METHOD FOR REMOVING CONTAMINANT FROM A FLUID STREAM

Abstract

A method for removing at least one contaminant from a fluid stream by filtering the fluid stream with a filtration medium. The filtration medium includes an impregnate. The impregnate includes a surfactant such as sulfamic acid. The medium has from about 0.1 to about 25% by weight of impregnate. The method is useful for removing one or more volatile organic compounds, particularly formaldehyde, from the fluid stream. In some embodiments, the method includes removing at least two volatile organic compound contaminants from the fluid stream.

Claims

1. A method for removing a contaminant from a fluid stream comprising filtering the fluid stream with a filtration medium, wherein the filtration medium comprises an impregnate consisting of a surfactant.

2. The method of claim 1, wherein the contaminant comprises a volatile organic compound or combination of volatile organic compounds.

3. The method of claim 1, wherein the contaminant comprises formaldehyde.

4. The method of claim 1, wherein the method comprises removing at least two contaminants from the fluid stream.

5. The method of claim 4, wherein at least two of the contaminants are volatile organic compounds.

6. The method of claim 4, wherein at least one of the contaminants is formaldehyde.

7. The method of claim 1, wherein the medium comprises from about 0.1 to about 25% by weight of impregnate.

8. The method of claim 1, wherein the impregnate comprises from about 0.1 to about 10% by weight surfactant.

9. The method of claim 1, wherein the surfactant is sulfamic acid.

10. The method of claim 1, wherein the filtration medium further comprises a porous substrate.

11. The method of claim 10, wherein the porous substrate is selected from the group consisting of activated alumina, silica gel, zeolite, kaolin, adsorbent clay, activated bauxite, activated carbon and combinations thereof.

12. The method of claim 10, wherein the porous substrate is activated alumina, activated carbon, or a combination thereof.

13. The method of claim 10, wherein the porous substrate is activated alumina, zeolite or a combination thereof.

14. The method of claim 10, wherein the filtration medium is formed by applying the impregnate to the porous substrate.

15. The method of claim 14, wherein the impregnate is applied to the porous substrate in the form of a liquid solution.

16. The method of claim 10, wherein the impregnate is sprayed onto the porous substrate.

17. The method of claim 10, wherein the impregnate is applied to the porous substrate in the form of a powder.

18. The method of claim 10, wherein the impregnate is incorporated into the porous substrate prior to extrusion or pelletization of the substrate.

19. The method of claim 10, wherein the porous substrate is a woven or nonwoven material selected from the group consisting of glass fiber, crepe paper, kraft paper, wool, steel wool, silk, cellulosic fiber fabrics, synthetic fiber fabrics and combinations thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0020] Dry scrubbing air filtration media and methods of treating a fluid stream with the media are provided. The solid filtration media can be used to remove or reduce undesirable compounds, or contaminants, from a gaseous fluid stream. The solid filtration media contains an impregnate, which is a surfactant. The impregnate preferably, but does not have to be, applied to the air filtration media as a liquid impregnate solution.

[0021] Generally described, the filtration media contain a substrate impregnated with an impregnate that is composed of a solution containing a surfactant. A preferred surfactant is sulfamic acid. The filtration media include approximately 0.1 to about 25% by weight of the impregnate.

[0022] When applied to the filtration media, the surfactant allows the media to remove or reduce undesirable compounds, or contaminants, from a gaseous fluid stream. In particular, the filtration media can remove a volatile organic compound (VOC), or a combination of undesirable volatile organic compounds, particularly, but not limited to, formaldehyde. Previously known air filtration media have been unable to effectively and efficiently achieve this level of volatile organic compound filtration.

[0023] The surfactant component of the filtration media is believed to react with formaldehyde according to formula (I):

R—NH.sub.2+OCH.sub.2.fwdarw.R—N=CH.sub.2+H.sub.2O   (I)

[0024] The gaseous formaldehyde is thus converted to a solid organic nitrogen compound.

[0025] The surfactant also neutralizes the formaldehyde by catalyzing the breakdown of formaldehyde into water and carbon dioxide. The surfactant is not consumed in the catalytic reaction and is available to treat additional undesirable compounds.

[0026] The porous substrate to which the impregnate solution is applied may be selected from the group consisting of, but not limited to, activated alumina (Al.sub.2O.sub.3) (UOP Chemical, Baton Rouge, La.), silica gels (J. M. Huber, Chemical Division, Havre De Grace, Md.), zeolites (Steel Head Specialty Minerals, Spokane, Wash.), kaolin (Englehard Corp., Edison, N.J.), adsorbent clays (Englehard Corp., Edison, N.J.), activated bauxite, activated carbon such as activated carbon cloth, woven or non-woven particulate filters or combinations thereof. Preferably, the concentration of impregnate in the filtration media is about 0.1 to about 25% by weight.

[0027] Preferred porous substrates include alumina, activated carbon, and combinations thereof. Another preferred porous substrate is a combination of alumina and a zeolite. Though not intending to be bound by this statement, it is believed that zeolites further control the moisture content of the filtration media by attracting and holding water, which functions to keep more of the impregnate in solution. This effect, in turn, is believed to improve the capacity and efficiency of the filtration media. As used herein, the term zeolite includes natural silicate zeolites, synthetic materials and phosphate minerals that have a zeolite-like structure. Examples of zeolites that can be used in this media include, but are not limited to, amicite (hydrated potassium sodium aluminum silicate), analcime (hydrated sodium aluminum silicate), pollucite (hydrated cesium sodium aluminum silicate), boggsite (hydrated calcium sodium aluminum silicate), chabazite (hydrated calcium aluminum silicate), edingtonite (hydrated barium calcium aluminum silicate), faujasite (hydrated sodium calcium magnesium aluminum silicate), ferrierite (hydrated sodium potassium magnesium calcium aluminum silicate), gobbinsite (hydrated sodium potassium calcium aluminum silicate), harmotome (hydrated barium potassium aluminum silicate), phillipsite (hydrated potassium sodium calcium aluminum silicate), clinoptilolite (hydrated sodium potassium calcium aluminum silicate), mordenite (hydrated sodium potassium calcium aluminum silicate), mesolite (hydrated sodium calcium aluminum silicate), natrolite (hydrated sodium aluminum silicate), amicite (hydrated potassium sodium aluminum silicate), garronite (hydrated calcium aluminum silicate), perlialite (hydrated potassium sodium calcium strontium aluminum silicate), barrerite (hydrated sodium potassium calcium aluminum silicate), stilbite (hydrated sodium calcium aluminum silicate), thomsonite (hydrated sodium calcium aluminum silicate), and the like. Zeolites have many related phosphate and silicate minerals with cage-like framework structures or with similar properties as zeolites, which may also be used in place of, or along with, zeolites. These zeolite-like minerals include minerals such as kehoeite, pahasapaite, tiptopite, hsianghualite, lovdarite, viseite, partheite, prehnite, roggianite, apophyllite, gyrolite, maricopaite, okenite, tacharanite, tobermorite, and the like.

[0028] Terms such as “filtration media”, “adsorbent composition,” “chemisorbent composition,” and “impregnated substrate” are all interchangeable, and denote a substance that is capable of reducing or eliminating the presence of unwanted contaminants in fluid streams by the contact of such a substance with the fluid stream. It is to be understood that the term “fluid” is defined as a liquid or gas capable of flowing, or moving in a particular direction, and includes gaseous, aqueous, organic containing, and inorganic containing fluids.

[0029] The porous substrate can also be a woven or nonwoven material such as glass fiber, crepe paper, Kraft paper, wool, steel wool, silk, cellulosic fiber fabrics, synthetic fiber fabrics or combinations thereof. Preferred cellulosic fiber fabrics include cotton, linen, viscose and rayon. Preferred synthetic fiber fabrics include nylon, rayon, polyester, polyethylene, polypropylene, polyvinyl alcohol, acrylics, acetates, polyamide and carbon fiber.

[0030] As discussed above, the impregnate could be, but does not have to be, applied to the filtration media as a liquid impregnate solution. The liquid solution could be sprayed onto the filtration media or could be applied by other known methods.

[0031] Alternatively, the impregnate could be provided as a powder. The powder could be applied directly to the filtration media, or water or another liquid could be added to the powder to hydrate it prior to application of the impregnate composition onto the filtration media.

[0032] In addition, for extruded or pelletized filtration media (such as activated alumina or activated carbon-based media), the powder to could be added directly to the alumina/carbon/etc. material prior to its extrusion or pelletization. The impregnate would thus be more or less evenly distributed throughout the media, in contrast to media which has had a liquid impregnate sprayed onto its outer surfaces.

[0033] Specific methods of applying liquid or powder impregnate compositions onto air filtration media are known and are not important to the invention described herein.

Contaminant Removal Methods

[0034] Also provided is a method of treating a contaminated fluid stream using the dry scrubbing filtration media described herein. This method involves contacting the contaminated fluid stream with the solid filtration composition provided herein. Typically, the undesired contaminants will be removed from air, especially from air admixed with effluent gas streams resulting from municipal waste treatment facilities, paper mills, petrochemical refining plants, morgues, hospitals, anatomy laboratories, hotel facilities, museums, archives, computer and data storage rooms, and other commercial and industrial facilities. The filtration media is particularly useful in residential applications to reduce fumes from VOCs, such as formaldehyde. A liquid or powder impregnate could be sold to a consumer for manual application to a filter by the consumer. Methods of treating gaseous or other fluid streams are well known in the art. Any method known in the art of treating fluid streams with the media described herein may be used.

[0035] Some exemplary embodiments of the present invention will now be illustrated in the following specific, non-limiting example.

EXAMPLE

[0036] Air filtration media containing the impregnate solutions described herein have been shown to be much more efficient at removing gaseous VOC contaminants, particularly formaldehyde.

[0037] The filtration media is a 4 mm activated carbon porous substrate impregnated with the surfactant, sulfamic acid. As compared against known sodium permanganate-based filtration media, for example, the filtration media described herein has shown the following improved filtration capabilities and works better that other filter mediums:

TABLE-US-00001 Breakthrough Breakthrough Time Capacity PRODUCTS TESTED minutes hours % by weight Surfactant Impregnate 1,388 23.13 4.45% on 4 mm Activated Carbon (AC) PURAFIL SP - 1/16″ 1,191 19.85 2.48% 200 Series 746 12.43 1.56% AC/4 + IA/4 358 5.97 1.22% PURAFIL AP - 1/16″ 270 4.50 0.57% HCOH media - alumina based 293 4.88 0.56% HCOH media - carbon based 121 2.02 0.30% Purafil SP media - activated alumina pellets impregnated with sodium permanganate 200 Series - activated carbon impregnated with manganese oxide AC/4 + IA4 - activated carbon impregnated with potassium carbonate Purafil AP - 1/16″ - activated alumina impregnated with potassium iodine HCOH media - alumina based, activated alumina no impregnate HCOH media - carbon based, activated carbon no impregnate

[0038] Test method: The filtration capacity of each media tested was determined according to the principles described in ASTM D6646-01, “Standard Test Method for Determination of the Accelerated Hydrogen Sulfide Breakthrough Capacity of Granular and Pelletized Activated Carbon.” This test method is directed at filtration of hydrogen sulfide, but in this example was adapted for formaldehyde. Test Method ASTM D6646 is as follows:

[0039] ASTM D6646 Standard Test Method for Determination of the Accelerated Hydrogen Sulfide Breakthrough Capacity of Granular and Pelletized Activated Carbon.

[0040] Scope: This test method is intended to evaluate the performance of virgin, newly impregnated or in-service, granular or pelletized activated carbon for the removal of hydrogen sulfide from an air stream, under the laboratory test conditions described herein. A humidified air stream containing 1% (by volume) hydrogen sulfide is passed through a carbon bed until 50 ppm breakthrough of H.sub.25 is observed. The H.sub.2S adsorption capacity of the carbon per unit volume at 99.5% removal efficiency (g H.sub.2S/cm.sup.3 carbon) is then calculated. This test is not necessarily applicable to non-carbon adsorptive materials.

[0041] It should be understood, of course, that the foregoing relates only to certain embodiments of the present invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention. All of the publications or patents mentioned herein are hereby incorporated by reference in their entireties.