WO2000064578A1

WO2000064578A1 - Combined magnetite and activated carbon filters for purifying a fluid stream

Info

Publication number: WO2000064578A1
Application number: PCT/US2000/010805
Authority: WO
Inventors: Marit Jagtoyen; P. Gail M. Brion
Original assignee: University Of Kentucky Research Foundation
Priority date: 1999-04-23
Filing date: 2000-04-20
Publication date: 2000-11-02
Also published as: AU4480500A

Abstract

A filter and method are provided for purifying a fluid stream such as a drinking water stream or breathable air stream. The filter comprises an active agent of adsorbent materials including a substantially uniform mixture of magnetite and activated carbon (fibers preferentially) in a composite structure. The method involves passing a contaminated fluid stream through the filter, adsorbing and entrapping contaminants on the surfaces of the magnetite particles and activated carbon and recovering the decontaminated fluid stream.

Description

COMBINED MAGNETITE AND ACTIVATED CARBON FILTERS FOR PURIFYING A FLUID STREAM

Technical Field

This invention relates generally to the field of filters and methods useful in adsorbing organics, disinfection by-products, lead and other metals, chlorine, viruses and bacteria from fluid streams such as drinking water and breathable air supplies.

Background of the Invention

The rapidly expanding world population and the adverse environmental effects from the by-products of continued industrialization have made it increasingly more difficult to reliably provide the necessary supply of drinking water. Similarly, many industrial processes pollute the air with noxious and toxic by-products. In enclosed areas of certain plants and industrial facilities, the ambient air must first be cleaned to provide a safe and breathable air supply.

To date, a multitude of approaches have been proposed to clarify, purify and or filter drinking water and air streams. While many are effective for their intended purpose and many often incorporate active ingredients providing high selective absorption or adsorption of a particular target contaminant, further improvements in filtering technology are desired. In particular, filters for effectively filtering a wide range of contaminants including various microbial pathogens, disinfection byproducts and organic substances are needed.

Summary of the Invention

In accordance with the purposes of the present invention as described herein, a filter is provided for purifying a fluid stream including, but not limited to, a drinking water supply and a breathable air supply. The filter broadly comprises an active agent of adsorbent materials including a uniform mixture of finely ground magnetite and activated carbon fibers or activated carbon granules or powder.

More preferably, an activated composite filter is provided for purifying a fluid stream. The activated composite filter comprises an active agent including an effective amount of a mixture of magnetite and activated carbon adsorbent materials and a binder for binding the active adsorbent agent together as a composite filter.

More specifically, the magnetite is in the form of magnetite particles having a size of between substantially lμm - 1mm. Additionally, the activated carbon is in the form of fibers having an average length of between substantially 0.1 - 0.4 mm and an average width of between substantially 5 - 100 μm. Additionally, the activated carbon and the magnetite may be provided in a weight ratio of between substantially 19:1 and 1 :1. Further, the filter has a cured density of between substantially 0.2 - 0.75 g/cc and an activated density of between substantially 0.1 - 0.55 g/cc. The activated carbon in the filter undergoes a burnoff of between substantially 0-80% during activation and provides a BET surface area of 300-2000 m²/g after activation. In accordance with yet another aspect of the present invention, a method is provided for purifying a fluid stream by passing that fluid stream through a filter of the nature just described.

Advantageously, the resulting filter and method function to remove microbial pathogens such as viruses, bacteria and cysts from a fluid stream with extremely high efficiency. Additionally, the mixing of the magnetite and activated carbon may advantageously function to deter subsequent desorption of the microbial pathogens as well as the disinfection byproducts and organic substances. This unforseen synergistic effect produced by the present invention represents a significant advance in the filtering art.

The addition of magnetite to the carbon fiber filter matrix results in greater electrical conductance of the material due to bridging effects caused by the presence of the magnetite particles at the junctures of the fibers. Enhanced conductivity of the resultant filter can allow for resistance generated heating. Heat is a well-known method for inactivating microorganisms and the enhanced conductance provides an opportunity for more uniform heating. The utilization of the enhanced conductance of the material for heat inactivation of adsorbed microorganisms and purging of volatile compounds is readily apparent.

The following description shows and describes a preferred embodiment of this invention, simply by way of illustration of one of the modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive. Brief Description of the Drawing

The accompanying drawing incorporated in and forming a part of the specification, illustrates several aspects of the present invention and together with the description serves to explain the principles of the invention.

Figures la-e are five SEM micrographs combined in each case with an elemental map of the distribution of magnetite particles throughout the carbon fiber structure. The micrographs are cross sections taken at five different positions in the same carbon fiber-magnetite composite. These micrographs demonstrate the substantially uniform distribution of magnetite throughout the carbon fiber composite structure;

Figure 2 is a graphical representation illustrating the adsorption of E.coli on activated carbon composite filters produced with and without magnetite; and

Figure 3 is a graphical representation illustrating removal of E.coli on activated carbon fiber composite filters produced with and without magnetite.

Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawing.

Detailed Description of the Invention

Reference is now made to the SEM micrographs of Figure la-e showing the filter of the present invention for purifying a fluid stream. Exemplary fluid streams capable of purification utilizing the filter of the present invention include a drinking water supply stream and a breathable air stream. It should be appreciated, however, that other fluid streams could be clarified/purified/filtered in accordance with the teachings of the present invention.

The filter of the present invention comprises an active agent of adsorbent materials including a true mixture of magnetite or Fe₃0₄ and activated carbon. In one embodiment, the filter is a composite filter incorporating an effective amount of a uniform mixture of magnetite and activated carbon adsorbent materials in conjunction with a binder for binding the active agent together as a composite filter. Preferably, the activated carbon is in the form of fibers, the fiber or fibers selected depend upon the ultimate use of the resulting composite.

The manufacture of pitch based fibers is well known in the art and is briefly described herein. Pitch is conventionally derived from coal tar or from a heavy petroleum fraction. Fiber forming methods include melt spinning and melt blowing. During both of these processes, the pitch is carefully heated to control the viscosity and then forced through a number of fine orifices to produce fibers as the pitch resolidifies. In the spinning process, the fiber diameter is controlled by continuously drawing the fibers down and winding them onto a reel as they form. The blowing process employs a stream of gas which alternates and draws the fibers down when they are extended through orifices. They are then blown onto a moving belt to form a random mat of "green" pitch fibers. In both methods, extreme care must be taken to control the temperature and other conditions. Once formed, the green fibers are "stabilized", by heating the fibers in an oxidizing atmosphere, so that they are rendered thermosetting and will retain their fibrous form at the high temperatures used in the subsequent carbonization step. After carbonization in an inert atmosphere, the fiber mats contain about 95% carbon by weight.

Preferably, magnetite particles having a size of between approximately lμm - 1mm and activated carbon fibers having an average length of between substantially 0.1 -0.4mm and an average width of between substantially 5-100 μm are mixed in a water slurry with a carbonizable organic powder such as pitch, thermosetting resin or phenolic resin which functions as a binder.

In the preferred forming method the slurry is transferred to a molding tank of any cross section (circular, to make cylinders or blocks or annular to make tubes). The mold has a screen at the bottom. The slurry is filtered through this screen by applying an overpressure of air or applying a vacuum on the drainage side of the screen. In most cases, an acceptable rate of filtration is achieved by relying upon the hydraulic head. Of course, other molding methods can be utilized (e.g. pressure forming or any of the other various forming methods practiced in the plastic's industry).

The resulting green form is partially dried, preferably in air at approximately 50 °C. The form is then removed from the mold and the green form is then cured ( at e.g. 130°C in air) to produce a cured monolithic body. The resulting composite is then carbonized under an inert gas. Preferably, carbonization is conducted for up to 3 hours under nitrogen at 650 °C to pyrolyze the resin binder. More complete details relating to forming methods that may be utilized are set forth in pending U.S. patent application serial no. 08/747,109 to Burchell et al. and issued U.S. Patent 5,972,253 to Kimber, the full disclosures of which are incorporated herein by reference.

The composite formed by the above process defines voids between the magnetite particles and fibers which allow free flow of fluid through the material and ready access to the magnetite and carbon fiber surfaces. Further, the individual magnetite particles and carbon fibers are held in place by the pyrolyzed resin binder and thus cannot move or settle due to the flow of gases/liquids through the material. Following its manufacture, the carbon fiber composite filter is activated. Activation of the carbon fibers is accomplished by reaction with steam, carbon dioxide, or by chemical activation. The resulting chemical reactions remove carbon and develop pores in the carbon fibers which are classified by diameter: micropores (less than 2nm), mesopores (2-50nm) and macropores (greater than 50nm).

In the preferred embodiment, the composite is steam activated in a steam/nitrogen atmosphere. The preferred activation conditions are 800- 950°C, steam at a partial pressure of 0.1-0.9 atmosphere and for durations of 1-3 hours. The activation conditions may, of course, be varied by changing the activation gas, its concentration, the flow rate, the temperature and the optional presence of a catalyst to influence total surface area and pore size distribution. Further, the use of post activation treatments can be implemented. For example, further heating in a controlled gas atmosphere or the introduction of chemicals could affect the pore size distribution and surface chemistry. Once carbonized or activated, the composite can be machined to any desired shape, forming a monolithic carbon fiber composite.

The activated carbon and magnetite are provided in the mixture at a weight ratio of between substantially 19: 1 to 1 : 1. Additionally, in one embodiment the fibers in the composite undergo a burnoff of between substantially 0-80% during activation and the filter has a cured density after carbonization but before activation of between substantially 0.2 - 0.75 g/cc and an activated density of between substantially 0.1 - 0.55 g/cc following activation. Thus, the composite filter of the present invention has a ratio of cured density to activated density of between substantially 1.8:1 to 1.1 :1. Further, the BET surface area of the activated composite filter is preferably between substantially 300-2000 m²/g.

In accordance with another aspect to the present invention, the composite formed by the above process includes voids between the fibers and the magnetite particles which allow free flow of fluid through the material and therefore, ready access to the carbon fiber and magnetite particle surfaces. As noted above, the individual magnetite particles and carbon fibers are, of course, held in place by the pyrolyzed resin binder and thus cannot move or settle due to the flow of gases or liquids through the material.

The composite filters in one embodiment include a void volume between substantially 63.2-94.7% and most specifically between substantially 70.9-81.1%. The resulting composite filter is replete with extensive tortuous pathways running through its body. Viruses, bacteria, cysts, organics and other contaminants in the fluid must pass along and follow these pathways. Generally, bacteria are larger than the pores in the activated carbon and it is the open structure (i.e. large interstices/pathways) of the present filters that allow entry of the bacteria inside the composite and access to the surfaces of the activated carbon fiber that define the boundaries of those interstices/pathways on which the bacteria are effectively trapped. It should also be appreciated that the binder mainly binds the fibers at the intersections of one fiber with another fiber or a magnetite particle. Accordingly, most of each fiber's surface pores are maintained accessible for adsorption of organics, bacteria, cysts, viruses and other contaminants. While the viruses are also generally too large to become entrapped in the pores, they do become entrapped on the extensive external carbon fiber surfaces and magnetite particle surfaces that define the tortuous pathways characteristic of the composite structure. Accordingly, the filtering efficiency provided by the composite filter of the present invention is significantly enhanced over any activated carbon filter heretofore available in the art. Most significantly, the combination of magnetite particles and activated carbon significantly improves the retention of bacteria within the filter. Additionally, the addition of magnetite significantly improves the removal of metals from water and adds to the ease of material handling. Magnetic metals, such as iron, are now captured by the magnetic properties of the magnetite and are held in the composite filter.

In accordance with another aspect of the present invention, a method ofpurifying a fluid stream is provided. That method comprises passing a contaminated fluid stream through a filter including as an active agent adsorbent materials including a substantially uniform mixture of magnetite and activated carbon. The method further includes adsorbing and entrapping the contaminants, encysted protozoa and microbial pathogens such as viruses, bacteria and cysts on the surfaces of the magnetite particles and activated carbon. This is followed by the step of recovering a purified fluid stream.

The following examples further illustrate the invention but it is not to be considered as limited thereto.

Experiment to show substantiallv uniform mixture of magnetite particles and activated carbon fibers: 12 g of P400 pitch based carbon fibers were mixed by a mechanical stirrer with 90 cc of water. 1.1 g of magnetite was mixed in and 3 g of phenolic resin was added to the mixture. The slurry was poured into a mold and air blown for 2 minutes with a flow rate of 15 liters per minute at 3 psi to drive the water out. The composite was ejected from the mold, and cured at 200 °C for 3 hours. The density of the material was 0.240 g/cc.

The cured composite was then activated in steam at 850 C for 2 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 60-70 cc/ hour. The burnoff was 47%. The BET surface area of the material was l l79 m²/g.

The sample was cut up into 5 slices and each slice was examined in a Scanning Electron Microscope (SEM). The SEM micrographs and the corresponding elemental analysis showed that the carbon fiber composite had particles of magnetite distributed uniformly throughout the composite structure. The magnetite particles were trapped in the interstices between the fibers and also stuck to the carbon fiber surfaces.

Examples 1-12 illustrate the process of making an activated carbon fiber composite material of the present invention and its use for bacterial removal. Common practice is to use a surrogate bacteria such as

Escherichia coli (E. Colt) for proof of concept. The examples show that the composite filter of the present invention has excellent capacity for adsorbing bacteria. The data are given in Tables 1-3 and shown in Figures 2 & 3 and illustrate that the activated carbon fiber composite material of the present invention incorporating magnetite particles exhibits an enhanced capacity for removing bacteria from water when compared to activated carbon fiber composites without magnetite particles.

The following examples compare virus and bacteria adsorption and retention for the composite filters of the present invention incorporating a mixture of magnetite particles and activated carbon fibers versus filters incorporating only activated carbon fibers. In all comparative examples, the carbon fibers are from the same production run.

Example 1 :

This composite contains 10% by weight of magnetite to carbon fiber.

The production method for this material involved mixing 26 g of P200 pitch-based carbon fibers (R303T) with 120 cc of water, 2.6 g magnetite and 6.5 g of Durez 2-step phenolic resin. After mixing, the slurry was poured into a one inch diameter cylindrical mold. The mixture was allowed to settle for 10 seconds before applying a vacuum for 1 min to draw the water through the cake and effect partial drying as the fiber-resin mixture adapted to the mold shape. The composite was ejected from the mold, and cured at 200 °C for 3 hours. The cured weight was 31.16 g. The density of the cured composite was 0.629 g/cc.

The cured composite was then activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 29.2%. The BET surface area of the material was 911 m²/g. The activated density of the material was 0.495g/cc.

An adsorption column was made up from the 3.54" long sample with a diameter of 0.98". The weight of the sample was 19.83 g. The column was tested for E. Coli adsorption at a flow rate of 308 ml/hr (or 7.09 col vol/hr) of water spiked with 9.1 X 10⁵ cfu of E. Coli. The removal of E. Coli was better than 4 logs (99.99%) for 3 hours, and two logs (99.5%) in the fourth hour. Detailed results and conditions of the bacteria adsorption test are shown in Table 1.

Example 2:

This composite was made by the same procedure as described for the column in Example 1. It contains 10% by weight of magnetite. It was made from 28 g of P200 pitch-based carbon fibers (R303T) , 120 cc of water and 7g of Durez 2-step phenolic resin. The density of the cured composite was 0.553 g/cc.

The cured composite was activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 26.6%. The BET surface area of the material was 856 m²/g. The density of the material was 0.435 g/cc.

An adsorption column was made up from the 3.464" long, 0.976" diameter sample. The weight of the sample was 18.60 g. The column was tested for E. Coli adsorption at a flow rate of 324 ml/hr (or 7.09 col vol/hr) of water spiked with 9.1 X 10⁵ cfu of E.Coli. The removal of E. Coli was better than 4 logs (99.99%) for 2 hours, and one log (98.9%) in the third hour. Detailed results and conditions of the bacteria adsorption test are shown above in Table 1.

Example 3:

This composite contained 5% by weight of magnetite to carbon fiber. The production method involved mixing 26 g of P200 pitch based carbon fibers(R303T) with 120 cc of water, 1.3 g magnetite and 6.5 g of Durez 2- step phenolic resin. After mixing, the slurry was poured in a mold made from a 1" ID PVC tube, with a perforated stainless steel screen at the bottom. The mixture was allowed to settle for 10 seconds before applying a vacuum for 1 min to draw the water through the cake and effect partial drying as the fiber-resin mixture adapted to the mold shape. The composite was ejected from the mold, and cured at 200 °C for 3 hours. The density of the cured composite was 0.582 g/cc.

The cured composite was then activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 30.9%. The BET surface area of the material was 948 m²/g. The density of the activated material was 0.438 g/cc. An adsorption column was made up from the 3.52" long sample with a diameter of 0.98". The weight of the sample was 18.87 g. The column was tested for E.Coli adsorption at a flow rate of 330 ml/hr (or 7.09 col vol/hr) of water spiked with 1.1 X 10⁶ cfu of E.Coli. The removal of E.Coli was better than 4 logs (99.998%) for 3 hours, and one log (93.9%) in the fourth hour. Detailed results and conditions of the bacteria adsorption test are shown in Table 1.

Example 4:

This composite was made by the same procedure as described for the column of Example 3. It contained 5% by weight of magnetite. It was made from 28 g of P200 pitch-based carbon fibers (R303T) , 120 cc of water and

7g of Durez 2-step phenolic resin. The density of the cured composite was

0.60 g/cc.

The cured composite was activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 35.7%. The BET surface area of the material was

1050 m²/g. The density of the activated composite was 0.425 g/cc. An adsorption column was made up from the 3.60" long, 0.976" diameter sample. The weight of the sample was 18.70 g. The column was tested for E.Coli adsorption at a flow rate of 332 ml/hr (or 7.09 col vol/hr) of water spiked with 1.1 X 10⁶ cfu/ml of E.Coli. The removal of E.Coli was better than 4 logs (99.99%) for 3 hours, and two logs (99.45%) in the third hour. Detailed results and conditions of the bacteria adsorption test are shown in Table 1.

Example 5:

This column was made from two different composites, both which contained 25% by weight of magnetite to carbon fiber. The production method involved mixing 26 g of P200 pitch-based carbon fibers (R303T) with 120 cc of water, 2.6 g magnetite and 6.5 g of Durez 2-step phenolic resin. After mixing, the slurry was poured in a mold made from a 1" ID PVC tube, with a perforated stainless steel screen at the bottom. The mixture was allowed to settle for 10 seconds before applying a vacuum for 1 min to draw the water through the cake and effect partial drying as the fiber- resin mixture adapted to the mold shape. The composite was ejected from the mold, and cured at 200 °C for 3 hours. The density of the cured composite was 0.593 g/cc for the first sample and 0.603 g/cc for the second sample.

The cured composites were then activated in steam at 877° C for 1.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 26.7% for the first sample and 25.9% for the second sample. The density of the activated materials were 0.471 and 0.482 g/cc respectively. The BET surface area of the materials were 857 and 840 m²/g respectively. An adsorption column was made up from the two samples, the length of the column was 3.61" with a diameter of 0.98". The weight of the combined sample was 21.54 g. The column was tested for E. Coli adsorption at a flow rate of 324 ml/hr (or 7.09 col vol/hr) of water spiked with 1.4 X 10° cfu ml of E. Coli. The removal of E. Coli was better than 4 logs

(99.9998%) for 5 hours. Detailed results and conditions of the bacteria adsorption test are shown in Table 1.

Example 6:

This composite contained 25% by weight of magnetite to carbon fiber. The production method involved mixing 26 g of P200 pitch based carbon fibers(R303T) with 120 cc of water, 6.5 g magnetite and 6.5 g of Durez 2-step phenolic resin. After mixing, the slurry was poured in a mold made from a 1" ID PVC tube, with a perforated stainless steel screen at the bottom. The mixture was allowed to settle for 10 seconds before applying a vacuum for 1 min to draw the water through the cake and effect partial drying as the fiber-resin mixture adapted to the mold shape. The composite was ejected from the mold, and cured at 200°C for 3 hours. The density of the cured composite was 0.605 g/cc.

The cured composite was then activated in steam at 877° C for 1.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 25.8%. The BET surface area of the material was 839 m²/g. The density of the activated material was 0.483 g/cc. An adsorption column was made up from the 3.60" long sample with a diameter of 0.982". The weight of the sample was 22.06 g. The column was tested for E. Coli adsorption at a flow rate of 318 ml/hr (or 7.09 col vol/hr) of water spiked with 1.4 X 10⁶ cfu of E.Coli. The removal of E.Coli was better than 4 logs (99.998%) for 5 hours, and 2 logs in the 6th hour. Detailed results and conditions of the bacteria adsorption test are shown in Table 1.

Example 7: The column to be tested was cut from a 4" diameter cylindrical block of carbon fiber composite. Three hundred grams of P200 pitch-based carbon fibers (R303T) were mixed with 3000 cc of water and 75 g of Durez 7716 2-step phenolic resin. After mixing for 5 minutes, the slurry was poured into a 4" diameter cylindrical mold where the fiber-resin mixture adapted to the mold shape. The mixture was allowed to settle for ~ 10 seconds before applying a vacuum for 20 min. The composite was ejected from the mold, and cured at 200 °C for 3 hours. The cured weight was 325.68 g. The density of the cured composite was 0.54 g/cc.

The cured composite was then activated in steam at 877° C for 4.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 25.2%. The BET surface area of the material was 550 m²/g.

A column was cut from the block using a drill press fitted with a 1" diameter core extractor. The length of the core was 3.54", the outside diameter was 0.907" and the weight was 15.50 g. The density of material was 0.414g/cc.

The sample was tested for E.Coli adsorption at a flow rate of 328 ml/hr (or 8.78 column volumes per hour) of water spiked with 9.1 X 10⁵ cfu/ml of E. Coli . The removal of E. Coli was better than 5 logs (99.999%) for 1 hour, and 0 logs (82.2%) in the second hour. Detailed results of bacteria adsorption test are shown in Table 2. Example 8:

This column was made from the same material as the column of example 7. The method of making was identical. The burnoff was 25.2%. The BET surface area of the material was 550 m²/g. A column was cut from the block using a drill press fitted with a 1 " diameter core extractor. The length of the core was 3.538", the outside diameter was 0.907" and the weight was 15.42 g. The activated density of material was 0.412g/cc.

The sample was tested for E. Coli adsorption at a flow rate of 320 ml/hr (or 8.54 column volumes per hour) of water spiked with 9.1 X 10⁵ cfu/ml of E.Coli . The removal of E.Coli was better than 5 logs (99.999%) for 1 hour, and one log (95.2%) in the second hour. Detailed results of bacteria adsorption test are shown in Table 2.

Example 9: This composite contained 20% by weight of magnetite to carbon fiber. The production method involved mixing 26 g of P200 pitch based carbon fibers (R303T) with 120 cc of water, 5.2 g magnetite and 6.5 g of Durez 2-step phenolic resin. After mixing, the slurry was poured in a mold made from a 1" ID PVC tube, with a perforated stainless steel screen at the bottom. The mixture was allowed to settle for 10 seconds before applying a vacuum for 1 min to draw the water through the cake and effect partial drying as the fiber-resin mixture adapts to the mold shape. The composite was ejected from the mold, and cured at 200 °C for 3 hours. The density of the cured composite was 0.651 g/cc. The cured composite was then activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 27.7%. The BET surface area of the material was 879 m²/g. The density of the activated material was 0.517 g/cc. An adsorption column was made up from the 3.33" long sample with a diameter of 0.98". The weight of the sample was 21.11 g. The column was tested for E.Coli adsorption at a flow rate of 3000 ml/hr (or 7.09 col vol/hr) of water spiked with 1.1 X 10⁶ cfu of e-coli. The removal of e-coli was better than 4 logs (99.998%) for the first 5 minutes, and 3 logs (99.95%) after 9.5 minutes. The adsorption was stopped at this point, before breakthrough was reached. Detailed results and conditions of the bacteria adsorption test are shown in Table 3.

Example 10:

This composite was made by the same procedure as described for the column in example 9. This composite contained 20% by weight of magnetite to carbon fiber. It was made from 26 g of P200 pitch-based carbon fibers (R303T) , 120 cc of water, 5.2 g magnetite and 6.5 g of Durez

2-step phenolic resin. The density of the cured composite was 0.631 g/cc. The cured composite was then activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 26.0%. The BET surface area of the material was 842 m²/g. The density of the material was 0.517 g/cc.

An adsorption column was made up from the 3.67" long sample with a diameter of 0.98". The weight of the sample was 23.22 g. The column was tested for e-coli adsorption at a flow rate of 3000 ml/hr (or 7.09 col vol/hr) of water spiked with 1.1 X 10⁶ cfu of e-coli. The column was found to leak, so the data was not evaluated but it is included in Table 3 for continuity of record.

Example 11 :

The production method for this sample is the same as that for the column in Example 9. It was made from 24 g of P200 pitch-based carbon fibers (R303T) , 120 cc of water and 6g of Durez 2-step phenolic resin. The density of the cured composite was 0.52 g/cc.

The cured composite was then activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 3.2 liters per minute and a water flow rate of 160 cc/ hour. The burnoff was 21.3 %. The BET surface area of the material was 743 m²/g. The density of activated material was 0.437 g/cc.

An adsorption column was made up from a 3.66" long composite of diameter 0.975" weighing 19.57 g. The sample was tested for E.Coli adsorption at a high flow rate of 3000 ml/hr (or 67.0 column volumes per hour) of water spiked with 9.1 X 10⁵ cfu/ml of E.Coli . The removal of E.Coli was better than 3 logs (99.97%) for 5 minutes. The adsorption was stopped after 10 minutes, before saturation was reached. Detailed results and conditions of the E.Coli adsorption test are shown in Table 3.

Example 12:

The production method for this sample is the same as that for the column in example 11. It was made from 24 g of P200 pitch-based carbon fibers (R303T) , 120 cc of water and 6g of Durez 2-step phenolic resin. The density of the cured composite was 0.52 g/cc.

The cured composite was then activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 3.2 liters per minute and a water flow rate of 160 cc/ hour. The burnoff was 21.9 %. The BET surface area of the material was 755 m /g. The density of the material was 0.418 g/cc.

An adsorption column was made up from a 3.69" long composite of diameter 0.999" weighing 19.79 g. The sample was tested for E.Coli adsorption at a high flow rate of 3000 ml/hr (or 63.3 column volumes per hour) of water spiked with 9.1 X 10⁵ cfu/ml of E.Coli . The removal of E. Coli was better than 4 logs (99.99%) for 5 minutes. The adsorption was stopped after 10 minutes, before saturation was reached. Detailed results and conditions of E.Coli adsorption test are shown in Table 3.

Examples 13-26 describe the process of making composite materials with different amounts of magnetite and the use of the resulting composite filters for the removal of MS2 virus from water. The data from these examples is summarized in Tables 4 and 5. Tables 4 and 5 show that the addition of up to 25% magnetite gives up to 5 logs of removal of viruses measured by the bacteriophage MS-2. In the range of virus concentrations tested both materials performed admirably. A clear distinction cannot be made between the two materials without testing at unreasonably high virus titers.

Example 13: This composite contained 10% by weight of magnetite to carbon fiber. The production method for this material involved mixing 26 g of P200 pitch-based carbon fibers (R303T) with 120 cc of water, 2.6 g magnetite and 6.5 g of Durez 2-step phenolic resin. After mixing, the slurry was poured in a mold made from a 1" ID PVC tube, with a perforated stainless steel screen at the bottom. The mixture was allowed to settle for 10 seconds before applying a vacuum for 1 min to draw the water through the cake and effect partial drying as the fiber-resin mixture adapts to the mold shape. The composite was ejected from the mold, and cured at 200 °C for 3 hours. The density of the cured composite was 0.631 g/cc. The cured composite was then activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 29.2%. The BET surface area of the material was 911 m²/g. The density of the activated material was 0.485 g/cc.

An adsorption column was made up from the 3.68" long sample with a diameter of 0.98". The weight of the sample was 21.86 g. The column was tested for MS2 virus adsorption at a flow rate of 330 ml/hr (or 7.09 col vol/hr) of water spiked with 1.4 X 10⁶ pfu/ml of MS2. The removal of MS2 was better than 4 logs (99.998%) for 4 hours, and 3 logs (99.9%) in the sixth hour. Inexplicably, the concentration of virus increased in the stock and, accordingly, the data after 6 hours are therefore not reliable. Detailed results and conditions of the virus adsorption test are shown in Table 4.

Example 14:

This composite was made by the same procedure as described for the column in example 13. It contained 10% by weight of magnetite. It was made from 26 g of P200 pitch-based carbon fibers (R303T) , 120 cc of water , 2.6 g magnetite, and 6.5 g of Durez 2-step phenolic resin. The density of the cured composite was 0.567 g/cc.

The cured composite was activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 31.1%. The BET surface area of the material was

952 m²/g. The density of the activated material was 0.434 g/cc. An adsorption column was made up from the 3.853" long, 0.976" diameter sample. The weight of the sample was 20.47 g. The column was tested for MS2 virus adsorption at a flow rate of 318 ml/hr (or 7.09 col vol/hr) of water spiked with 1.4 X 10⁶ pfu/ml of MS2. The removal of MS2 was better than 4 logs (99.998%) for 9 hours, and 3 logs (99.97%) in the tenth hour, at which point the experiment was concluded. It is possible that the column would have lasted longer. Detailed results and conditions of the virus adsorption test are shown in Table 4.

Example 15: This composite contains 25% by weight of magnetite to carbon fiber. The production method involved mixing 26 g of P200 pitch based carbon fibers(R303T) with 120 cc of water, 6.5 g magnetite and 6.5 g of Durez 2-step phenolic resin. After mixing, the slurry was poured in a mold made from a 1" ID PVC tube, with a perforated stainless steel screen at the bottom. The mixture was allowed to settle for 10 seconds before applying a vacuum for 1 min to draw the water through the cake and effect partial drying as the fiber-resin mixture adapted to the mold shape. The composite was ejected from the mold, and cured at 200 °C for 3 hours. The density of the cured composite was 0.660 g/cc. The cured composite was then activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 25.7%. The BET surface area of the material was 837 m²/g. The density of the activated material was 0.540 g/cc. An adsorption column was made up from the 3.62" long sample with a diameter of 0.98". The weight of the sample was 23.95 g. The column was tested for MS2 virus adsorption at a flow rate of 308 ml/hr (or 7.09 col vol/hr) of water spiked with 1.7 X 10⁷ pfu/ml of MS2. The removal of MS2 was better than 51ogs (99.999%) for 10 hours, at which point the experiment was concluded. It is possible that the column would have lasted longer. Detailed results and conditions of the virus adsorption test are shown in Table 4.

Example 16:

This composite was made by the same procedure as described for the column of example 15. It contains 25% by weight of magnetite. It was made from 26 g of P200 pitch-based carbon fibers (R303T) , 120 cc of water , 6.5 g magnetite, and 6.5 g of Durez 2-step phenolic resin. The density of the cured composite was 0.696 g/cc.

The cured composite was then activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 32.8%. The BET surface area of the material was 988 m²/g. The density of the activated material was 0.514 g/cc.

An adsorption column was made up from the 3.76" long sample with a diameter of 0.98". The weight of the sample was 23.67 g. The column was tested for MS2 virus adsorption at a flow rate of 330 ml/hr (or 7.09 col vol/hr) of water spiked with 1.7 X 10⁷ pfu/ml of MS2. The removal of MS2 was better than 51ogs (99.999%) for 10 hours, at which point the experiment was concluded. It is possible that the column would have lasted longer. Detailed results and conditions of the virus adsorption test are shown in Table 4.

Example 17: The column to be tested was cut from a 4" diameter cylindrical block of carbon fiber composite. Three hundred grams of P200 pitch-based carbon fibers (R303T) were mixed with 3000 cc of water and 75 g of Durez 7716 2-step phenolic resin. After mixing for 5 minutes, the slurry was poured into a 4" diameter cylindrical mold where the fiber-resin mixture adapts to the mold shape. The mixture was allowed to settle for ~ 10 seconds before applying a vacuum for 20 min. The composite was ejected from the mold, and cured at 200 °C for 3 hours. The cured weight was 325.68 g. The density of the cured composite was 0.54 g/cc. This material was made by pouring all the mixture in the mold simultaneously, not in increments, giving less time for the fibers to settle and creating a composite that is not layered.

A column was cut from the block using a drill press fitted with a 1" diameter core extractor. The length of the core was 3.50", the outside diameter was 0.907" and the weight was 15.96 g. The density of the activated material was 0.43 lg/cc. The sample was tested for MS2 virus adsorption at a flow rate of 330 ml/hr (8.91 column volumes/hr) of water spiked with 1.4 X 10⁷ pfu/ml of MS2. The removal of MS2 was better than 99.999% for 9 hours, 99.997 % in the tenth hour. Detailed results of virus adsorption tests are shown in Table 4.

Example 18:

This column was made from the same material as the column of example 17. The method of making was identical. The burnoff was 25.2%. The BET surface area of the material was 550 m²/g.

A column was cut from the block using a drill press fitted with a 1" diameter core extractor. The length of the core was 3.538", the outside diameter was 0.907" and the weight was 15.44 g. The density of the activated material was 0.417g/cc.

The sample was tested for MS2 virus adsorption at a flow rate of 330 ml/hr (8.88 column volumes/hr) of water spiked with 1.4 X 10⁷ pfu/ml of MS2. The removal of MS2 was better than 99.9998% for 10 hours. Detailed results of virus adsorption tests are shown in Table 4.

Example 19:

This composite contained 10% by weight of magnetite to carbon fiber. The production method for this material involved mixing 26 g of P200 pitch-based carbon fibers (R303T) with 120 cc of water, 2.6 g magnetite and 6.5 g of Durez 2-step phenolic resin. After mixing, the slurry was poured in a mold made from a 1" ID PVC tube, with a perforated stainless steel screen at the bottom. The mixture was allowed to settle for 10 seconds before applying a vacuum for 1 min to draw the water through the cake and effect partial drying as the fiber-resin mixture adapted to the mold shape. The composite was ejected from the mold, and cured at 200 °C for 3 hours. The density of the cured composite was 0.632 g/cc.

The cured composite was then activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 32.6 %. The BET surface area of the material was 983 m²/g. The density of the activated material was 0.466 g/cc. An adsorption column was made up from the 3.66" long sample with a diameter of 0.98". The weight of the sample was 20.90 g. The column was tested for MS2 virus adsorption at a flow rate of 3000 ml/hr (or 7.09 col vol/hr) of water spiked with 3.3 X 10⁷ pfu/ml of MS2. The removal of MS2 was better than 4 logs (99.99%) for the first 60 minutes of the run, it then dropped to one log (98.71 %) in the next ten minutes. Detailed results and conditions of the virus adsorption test are shown in Table 5.

Example 20:

This composite was made by the same procedure as described for the column of example 13. It contained 10% by weight of magnetite. It was made from 26 g of P200 pitch-based carbon fibers (R303T) , 120 cc of water , 2.6 g magnetite, and 6.5 g of Durez 2-step phenolic resin. The density of the cured composite was 0.635 g/cc.

The cured composite was then activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 31.4 %. The BET surface area of the material was 958 m²/g. The density of the activated material was 0.467 g/cc. An adsorption column was made up from the 3.54" long sample with a diameter of 0.98". The weight of the sample was 20.24 g. The column was tested for MS2 virus adsorption at a flow rate of 3000 ml/hr (or 7.09 col vol/hr) of water spiked with 3.3 X 10⁷ pfu/ml of MS2. The removal of MS2 was better than 5 logs (99.999%) for the first 20 minutes of the run, then 4 logs til 30 minutes, then 3 logs til 60 minutes, it then dropped to one log

(96.60 %) in the next ten minutes. Detailed results and conditions of the virus adsorption test are shown in Table 5.

Example 21 : The production method for this material which is made directly as a 1" diameter, ~ 4" long column involved mixing 28 g of P200 pitch-based carbon fibers (R303T) with 120 cc of water and 7g of Durez 2-step phenolic resin. After mixing, the slurry was poured into a mold made from a 1" ID PVC tube, where the fiber-resin mixture adapted to the mold shape. The mixture was allowed to settle for ~ 10 seconds before applying a vacuum for 1 min to draw the remaining water through the cake and effect partial drying. The composite was ejected from the mold, and cured at 200 °C for 3 hours. The cured weight was 31.12 g. The density of the cured composite was 0.548 g/cc.

The cured composite was then activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 28.6%. The BET surface area of the material was 898 m²/g. The density of the activated material was 0.427 g/cc. An adsorption column was made up from the 3.79" long, 0.976" diameter sample. The weight of the sample was 19.83 g. The column was tested for MS2 virus adsorption at a high flow rate of 3000 ml/hr (64.60 column volumes/hr) of water spiked with 5.6 X 10⁷ pfu/ml of MS2. The removal of MS2 was better than 5 logs (99.999991%) for 10 min, then 5 logs for the next 10 minutes. The adsorption was stopped after 20 minutes before saturation was reached. Detailed results and conditions of the virus adsorption test are shown in Table 5.

Example 22:

The production method for this sample was similar to that for the column in example 21. It was made from 28 g of P200 pitch-based carbon fibers (R303T) , 120 cc of water and 7g of Durez 2-step phenolic resin. The cured weight was 31.12 g. The density of the cured composite was 0.553 g/cc.

The cured composite was then activated in steam at 877° C for 3.5 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 26.6%. The BET surface area of the material was 856 m²/g. The density of the activated material was 0.435 g/cc.

An adsorption column was made up from the 3.77" long, 0.976" diameter sample. The weight of the sample was 20.12 g. The sample was tested for MS2 virus adsorption at a high flow rate of 3000 ml/hr (64.90 column volumes/hr) of water spiked with 5.6 X 10⁷ pfu/ml of MS2. The removal of MS2 was better than 99.99991% for 10 min, then 5 logs (99.999%) for the next 10 minutes. The adsorption was stopped after 20 minutes before saturation was reached. Detailed results and conditions of virus adsorption test are shown in Table 5.

Example 23:

This composite contained 25% by weight of magnetite to carbon fiber. The production method involved mixing 24 g of P200 pitch based carbon fibers(R303T) with 120 cc of water, 6.0 g magnetite and 6.0 g of Durez 2-step phenolic resin. After mixing, the slurry was poured in a mold made from a 1" ID PVC tube, with a perforated stainless steel screen at the bottom. The mixture was allowed to settle for 10 seconds before applying a vacuum for 1 min to draw the water through the cake and effect partial drying as the fiber-resin mixture adapted to the mold shape. The composite was ejected from the mold, and cured at 200°C for 3 hours. The density of the cured composite was 0.616 g/cc.

The cured composite was then activated in steam at 877° C for 2.75 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 30.3%. The BET surface area of the material was 935 m²/g. The density of the activated material was 0.475 g/cc. An adsorption column was made up from the 3.64" long sample with a diameter of 0.98". The weight of the sample was 21.06 g. The column was tested for MS2 virus adsorption at a flow rate of 3000 ml/hr (or 7.09 col vol/hr) of water spiked with 9.8 X 10⁶ pfu/ml of MS2. The removal of MS2 was better than 4 logs (99.999%) for 20 minutes, at which point the experiment was concluded. Detailed results and conditions of the virus adsorption test are shown in Table 5.

Example 24:

This composite was made by the same procedure as described for the column in example 15. It contained 25% by weight of magnetite. It was made from 24 g of P200 pitch-based carbon fibers (R303T) , 120 cc of water , 6.0 g magnetite, and 6.0 g of Durez 2-step phenolic resin. The density of the cured composite was 0.610 g/cc.

The cured composite was then activated in steam at 877° C for 2.75 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 30.5%. The BET surface area of the material was 939 m²/g. The density of the activated material was 0.474 g/cc. An adsorption column was made up from the 3.67" long sample with a diameter of 0.98". The weight of the sample was 21.03 g. The column was tested for MS2 virus adsorption at a flow rate of 3000 ml/hr (or 7.09 col vol/hr) of water spiked with 9.8 X 10⁶ pfu/ml of MS2. The removal of MS2 was better than 4 logs (99.999%) for 20 minutes, at which point the experiment was concluded. Detailed results and conditions of the virus adsorption test are shown in Table 5.

Example 25:

This composite contained 25% by weight of magnetite to carbon fiber. The production method involved mixing 24 g of P200 pitch based carbon fibers(R303T) with 120 cc of water, 6.0 g magnetite and 6.0 g of Durez 2-step phenolic resin. After mixing, the slurry was poured in a mold made from a 1" ID PVC tube, with a perforated stainless steel screen at the bottom. The mixture was allowed to settle for 10 seconds before applying a vacuum for 1 min to draw the water through the cake and effect partial drying as the fiber-resin mixture adapted to the mold shape. The composite was ejected from the mold, and cured at 200 °C for 3 hours. The density of the cured composite was 0.606 g/cc.

The cured composite was then activated in steam at 877° C for 2.75 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 27.8%. The BET surface area of the material was 881 m²/g. The density of the activated material was 0.486 g/cc. An adsorption column was made up from the 3.76" long sample with a diameter of 0.98". The weight of the sample was 22.13 g. The column was tested for MS2 virus adsorption at a flow rate of 3000 ml/hr (or 7.09 col vol/hr) of water spiked with 3.8 X 10⁶ pfu/ml of MS2. The removal of MS2 was better than 4 logs (99.99%) for 30 minutes, then 3 logs (99.93%) for the next 30 minutes, at which point the experiment was concluded. Detailed results and conditions of the virus adsorption test are shown in Table 5.

Example 26: This composite was made by the same procedure as described for the column in example 15. It contained 25% by weight of magnetite. It was made from 24 g of P200 pitch-based carbon fibers (R303T) , 120 cc of water , 6.0 g magnetite, and 6.0 g of Durez 2-step phenolic resin. The density of the cured composite was 0.611 g/cc. The cured composite was then activated in steam at 877° C for 2.75 hours at a nitrogen flow rate of 2 liters per minute and a water flow rate of 100 cc/ hour. The burnoff was 27.0 %. The BET surface area of the material was 864 m²/g. The density of the activated material was 0.488 g/cc. An adsoφtion column was made up from the 3.59" long sample with a diameter of 0.97". The weight of the sample was 21.51 g. The column was tested for MS2 virus adsoφtion at a flow rate of 3000 ml/hr (or 7.09 col vol/hr) of water spiked with 3.8 X 10⁶ pfu/ml of MS2. The removal of MS2 was better than 4 logs (99.99%) for 45 minutes, then 2 logs (99.88%) for the next 15 minutes, at which point the experiment was concluded. Detailed results and conditions of the virus adsoφtion test are shown in Table 5.

The following examples 27-30 illustrate the method of preparing composite filters for magnetite particles with granular carbon and a binder.

Example 27: 14 g of F-300 granular activated carbon(GAC) were mixed with 80 cc of water. 7 g of Durez 2-step phenolic resin was added to the mixture.

The slurry was poured into a mold and air was blown for 1 hour. The composite was ejected from the mold, and cured at 200 °C for 3 hours. The cured weight was 12.78 g. The cured composite was then carbonized and activated. Example 28:

14 g of F-300 granular activated carbon(GAC) were mixed with 80 cc of water and 2.8 g of magnetite. 7 g of Durez 2-step phenolic resin was added to the mixture. The slurry was poured into a mold and air was blown for ~ 25 minutes. The composite was ejected from the mold, and cured at 200°C for 3 hours. The cured weight was 12.78 g.

The cured composite was then carbonized and activated.

Example 29:

11 g of fine powder activated carbon (A-8982 Norit) were mixed with 80 cc of water and 2.2 g of magnetite. 2.75 g of Durez 2-step phenolic resin was added to the mixture. The slurry was poured into a mold and air was blown for ~ 25 minutes. The composite was ejected from the mold, and cured at 200°C for 3 hours. The cured weight was 12.78 g.

The cured composite was then carbonized and activated.

Example 30:

11 g of fine powder activated carbon (A-8982 Norit) were mixed with 80 cc of water. 2.75 g of Durez 2-step phenolic resin was added to the mixture. The slurry was poured into a mold and air was blown for ~ 25 minutes. The composite was ejected from the mold, and cured at 200 °C for 3 hours. The cured weight was 12.78 g.

The cured composite was then carbonized and activated. 78

33

Table 1 Removal of e coll from water by activated carbon fiber composites with maqnetite

(flow rats 27Q-330m!/hr, varying Inlet concentration of e-cσli from 9 1E+05 to 1 4E+06)

Table 2 Removal of e coli from water by activated carbon fiber composites without magnetite

(flow rate 328ml/ r, inlet concentration of e-coli of 9 1E+05pfu/ml)

Table 3 removal of e-coll from water by activated carbon fiber composites wtt-h and without magnetite

(flow rate 3000 ml/hr(63 67 column vofumes/hr) e-coli concentration 1 Ot≡+OS to 1 4E+D6)

Example 31 :

The cured and activated composites of any of Examples 1-30 are provided in an adsorption column and utilized to filter bacteria, virus and other contammants from an air stream. The electrical resistivity of the activated carbon fiber composites is important for applications where the carbon with adsorbed pathogens needs to be disinfected by heat treatment. By applying a potential across the composites, they can be heated in-situ. Their rate of heating will be determined by the electrical resistivity. The electrical resistivity of samples with different magnetite contents are shown in Table 6. It is obvious that the incorporation of magnetite alters resistivity. In the samples with 10% magnetite incorporation, the resistivity has increased from the non- magnetite containing sample, it is likely that the fibers are pushed apart by the magnetite particles and therefore fiber- fiber contact is diminished, hence resistivity is increased. For the samples with 25% magnetite the resistivity is lower than for the non-containing samples. It is believed that there is now so much magnetite in the sample that there is conduction between magnetite-magnetite interfaces, hence the resistivity is low.

To illustrate the influence of electrical resistivity on heating time, two of the samples were compared by applying IN and 1A across the sample. The sample with 10% magnetite and high resistivity heated to 100 °C in 24 minutes, while the sample with 25% magnetite only reached 30 °C after 24 minutes and only 42 °C after 45 minutes, hence it heats much slower. The slower, more even heating allows for better disinfection of the material.

Table 5ι Etectricai resisiivixy of activated carbon fiber composites wi-h different magnetite content

Sampie Magnetite burnoff density resistivity

(g/cc) (ohm-cm)

3=1 31 1 0 38 0.30 0.23

Me 2 1 0 23 0 ,29 0.45 el 1 Q 26 0.30 0.55

Me 51 25 26 0.47 0.30

-We53 25 2 6 0.50 0. 1 8

Me 59 25 25 0.70 0.2 1 In summary, numerous benefits result from employing the concepts of the present invention. The combined magnetite particle and activated carbon composite of the present invention has been found to be very efficient in the adsorption of microbial contaminants from water and breathable air streams. The results are improvements on those obtained utilizing conventional granular carbon filters and monolithic carbon block filters not incorporating magnetite.

The unusual properties offered by the composite filters of the present invention offer potentially unique solutions to some of the problems in water treatment and remediation. The composite filter has a unique open internal structure that combined with a larger active surface for adsorption allows more efficient and rapid removal of contaminants than is attainable with conventional granular activated carbon beds. As a result, efficient adsoφtion can be achieved at short contact times and with low pressure energy requirements.

Additionally, results with a bacteria, E. coli, and a model virus, MS2, have shown the composites of the present invention incorporating magnetite particles removed the model viruses with a removal efficiency of greater than 5 logs. While the demonstrated virus removal is similar to that found by similar quantities of strictly carbon composite materials, the magnetite- carbon composite materials of the present invention had significantly improved adsorption and retention of bacteria. Further, the addition of magnetite to the composite filter improves the removal of metals from water and adds to the ease of material handling. The addition of magnetite to carbon composite materials also enhances electrical conductivity which can be used for heating of the filter units during regeneration and disinfection.

The foregoing description of preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. For example, it is apparent from the present invention that the concentration of magnetite could be varied within a single filter unit. Filters can be made to contain varying concentrations of magnetite at different depths within the filter by layering. A filter may start with 25% magnetite and finish with 0% magnetite, or other conceivable combinations. In this way, composite filters can be tailored to specific uses and do not have to be of a consistent magnetite percentage throughout the length of the filter.

The embodiment was chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled.

Claims

In the Claims

1. A composite filter for purifying a fluid stream, said filter comprising as an active agent an effective amount of adsorbent materials including a mixture of magnetite and activated carbon.

2. A composite filter for purifying a fluid stream, said filter comprising: an active agent including an effective amount of a mixture of magnetite and activated carbon; and a binder for binding said active agent together as a composite filter.

3. The composite filter of claim 2, wherein said magnetite is in the form of particles having a size of between substantially lμm - 1mm and the activated carbon is in the form of fibers having an average length of substantially 0.1-0.4mm and an average width of between substantially 5- 100 μm.

4. The composite filter of claim 3, wherein said activated carbon and said magnetite are provided in a weight ratio of between substantially 19:1 to 1 :1.

5. The composite filter of claim 4, wherein said activated carbon in said filter is subjected to a burnoff of between substantially 0-80% during activation.

6. The composite filter of claim 5, wherein said filter has a cured density of between substantially 0.2 - 0.75 g/cc and an activated density of between substantially 0.1 - 0.55 g/cc with a ratio of cured density to activated density of between substantially 1.8:1 to 1.1 :1.

7. The composite filter of claim 6, wherein said filter has a BET surface area of between substantially 300-2000 m²g.

8. The composite filter of claim 7, wherein said filter has a void volume of between substantially 63.2 - 94.7%.

9. A method ofpurifying a fluid stream, comprising: making a composite filter from a mixture of magnetite particles and activated carbon; passing a contaminated fluid stream through said filter; adsorbing and entrapping contaminants on surfaces of said

Fe₃0₄ particles and said activated carbon; and recovering a resulting decontaminated fluid stream.

10. The method of claim 9, including removing E. coli bacteria present in a drinking water fluid stream at a concentration of 1.4 X 10⁶ cfu/ml at a flow rate of at least 65 volumes of drinking water/volume of composite filter/hour for at least 9.5 minutes at a rate of at least 99.999%.

11. The method of claim 10 including making said composite filter into substantially any shape with a total volume of between 0.1-3000 cc.

12. A method for purifying a fluid stream, comprising: making a composite filter from a uniform mixture of about 25 weight percent magnetite particles and 75 weight percent activated carbon; and removing 99.999% of E.coli bacteria from water containing up to 1.3 X 10⁶ cfu/ml of E.coli for at least one hour at a flow rate of at least 8.78 volumes of water/volume of composite filter/hour.

13. The method of claim 12 including making said composite filter into substantially any shape with a total volume of between 0.1-3000 cc.