of the membrane 16.
  • the filtering device contains a voltage source 18, a first pole of which is coupled to the membrane 16 and a second pole to both electrodes 17a,b (in one embodiment, the voltage source 18 is a short circuit).
  • the wall or a part of the wall of the channel 14 can function as electrodes. In this case, no separate electrodes 17a,b need to be included in the channel 14.
  • the Avail of the channel 14 and/or a connection between the membrane 16 and the wall of the channel and/or a connection between the wall and the electrodes 17a, b is, at least locally between the membrane 16 and the electrodes 17a,b, not or hardly conductive, so that a voltage of the voltage source 18 generates no great currents through the wall of the channel 14 of the membrane 16 to the electrodes 17a,b which make the voltage sag.
  • the connection between the wall and the membrane 16, and/or a further part of the wall connecting the membrane to the parts of the wall functioning as electrode is not or hardly conductive.
  • the membrane 16 serves for stopping macroscopic particles having a magnitude over a threshold value of, for instance, some microns.
  • the membrane 16 contains pores connecting the two flat sides of the membrane 16, with a pore size corresponding to the threshold value.
  • the membrane contains a large number of pores of the same size, for instance a size in the range of one-tenth to ten micrometers.
  • the electrodes 17a,b serve for applying an electric field, but otherwise, if they are present in the liquid flow at all, allow passage of particles with a size over the threshold value.
  • a part of the wall of the liquid channel serves as an electrode, this is self-evident.
  • the electrodes 17a,b contain, for instance, a metal gauze with holes of a magnitude over one-tenth of a millimeter or a lattice-work with such openings.
  • the device forces liquid to flow through the channel 14 from the supply 10 to the discharge 12, for instance by pumping the liquid away with the discharge 12 and/or by applying pressure to the liquid in the supply. Consequently, a pressure gradient is formed which makes the liquid flow.
  • the liquid is thereby forced to flow through pores in the membrane 16.
  • Macroscopic particles are then carried along with the liquid flow.
  • a part of the macroscopic particles is then carried along through the pores in the membrane 16, but macroscopic particles of a magnitude too large for the pores are stopped by the membrane 16 and do no longer flow along with the liquid.
  • the .contact between the liquid and the membrane 16 makes it possible for ions of the membrane to selectively dissolve and/or selectively precipitate on the membrane 16. For instance, on the surface, OH-groups can yield H+ions to the liquid. Due to this type of charge separation, a net charge is formed on the surface of the membrane 16. The net charge generates an electric field, whose field fines run through the liquid.
  • Fig. 2 shows the field strength of this field as a function of the distance to the membrane 16 in the absence of flow (not to scale).
  • the field strength is proportional to the spatial integral of the charge.
  • a jump in the field strength occurs because of the charge on the surface of the membrane 16.
  • the field strength decreases again because the liquid has a location-dependent net charge. This net charge is formed in that particles with different charges are attracted to and repelled from the membrane, respectively, by the electric field.
  • the transport of macroscopic particles to and selectively through the membrane 16 occurs in that these particles are carried along by the flow of the liquid.
  • the electric field counteracts the flow of the liquid carrying along charged macroscopic particles through the membrane. Particles having the same charge as the membrane 16 are repelled upstream of the membrane, particles having an opposite charge to the membrane 16 are retained downstream of the membrane.
  • the field that is generated by the net charge on the surface of the membrane 16 is compensated by utilizing a conductive membrane 16 or a membrane 16 with at least one conductive layer and by using the voltage source 18 between the membrane 16 and the electrodes 17a,b and/or the wall of the channel 14.
  • the voltage source virtually as much, but opposite, charge is introduced into the membrane or in the conductive layer as there is charge present on the surface of the membrane.
  • the field generated by the charge on the membrane is compensated.
  • the membrane does not generate an electric field in the liquid.
  • the field is already removed by bringing the conductive layer to the same potential as the electrodes 17a,b in the liquid. But depending on the liquid, an improved through-flow effect can be obtained by applying a potential difference between the membrane 16 and the electrodes 17a,b.
  • the effect of the electric field on the through-flow upstream of the membrane is the strongest. That is why, preferably, in any case upstream of the membrane the field is removed.
  • the field on both sides of the membrane 16 is removed, leading to optimal through-flow.
  • the electrodes 17a,b are then brought to the same potential at both sides of the membrane 16, so that they have the same potential difference relative to the membrane 16 (or both the same potential as the membrane 16).
  • Fig. 3 shows, in side view, a detail of a cross section of a membrane 16 for use as liquid filter in a device as shown in Fig. 1.
  • the side view contains one single pore 32, but it will be clear that the membrane contains many such pores: one pore has, for instance, a size of 0.5 micrometer, and the distance between different pores can be in the order of magnitude of 10 micrometers, with the membrane having a magnitude of several centimeters.
  • the membrane 16 is made of a ceramic carrier 30, in which photolithographic pores 32 of a particular size have been etched. Thereupon, a conductive layer 34 is applied onto the surface of the carrier 30, so that the conductive layer 34 also continues into the pores.
  • the conductive layer 34 in the pores can be omitted, for instance by first applying the conductive layer 34 onto the Garrier 30 and then etching the pores, or conversely, by selecting a deposition technique which only covers the surface of the membrane and not the inside of the pore.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Health & Medical Sciences (AREA)
  • Urology & Nephrology (AREA)
  • Manufacturing & Machinery (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

Macrosopic particules are selectively filtered according to size from a liquid by the pore (32) in a membrane (16). The membrane (16) comprises a conductive layer (34) or is conductive as a whole. With a voltage source (18), a potential difference is applied between the conductive layer (34) and an electrode (17a, 17b) in the flow channel (14) or in a wall of the flow channel (14). Thus, an electric field in the liquid, resulting from a net charge on a surface of the membrane (16) as a result of ion exchange between the liquid and the membrane (16) is substantially compensated.

Description

METHOD OF FILTERING PARTICLES FROM A LIQUID, LIQUID FILTERING DEVICE AND
MEMBRANE
The invention relates to a method for selectively filtering macroscopic particles according to size from a liquid, wherein the liquid is guided through pores in a membrane, to a liquid filtering device for carrying out the method and a membrane for use in such a device. The method according to the invention filters particles which are, for instance, larger than a minimum size in the order of magnitude of one micron, from the liquid flow. To this end, use is made of a membrane in which pores have been provided, made to have a particular size, for instance a size in the range of 0.1 to 10 micrometers, so that, in a selective manner, the pores do not allow larger particles to pass. It is known, for instance, to make such membranes through a photolithographic process from ceramic material.
However, it has appeared that in certain cases, the flow velocity of the particles through the membrane is lower than might be expected on hydrodynamic grounds. Sometimes, this even occurs to a degree such that although the liquid flows through the membrane in a normal manner, hardly any macroscopic particles flow along, not even particles of a smaller size than the pores. Primarily, this could of course be caused by larger particles clogging the pores, but the problem remains even when evident measures are taken to remove larger particles. Only by applying a high pressure gradient across the membrane, will the particles flow through the membrane.
It is inter alia an object of the invention to improve the through-flow of particles through pores in a membrane in such a liquid filter device and method, without a high pressure gradient being required.
The invention provides a method for selectively filtering macroscopic particles according to size from a liquid, wherein - the liquid is guided through a flow channel, - the liquid is guided through pores, selecting according to size, in a membrane in the flow channel, which membrane comprises a conductive layer or is conductive;
- with a voltage source, a potential difference between the conductive layer and an electrode in the flow channel or in a wall of the flow channel is applied, with which an electric field in the liquid resulting from a net charge on a surface of the membrane as a result of ion exchange between the liquid and the membrane is substantially compensated. The membrane as a whole can form the conductive layer mentioned, but it can also contain other layers. An important factor for the through-flow of macroscopic particles through a membrane appears to be the effect called the electrokinetic potential. Often, the macroscopic particles are charged, or collect an envelope of polarized liquid around them. As a result, they are sensitive to electric fields. Such fields can occur, for instance, through selective dissolution of ions from the membrane or selective precipitation of ions on the membrane as a result of surface effects, leading to a charge separation in the liquid. Such an electric field repels the macroscopic, charged particles from the membrane so that they can no' longer reach the pores, or, conversely, attracts them, so that they are retained at the membrane or in the pores. As a consequence, a high pressure gradient is required to have the particles flow through.
This effect is controlled by applying a potential difference between the membrane and the electrodes in the liquid. The potential difference compensates the electric field caused by the charge on the membrane and/or reduces the dissolution or the precipitation on the membrane. Therefore, the electric field serves for unhindered through-flow and preferably not for generating electrolytic effects on the membrane or even merely accelerating the macroscopic particles. This latter would, conversely, lead to reduced through-flow of the particles elsewhere in the liquid channel. In one embodiment, electrodes with a potential are present on both sides of the membrane, so that the potential difference with the membrane has the same direction on both sides of the membrane. Preferably, the potential difference on both sides of the membrane is rendered so high that the field resulting from the charge on the membrane is compensated. Consequently, the through-flow of the particles passing through the membrane is influenced as little as possible by electric fields in the liquid.
Preferably, the membrane is manufactured by providing photolithographic pores of the desired sizes in a carrier of, for instance, ceramic material, and to provide the carrier with a conductive layer. Preferably, the conductive layer is applied after the provision of the pores so that also in the pores, no electric fields occur hindering the transport of macroscopic particles. In an alternative, the carrier itself is of conductive material.
These and other objectives and advantageous aspects of the device and method according to the invention will be further described with reference to the following figures.
Fig. 1 shows a filtering device;
Fig. 2 shows a charge distribution around a membrane; Fig. 3 shows a part of a membrane.
Fig. 1 shows a filtering device with a liquid supply 10, a liquid discharge 12 and, therebetween, a channel 14 with a membrane 16 and a first and second electrode 17a,b therein. The electrodes 17a,b are included in the channel 14 on opposite sides of the membrane 16. The filtering device contains a voltage source 18, a first pole of which is coupled to the membrane 16 and a second pole to both electrodes 17a,b (in one embodiment, the voltage source 18 is a short circuit). Optionally, also the wall or a part of the wall of the channel 14 can function as electrodes. In this case, no separate electrodes 17a,b need to be included in the channel 14.
The Avail of the channel 14 and/or a connection between the membrane 16 and the wall of the channel and/or a connection between the wall and the electrodes 17a, b is, at least locally between the membrane 16 and the electrodes 17a,b, not or hardly conductive, so that a voltage of the voltage source 18 generates no great currents through the wall of the channel 14 of the membrane 16 to the electrodes 17a,b which make the voltage sag. In case the wall or a part thereof functions as an electrode, the connection between the wall and the membrane 16, and/or a further part of the wall connecting the membrane to the parts of the wall functioning as electrode, is not or hardly conductive.
The membrane 16 serves for stopping macroscopic particles having a magnitude over a threshold value of, for instance, some microns. To that end, the membrane 16 contains pores connecting the two flat sides of the membrane 16, with a pore size corresponding to the threshold value. For instance, the membrane contains a large number of pores of the same size, for instance a size in the range of one-tenth to ten micrometers.
The electrodes 17a,b serve for applying an electric field, but otherwise, if they are present in the liquid flow at all, allow passage of particles with a size over the threshold value. When a part of the wall of the liquid channel serves as an electrode, this is self-evident. When separate electrodes 17a,b are used, the electrodes 17a,b contain, for instance, a metal gauze with holes of a magnitude over one-tenth of a millimeter or a lattice-work with such openings. In operation, the device forces liquid to flow through the channel 14 from the supply 10 to the discharge 12, for instance by pumping the liquid away with the discharge 12 and/or by applying pressure to the liquid in the supply. Consequently, a pressure gradient is formed which makes the liquid flow. The liquid is thereby forced to flow through pores in the membrane 16. Macroscopic particles are then carried along with the liquid flow. A part of the macroscopic particles is then carried along through the pores in the membrane 16, but macroscopic particles of a magnitude too large for the pores are stopped by the membrane 16 and do no longer flow along with the liquid.
The .contact between the liquid and the membrane 16 makes it possible for ions of the membrane to selectively dissolve and/or selectively precipitate on the membrane 16. For instance, on the surface, OH-groups can yield H+ions to the liquid. Due to this type of charge separation, a net charge is formed on the surface of the membrane 16. The net charge generates an electric field, whose field fines run through the liquid.
Fig. 2 shows the field strength of this field as a function of the distance to the membrane 16 in the absence of flow (not to scale). According to the laws of Maxwell, the field strength is proportional to the spatial integral of the charge. At the transition 20 between the area within the membrane and the liquid, a jump in the field strength occurs because of the charge on the surface of the membrane 16. In the liquid, the field strength decreases again because the liquid has a location-dependent net charge. This net charge is formed in that particles with different charges are attracted to and repelled from the membrane, respectively, by the electric field.
The transport of macroscopic particles to and selectively through the membrane 16 occurs in that these particles are carried along by the flow of the liquid. The electric field counteracts the flow of the liquid carrying along charged macroscopic particles through the membrane. Particles having the same charge as the membrane 16 are repelled upstream of the membrane, particles having an opposite charge to the membrane 16 are retained downstream of the membrane. According to the invention, the field that is generated by the net charge on the surface of the membrane 16 is compensated by utilizing a conductive membrane 16 or a membrane 16 with at least one conductive layer and by using the voltage source 18 between the membrane 16 and the electrodes 17a,b and/or the wall of the channel 14. Preferably, to this end, with the voltage source, virtually as much, but opposite, charge is introduced into the membrane or in the conductive layer as there is charge present on the surface of the membrane. As a consequence, the field generated by the charge on the membrane is compensated. This has as a consequence that the membrane does not generate an electric field in the liquid. In principle, the field is already removed by bringing the conductive layer to the same potential as the electrodes 17a,b in the liquid. But depending on the liquid, an improved through-flow effect can be obtained by applying a potential difference between the membrane 16 and the electrodes 17a,b. Further, in principle, the effect of the electric field on the through-flow upstream of the membrane is the strongest. That is why, preferably, in any case upstream of the membrane the field is removed. But without high additional costs, with the conductive membrane 16, the field on both sides of the membrane 16 is removed, leading to optimal through-flow. Preferably, the electrodes 17a,b are then brought to the same potential at both sides of the membrane 16, so that they have the same potential difference relative to the membrane 16 (or both the same potential as the membrane 16).
Fig. 3 shows, in side view, a detail of a cross section of a membrane 16 for use as liquid filter in a device as shown in Fig. 1. The side view contains one single pore 32, but it will be clear that the membrane contains many such pores: one pore has, for instance, a size of 0.5 micrometer, and the distance between different pores can be in the order of magnitude of 10 micrometers, with the membrane having a magnitude of several centimeters. The membrane 16 is made of a ceramic carrier 30, in which photolithographic pores 32 of a particular size have been etched. Thereupon, a conductive layer 34 is applied onto the surface of the carrier 30, so that the conductive layer 34 also continues into the pores. Consequently, in the pores as well, no fields are formed as a result of surface charge on the membrane, and, there as well, the through-flow of the macroscopic particles is not hindered by an electric field. For certain membrane-liquid combinations for that matter, the field in the pores 32 will not be objectionable. In that case, the conductive layer 34 in the pores can be omitted, for instance by first applying the conductive layer 34 onto the Garrier 30 and then etching the pores, or conversely, by selecting a deposition technique which only covers the surface of the membrane and not the inside of the pore.

Claims

Claims
1. A method for selectively filtering particles according to size from a liquid, wherein
- the liquid is guided through a flow channel,
- the liquid is guided through pores, selecting according to size, in a membrane in the flow channel, which membrane comprises a conductive layer;
- with a voltage source, a potential difference is applied between the conductive layer and an electrode in the flow channel or in a wall of the flow channel, with which an electric field in the liquid resulting from a net charge on a surface of the membrane as a result of ion exchange between the liquid and the membrane is substantially compensated.
2. A method according to claim 1, wherein both upstream and downstream of the membrane electrodes are included in the flow channel or in a wall of the flow channel, the potential of the electrodes on both sides of the membrane having the same potential.
3. A liquid filtering device provided with
- a flow channel for a liquid flow;
- a membrane provided with pores, which membrane comprises at least one conductive layer and which membrane is included in the flow channel such that in use, the liquid flow runs through the pores; - an electrode in the flow channel and/or on a wall of the flow channel;
- a voltage source electrically coupled between the conductive layer and the electrode, and arranged for applying a potential difference between the conductive layer and the electrode, so that an electric field resulting from a net charge on the membrane as a result of ion exchange between the liquid and the membrane is at least substantially eliminated.
4. A liquid filtering device according to claim 3, wherein the electrode is included upstream in the flow channel and/or on the wall of the flow channel.
5. A liquid filtering device according to claim 4, provided with a further electrode downstream in the flow channel and/or on the wall of the flow channel, wherein the voltage source is coupled to the further electrode for bringing the electrode and the further electrode to the same potential.
6. A liquid filtering device according to any one of the preceding claims, wherein the potential difference is smaller than a potential difference above which electrolysis occurs between the liquid and the membrane and/or the electrode.
7. " A liquid filtering device according to any one of the preceding claims, wherein all pores have virtually the same size from a range between one-tenth of a micrometer and ten micrometers.
8. A liquid filtering device according to any one of the preceding claims, wherein the membrane is manufactured from a ceramic material which, an inner wall of the pores included, is covered with a conductive layer.
9. A membrane for use in a liquid filtering device according to claim 8.
PCT/NL2003/000204 2002-03-19 2003-03-19 Method of filtering particules from a liquid, liquid filtering device and membrane WO2003078036A1 (en)

Priority Applications (1)

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NL1020204 2002-03-19
NL1020204A NL1020204C2 (en) 2002-03-19 2002-03-19 Method for filtering particles from a liquid and liquid filter device.

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