EP1259323A2

EP1259323A2 - Fibers to immobilize ion exchange resins

Info

Publication number: EP1259323A2
Application number: EP01911217A
Authority: EP
Inventors: Peter D. Unger; Russell A. Dondero; Daniel Bause; Ronald P. Rohrbach; Lixin L. Xue; Gordon W. Jones
Original assignee: Honeywell International Inc
Current assignee: Honeywell International Inc
Priority date: 2000-03-03
Filing date: 2001-03-01
Publication date: 2002-11-27
Also published as: JP2003525739A; WO2001066249A2; WO2001066249A3

Abstract

A wicking fiber for use in immobolizing ion exchange resins is described. The filter medium includes at least one fiber having a liquid or solid material disposed on an external surface thereof. The fiber can include structures such as an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to the outer fiber formed between adjacent lobes. The material, which can be disposed within the internal cavity of the fiber, has a high affinity for dissolved or soluble material in order to strongly attract and retain the dissolved or soluble material, while at the same time not causing a substantial pressure drop across the filter medium.

Description

FIBERS TO IMMOBILIZE ION EXCHANGE RESINS

ΩΑCKCT.OTTND OF THE INVENTION

1. Technical Field

The present invention relates generally to the immobilization of ion exchange resins, and more particularly to wicking fibers having an ion exchange resin disposed on an exterior surface thereof for, among other things, selectively removing dissolved materials contained within a fluid.

2. Discussion Ion exchange is a process that removes detrimental ions (e.g., lead, copper, and so forth) from water and replaces them with less damaging ions . Ion exchange can most simply be described as the interchange of ions present in a liquid with those present on an insoluble solid with which the liquid comes into contact.

In practice, ion exchange occurs between water containing ions and an insoluble solid particle with ion exchange properties, and is practical only when the process is reversible. Typically, the insoluble solid ion exchange particle takes the form of a synthetic ion exchange resin bead. Typically, each resin bead is a porous polymer matrix containing many ion exchange sites both on the bead surface and within the matrix.

Ion exchange can only take place between ions of the same charge, namely anions for anions and cations for cations. Therefore, resins have to be charge specific, with some resins specifically designed for anion exchange, and others for cation exchange. Anion exchange resins have positively-charged exchange sites with anions attached, and cation exchange resins have negatively- charged exchange sites with cations attached.

Different ions have different affinities (ability to remain attached) to the ion exchange sites on resins. Using cation exchange resin as an example, in their regenerated state, all resin sites have a cation attached that has a certain affinity to the oppositely charged site. When water flows over and through the resin bead, cations which have a greater affinity to the exchange site will displace cations with lower affinities.

To ensure the maximum cation exchange ability, the resin sites are usually regenerated with low affinity cations, usually sodium or hydrogen ions. As virtually all other cations have a greater affinity for the exchange sites, the sodium or hydrogen ions are readily exchanged off the resin. The process for anion exchange is similar, except anion ^• resins are regenerated with chloride or hydroxyl ions.

Also, different ions can have different electric charges, which has an impact on the ion exchange at the molecular level. A monovalent ion has a single charge, divalent ions have two charges, trivalent ions have three charges, and so on. The net charge on a resin bead must remain neutral, so one divalent ion of greater affinity will displace two lower affinity monovalent ions. Conversely, two monovalent ions are required to displace one divalent ion. In typical water supplies, the ion exchange resin is more selective for divalent and trivalent ions than for monovalent ions. The regeneration of ion exchange resins is conventionally accomplished through the introduction of regenerating ions in concentrations much greater than those found in the untreated water. In a concentrated solution, the resin will be more selective for the monovalent ions . This overabundance of low affinity ions allows them to displace higher affinity ions by sheer kinetic brute force.

A description of ion exchange technology can be found in the following U.S. Patents: U.S. Patent No. 4,313,832 entitled g Method For

Treatment Of Aqueous Solutions With Ion Exchange Fibers^ and issued to Shimuza et al . ; U.S. Patent No. 4,661,327 entitled § Recovery Of Mineral Values Using Magnetically

Susceptible Ion Exchange AgentϊJ and issued to Horton; and U.S. Patent No. 5,405,509 entitled g Remediation Of A Bulk Source By Electropotential Ion Transport Using A Host Receptor Matrix^ and issued to Lomasney et al . , the entire specifications of which are all incorporated herein by reference . However, conventional devices and methods for immobilizing ion exchange resins, as well as removing dissolved materials contained within a fluid, have not been altogether satisfactory. This is especially true with respect to removing dissolved material (e.g., soluble ions) against a relatively high fluid flow with relatively minimal fluid restriction (e.g., pressure drop).

Therefore, there exists a need for an apparatus, and method of using the same, that is able to remove various types of dissolved materials from a fluid under relatively high flow rates and with relatively minimal fluid restriction.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a new and improved apparatus for removing a dissolved material from a fluid.

It is another object of the present invention to provide a new and improved apparatus for immobilizing an ion exchange resin.

It is still another object of the present invention to provide a new and improved apparatus for chelating an ionic species. It is yet still another object of the present invention to provide a new and improved method for removing a dissolved material from a fluid.

In accordance with one embodiment of the present invention, an apparatus for removing a dissolved material contained within a fluid is provided, comprising: at least one fiber; wherein the at least one fiber is comprised of an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to an outer fiber formed between adj acent lobes ; wherein the at least one fiber has at least one material disposed on an external surface thereof; wherein the at least one material has a high affinity for the dissolved material and is capable of removing the dissolved material from the fluid.

In accordance with another embodiment of the present invention, an apparatus for chelating an ionic species contained within a fluid is provided, comprising: at least one fiber; wherein the at least one fiber is comprised of an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to an outer fiber formed between adjacent lobes; wherein the at least one fiber has at least one material disposed on an external surface thereof; wherein the at least one material has a high affinity for the ionic species and is capable of chelating the ionic species .

In accordance with yet another embodiment of the present invention, a method for removing a dissolved material contained within a fluid is provided, comprising: providing at least one fiber, wherein the at least one fiber is comprised of an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to an outer fiber formed between adjacent lobes, wherein the at least one fiber has at least one material disposed on an external surface thereof, wherein the at least one material has a high affinity for the dissolved material; and passing the fluid through the at least one fiber; wherein the at least one material removes the dissolved material from the fluid.

A more complete appreciation of the present invention and its scope can be obtained from the following brief description of the drawings, detailed description of the invention, and the appended claims.

BRTEF DESCRIP IO OF THE DRAWINGS

FIG. 1 is a perspective view showing a wicking fiber which is suitable for practicing the invention; and FIG. 2 is a graphical illustration of the results of a copper breakthrough analysis.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is useful for removing dissolved material contained in a fluid material. Specifically, the present invention is based on the use of complex cross-section fibers to entrap and hold various materials, such as but not limited to ion exchange resins, and chromatographic materials such as, but not limited to metal affinity chromatography media, and the like.

In cases where it is highly desirable to immobilize chromatographic media against a high fluid flow with minimum flow restriction, the use of these complex cross-section fibers offers a convenient solution. One example of a situation where the overall efficiency is governed by exchange kinetics rather than by brute capacity is to be found in the area of reciprocating flow ion exchange ("recofo"). This process relies on rapid loading and stripping kinetics which implies very high flow rates . This process offers advantages in low capital, compact size due to low bed heights and minimum resin inventory and high efficiency.

A major limitation of the reciprocating flow ion exchange process is the requirement for the use of very fine resin particles to generate the rapid kinetics, thereby generating very high flow restrictions. Therefore, the impregnated wicking fibers of the present invention would appear to be highly suitable for application to this process.

The present invention employs a class of fibrous materials which have the ability to hold an impregnated material due to the nature of their unique cross-section. These fibers can be made into a variety of configurations, either of the woven or nonwoven varieties.

Examples of suitable fibers include, without limitation, elongated fibers having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to the outer fiber formed between adjacent lobes .

A description of several suitable fibers can be found in the following U.S. Patents, the entire specifications of which are all incorporated herein by reference:

U.S. Patent No. 5,057,368 entitled g Filaments Having Trilobal Or Quadrilobal Cross-Sections^ and issued to Largman et al . describes a trilobal or quadrilobal fiber formed from thermoplastic polymers, the fiber having a cross-section comprised of a central core having three or four T-shaped lobes, the legs of each intersecting at the center of the core such that the angle between the legs of adjacent lobes is from about 80° to about 130°. U.S. Patent No. 5,704,966 entitled g Method And

Apparatus For The Continuous Capturing And Removal Of Gas Molecules^ and issued to Rohrbach et al . describes a filtration method and device which continuously removes several gas phase contaminants from an air stream through the use of partially hollow wicking fibers impregnated with a selected liquid which can capture the gas phase contaminants .

U.S. Patent No. 5,713,971 entitled ξξ Filtration Device Using Absorption For The Removal Of Gas Phase Contaminantsϊ£ and issued to Rohrbach et al . describes a filter device and technique which rely on absorption rather than adsorption for the removal of gas phase contaminants. A filter media is composed of a plurality of wicking fibers each of which comprise a strand with a hollow region impregnated with any of a variety of liquid phase absorbing systems made from the combination of a carrier liquid and soluble complexing/degrading agent or agents. The filter media may be made from any of a variety of fibers which can rapidly transport a liquid phase by the nature of either their geometry or their chemical composition. Geometries may include multilobal cross-sectional configurations, porous hollow fibers, porous or striated fibers or tightly bundled microfibers, all of which exhibit the property of wicking fluid from an external source .

U.S. Patent Nos . 5,744,236 and 5,759,394 entitled § Hollow Fibers Impregnated With Solid Particles^ and ^■§ Elongate Fiber Filter Mechanically Securing Solid Absorbent Particles Between Adjacent Multilobesξξ , respectively, and both issued to Rohrbach et al . describe a non-woven filter media or mat formed from a plurality of elongated generally hollow fibers each having an internal cavity which has an opening, smaller than the cavity width, to the fiber surface and retaining within the internal cavity a large number of relatively small solid particles.

U.S. Patent Nos. 5,902,384 and 5,951,744 entitled i§ Wicking Fiber With Solid Particulates For A High Surface Area Odor Removing Filter And Method Of Making' and ^■§ Multicomponent Depth Odor Control Filter And Method Of Manufacture^ , respectively, and both issued to Rohrbach et al . describe a filtration device which continuously removes gas phase contaminants from an air stream through the use of partially hollow wicking fibers impregnated with a fine solid carbon powder or zeolites and formed into a fiber filter with a selected chemisoptive liquid applied to one side of the fiber filter and large carbon particles applied to the other side of the fiber filter.

The impregnated or pregnant fibers can either be formed into fibrous mats, sheets, or webs by any number of conventional methods, or alternatively, the pregnant fibers can be mechanically incorporated (e.g., disposed) onto and/or within a conventional fibrous mat, sheet, or web (typically comprised of a plurality of entangled non- woven fibers) .

Preferably, the resulting fibrous mat, whether comprised of, or incorporating, pregnant fibers is a low density, high pore volume material (e.g., 50% pore volume for fibers) . The high pore volume is preferred so as to allow the proper level of fluid flow through the fibrous mat without a significant pressure drop occurring.

Referring now to FIG. 1, a generally hollow fiber 10 which is suitable for practicing this invention is shown. The fiber 10 has a cross-section with a central core 12 and three (or alternatively four) T-shaped lobes 14 that terminate on an external wall member 16. The legs of the lobes 14 intersect at the core 12 so that the angle between the legs of the adjacent lobes 14 is from about 80° to 130°. The thermoplastic polymer is typically a polyamide, a polyester, a polyolefin or a combination thereof. The fiber 10 as illustrated in the FIGURE is formed as an extruded strand having three hollow interior longitudinally extending cavities 18 each of which communicates with the outer strand surface by way of longitudinally extending slots 20 which are defined between the outer ends of the T-shaped lobes 14. The extractant 22 for capturing dissolved material, for example, is applied in any number of conventional methods to at least a portion of one or more surfaces of the cavities 18. The extractant 22 can include ion exchange resins, immobilizing agents, chelating agents, and so forth. The wicking fibers of the present invention are capable of immobilizing an extractant within the microchannels (e.g., cavities) of the wicking fiber without the use of adhesives or binders. This entrapment is very strong, as mechanical vibration and air flow studies have indicated. It has been shown that carbon particles entrapped within the wicking fiber can withstand extremely high liquid flow rates exceeding 500 bed volumes per minute .

In accordance with one aspect of the present invention, an extractant or other like material, either in liquid or solid form is disposed on an external surface of the wicking fibers of the present invention, and more preferably in the cavities of the wicking fiber. By the term ^■ extractant^ as used herein, it is meant any material that is capable of removing another material contained in a fluid or solid. The extractant preferably captures, chelates, or immobilizes various materials, such as, but not limited to ionic species, and the like.

The following example is a non-limiting illustration of the use of liquid chelators (i.e., chelating agents) disposed on an external surface of the wicking fibers of the present invention in order to chelate metal ions contained within an aqueous solution:

EXAMPLE Wicking fiber, in accordance with one embodiment of the present invention, was impregnated with Moc-45, a selective ketoxime copper extractant. The fiber used in this example was in the form of a nonwoven fabric made from polypropylene polymer and has a weight basis of approximately 3 ounces per cubic yard. A sheet of this fabric (50 cm X 18 cm) was immersed in the Moc-45 liquid extractant in order to wet thoroughly. The excess liquid was removed from the fabric by compressing the wetted mat and allowing the excess fluid to drain away by gravity. The impregnated fiber mat was then allowed to air dry in a hood under airflow for a period of approximately 16-18 hours. The purpose of the drying step was to remove excess volatile kerosene carrier from the metal extractant mixture . The impregnated wicking fiber fabric was then laid over a polypropylene screen mesh support and rolled tightly into a tube or § Jellyroll§ . The tightly rolled tube was then inserted into a glass Kontes column (2.3 cm X 25 cm) , and the glass column was then fitted with inlet and outlet tubing connectors to allow introduction of a fluid process stream. The final weight of impregnated wicking fiber in the column was calculated to be 12.48 g. The wicking fiber bed occupied a space of 2.3 cm diameter by a bed height of 17 cm, yielding a volume of about 104 cubic cm. The column freeboard was approximately 33 cubic cm. The final calculated fabric loading was approximately 0.127 g of Moc-45 extractant per cubic cm of bed volume . Copper breakthrough analysis was performed by passing an aqueous solution of 2 g/1 copper sulfate over the. column packed with the Moc-45-impregnated wicking fiber, described above. The copper solution was pumped over the column at flow rates of 20 to 45 bed volumes/hour, and copper in the effluent stream was measured by UV absorbance at 254 nm. Results of one breakthrough analysis are shown in Figure 2. Following loading of the metal extractant with copper, the column was washed with water, and then the copper was stripped from the extractant using a solution of 1/8 M sulfuric acid in water. Following the acid stripping, the column was neutralized with water to prepare the extractant for another round of loading.

It should be noted that many types of materials, either liquid or solid, may be impregnated into the internal . cavities of the wicking fiber of the present invention. For example, any type of material that is used to selectively remove a dissolved material, such as an ionic species (e.g., anions and/or cations) from a fluid can be used, such as, but not limited to ion exchange resins, chelating agents, immobilizing agents, and the like.

The foregoing description is considered illustrative only of the principles of the invention. Furthermore, because numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and process shown as described above. Accordingly, all suitable modifications and equivalents that may be resorted to that fall within the scope of the invention as defined by the claims that follow.

Claims

What is claimed is:

1. An apparatus for removing a dissolved material contained within a fluid, comprising: at least one fiber; wherein the at least one fiber is comprised of an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to an outer fiber formed between adjacent lobes; wherein the at least one fiber has at least one material disposed on an external surface thereof; wherein the at least one material has a high affinity for the dissolved material and is capable of removing the dissolved material from the fluid.

2. The invention according to claim 1, wherein the lobes are T-shaped.

3. The invention according to claim 1, wherein the at least one material is disposed on at least a portion of a surface of the internal cavity.

4. The invention according to claim 1, wherein the at least one material is selected from the group consisting of immobilizing agents, chelating agents, and combinations thereof .

5. The invention according to claim 1, wherein the dissolved material is an ionic species.

6. An apparatus for chelating an ionic species contained within a fluid, comprising: at least one fiber; wherein the at least one fiber is comprised of an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to an outer fiber formed between adjacent lobes; wherein the at least one fiber has at least one material disposed on an external surface thereof; wherein the at least one material has a high affinity for the ionic species and is capable of chelating the ionic species .

7. The invention according to claim 6, wherein the lobes are T-shaped.

8. The invention according to claim 6, wherein the at least one material is disposed on at least a portion of a surface of the internal cavity.

9. The invention according to claim 7, wherein the ionic species is a metal ion.

10. A method for removing a dissolved material contained within a fluid, comprising: providing at least one fiber, wherein the at least one fiber is comprised of an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to an outer fiber formed between adjacent lobes, wherein the at least one fiber has at least one material disposed on an external surface thereof, wherein the at least one material has a high affinity for the dissolved material; and passing the fluid through the at least one fiber; wherein the at least one material removes the dissolved material from the fluid.

11. The invention according to claim 10, wherein the lobes are T-shaped.

12. The invention according to claim 10, wherein the at least one material is disposed on at least a portion of a surface of the internal cavity.

13. The invention according to claim 10, wherein the at least one material is selected from the group consisting of immobilizing agents, chelating agents, and combinations thereof .