Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/70—Treatment of water, waste water, or sewage by reduction
  • C02F1/705—Reduction by metals
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2303/00—Specific treatment goals
  • C02F2303/18—Removal of treatment agents after treatment
  • C02F2303/185—The treatment agent being halogen or a halogenated compound

Definitions

• Chloramine is commonly used in low concentration as a secondary disinfectant in municipal water distribution systems as an alternative to chlorination with free chlorine. Concerns over taste and odor of chloramine treated water have led to an increase in the demand for water filters with chloramine removal capabilities.
• Carbon particles such as activated carbon particles, have been used to remove chloramine from aqueous streams. Improvements in removal of chloramine can be achieved by reducing the mean particle diameter of the carbon and by increasing the carbon bed contact time. Although parameters such as contact time and mean particle diameter are known to affect chloramine removal efficiencies, more significant improvements are desired without significantly increasing the pressure drop of filtration media.
• U.S. Pat. No. 5,338,458 (Carrubba et al.) discloses an improved process for the removal of chloramine from gas or liquid media by contacting the media with a catalytically-active carbonaceous char.
• U.S. Pat. No. 6,699,393 shows improved chloramine removal from fluid streams, when the fluid stream is contacted with an activated carbon, which has been pyrolyzed in the presence of nitrogen-containing molecules, versus a catalytically-active carbonaceous char.
• WO 201 1/125504 discloses an activated carbon containing 1.40-4.30 mass % oxygen, 0.90-2.30 mass % nitrogen, 0.05-1.20 mass % sulfur, and 0.40-0.65 mass % hydrogen, which is said to effectively break down chloramines.
• a method for removing chloramine from aqueous solutions comprising: providing an aqueous solution comprising chloramine and contacting the aqueous solution with a solid, wherein the surface of the solid comprises a metal or metal-containing compound, and wherein the metal is selected from the group consisting of palladium and platinum.
• the solid comprises a support having a surface, wherein the surface comprises the metal or metal-containing compound.
• a metal-containing particulate is mixed with a support particulate, wherein the D 50 of the metal-containing particulate is at least 5 times smaller than the D 50 of the support particulate.
• Fig. 1 is a chart of the percent chloramine reduction versus time for Substrate B and Examples 1-4.
• Fig. 2 is a chart of the percent chloramine reduction versus time for Substrate B and Examples 5-6.
• Fig. 3 is a chart of the percent chloramine reduction versus time for Substrate B, and Example 7.
• Fig. 4 is a chart of the percent chloramine reduction versus time for Substrate B, Comparative Example A, and Example 8.
• Fig. 5 is a chart of the percent chloramine reduction versus time for Substrate B and Examples 9-12
• Fig. 6 is a chart of the percent chloramine reduction versus time for Substrate B, Comparative Examples B-C, and Example 13. DETAILED DESCRIPTION
• Dj o refers to the particle size for which only 10 percent by volume of the particles in a particle distribution are smaller
• D50 refers to the particle size for which 50 percent by volume of the particles in a particle distribution are smaller (also commonly referred to in the art as the average or mean particle size);
• D90 refers to that particle size for which 90 percent by volume of the particles in a particle distribution are smaller
• a and/or B includes, (A and B) and (A or B).
• At least one includes all numbers of one and greater (e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.).
• the present disclosure is directed to a filtration medium comprising a solid wherein the solid comprises platinum, palladium, and combinations thereof (herein referred to as noble metals), or compounds containing these particular noble metals. Filtration media comprising these noble metals may be used for the removal of chloramine from aqueous solutions.
• a solid comprising the noble metal may be contacted with an aqueous solution comprising the chloramine.
• Such solids may include for example, platinum solid, platinum oxide, platinum hydroxide, platinum hydride, palladium solid, palladium oxide, palladium hydroxide, palladium hydride, and combinations thereof.
• platinum and palladium react with chloramine in a catalytic fashion.
• the chemical reaction with chloramine occurs predominately and/or exclusively on the surface of the media. Therefore, small quantities of these noble metals may be utilized.
• One aspect of the present disclosure is to provide supports comprising these noble metals.
• the noble metal (or compound comprising the noble metal) is added to the surface of the support (or substrate) to form, what is being referred to herein as the activated support.
• the supports of the present disclosure include both carbon-based and inorganic supports.
• the carbon-based support may be a granular material, a powder material, a fiber, a tube, a web, or a foam.
• the morphology of the carbon-based support is not particularly limited and may include a non-particulate, a particulate, or an aggregate. Additional exemplary morphologies include: a carbon block, a carbon monolith, foams, films, fibers, nanoparticulates, such as nanotubes and nanospheres.
• a non-particulate carbon-based support is a support that is not composed of discernable, distinct particles.
• a particulate carbon-based support is a support that has discernable particles, wherein the particle may be spherical or irregular in shape and has an average diameter of at least 0.1, 1, 5, 10, 20, or even 40 micrometers ( ⁇ ) to at most 75 ⁇ , 100 ⁇ , 500 ⁇ , 1 millimeter (mm), 2 mm, 4mm, 6.5 mm, or even 7 mm.
• An aggregate (or a composite) is formed by the joining or conglomeration of smaller particles with one another or with larger carrier particles or surfaces. The aggregates may be free standing (self-supporting against gravity). [0027] Typically, the morphology of the carbon-based support will be selected based on the application.
• particulate with a large particle size is desirable when the supports of the present disclosure are used in applications requiring low pressure drops such as in beds through which gases or liquids are passed.
• particle sizes of 20 to 200 ⁇ may be preferable when used in a carbon block monolith.
• the carbon-based support is comprised of activated carbon, in other words carbon that has been processed to make it highly porous (i.e., having a large number of pores per unit volume), which thus, imparts a high surface area.
• Carbon-based supports include: granular activated carbon available under the trade designation "RGC” by Mead Westvaco Corp, Richmond, VA may be preferred in water treatment. Activated coconut carbon available under the trade designation "KURARAY PGW” by Kuraray Chemical Co., LTD, Okayama, Japan may also be used.
• the morphology of the inorganic support is not particularly limited and may include a non-particulate, a particulate, or an aggregate.
• Exemplary morphologies include: fibers and nanoparticules such as nanotubes and nanospheres.
• the inorganic support may comprise, for example, silicon dioxide (silica), zirconia, titania, ceria, alumina, iron oxide, zinc oxide, tin oxide, alumina/silica, zirconia-silica, clays, talc- containing materials, spinel-structured oxides such as magnesium aluminate or cobalt iron oxide or the like, and other binary or ternary oxides of aluminum or silicon with other metal oxide materials.
• the inorganic support may be essentially pure, it may contain small amounts of stabilizing ion such as ammonium and alkaline metal ions, or it may be a combination of oxides such as a combination of titania and zirconia.
• support materials can include without limitation calcium carbonate, alumina, silica, zeolites, ion exchange resins and porous organic materials, activated carbon, metal oxides and metal oxide framework (MOF) materials, and inorganic oxides. All of these materials can be used in combination with one another or in combination with a carbon- based support.
• the size of the pores of the support can be selected based on the application.
• the support may be microporous, macroporous, mesoporous, or a mixture thereof.
• the support it is preferable for the support to be porous.
• the porous nature will enable, for example, more surface area for chloramine removal.
• Particularly useful are supports that have high surface area (e.g., at least 100, 500, 600 or even 700 m 2 /g; and at most 1000, 1200, 1400, 1500, 1800, or even 2000 m 2 /g based on BET (Brunauer Emmet Teller method) nitrogen adsorption).
• the solid comprises more than 0.1, 0.2, 0.5, 1, 1.5, 2, 2.5, 4, 5, 10, 15, or even 20% by mass of the noble metal. Larger values may be envisioned, however due to cost and the presumption of catalytic activity with chloramine, values less than 50%, 40%, 30%, or even 25% by mass of the noble metal are preferred.
• the surface of the support comprises platinum and/or palladium (or a compound containing such metals).
• the platinum and/or palladium is adherent to the surface of the support.
• the activated support is gently stirred with water, there is no apparent separation of the noble metal from the activated support.
• the noble metal is advantageous for the noble metal to be adherent to the support to contain the noble metal, preventing loss of the noble metal from the filtration media e.g., during washing of the filtration media.
• the platinum and palladium be located at the surface of the activated support to enable contact with the chloramine.
• the platinum and/or palladium (or a compound comprising the noble metal) may be applied to the surface of the support, using techniques known in the art. Such techniques include, for example, physical mixing, vacuum deposition, and wet impregnation.
• the activated support may be made by physical blending of the noble metal and the support involving mechanical and/or electrostatic mixing. Physical blending can be carried out by dry blending. "Dry blending" refers to blending the support particle and the noble metal in the absence of water and organic solvents. Dry blending can be carried out, for example, via convective mixing, diffusive mixing, and shear mixing mechanisms.
• contacting a support particle with the noble metal particulates can be carried out by tumbling the support particle and the noble metal (or compound comprising the noble metal) using conventional tumbling mixers (e.g., V-blender, double cone, or rotating cube); convective mixers (e.g., ribbon blender, nautamixer); fluidized bed mixers; or high-shear mixers.
• tumbling mixers e.g., V-blender, double cone, or rotating cube
• convective mixers e.g., ribbon blender, nautamixer
• fluidized bed mixers e.g., nautamixer
• the noble metal or a compound comprising the noble metal is mechanically mixed with the support to impinge the noble metal (or compound comprising the noble metal) onto the support.
• mechanical mixing includes for example, tumbling the components together with for example balls, magnetically-assisted impact coating, or exposing the support to a high velocity fluid comprising the noble metal (or compound comprising the noble metal).
• such mechanical mixing not only impinges the noble metal onto the surface of the support, but also decreases the particle size of the resulting activated support, thus creating metal-containing particulates.
• the metal-containing particulate may have a particle size of no more than 100, 50, 25, 20, 15, 10, 5 or even 1 micrometers.
• a noble metal-containing particulate is mixed with a support, which is a particulate, wherein the D 50 of the noble metal-containing particulate is at least 5, 10, 15, or even 20 times smaller than the D 50 of the support.
• the support is a highly porous substrate, such as an activated carbon, such a technique would provide and activated support that had a high loading of the noble metal-containing particulate.
• the activated support may be made by applying the noble metal, or a compound comprising the noble metal, to the surface of the support via a vacuum deposition method, including physical deposition and chemical deposition. Such techniques are known in the art.
• PVD Physical vapor deposition
• conductive layer can be carried out in various different ways. Representative approaches include sputter deposition, evaporation, laser ablation, and cathodic arc deposition. Any of these or other PVD approaches can be used in the process of the present disclosure, although the nature of the PVD technique can impact the resulting activity. For example, the energy of the PVD technique can impact the mobility of the deposited metal and hence its tendency to coalesce and form a continuous thin film.
• the activated support may be made by impregnating a support with the noble metal followed by reduction.
• a compound comprising the noble metal is mixed with solvent (e.g., water, or an organic solvent such as alcohol) to form a solution, which is used to impregnate the support.
• solvent e.g., water, or an organic solvent such as alcohol
• the impregnated support is reduced (e.g., using hydrogen) to generate the activated supports of the present disclosure.
• solvent e.g., water, or an organic solvent such as alcohol
• the surface of the support instead of comprising a uniform distribution of the noble metal, forms localized clusters (or aggregates) that are 1 nn or larger on the surface, or even 5 nm or larger on the surface.
• the platinum and palladium-containing compounds may be selected based on the technique used to treat the surface of the support.
• Exemplary platinum and palladium-containing compounds include for example, the corresponding metal hydrides, oxides, or hydroxides, chloroplatinic acid, palladium chloride, palladium nitrate, and combinations thereof.
• the platinum and palladium-containing compounds have a molecular weight less than 500 g/mol, 200 g/mol, or even less than 100 g/mol.
• the platinum and palladium-containing compounds do not substantially comprise a nitrogen-containing oxyanion, sulfur-containing anion, chloride, phosphate, or carboxylate.
• the noble metal-containing solid or activated support is disposed in a matrix.
• the matrix may be a web, a polymer-containing composite block, on the surface of a tube, or in another structure that enables aqueous solutions to pass therethrough.
• the filtration medium may be a compressed blend of the solid or activated support and a binder material, such as a polyethylene, e.g., an ultra high molecular weight polyethylene, or a high- density polyethylene (HDPE).
• the solid or activated support may be loaded into web, such as a blown microfiber, which may or may not be compacted such as described in U.S. Publ. No. 2009/0039028 (Eaton et al.), herein incorporated in its entirety.
• the loading expressed as weight of the solid or activated support by the total weight of the filtration media, can vary depending on matrix used.
• the amount of activated support (or the solid) comprises is at least 10, 25, 40, 50, 60, 75, or even 80 %; at most 90, 92, 95, 97, or 99%, or even 100% mass of the filtration media.
• the filtration media may comprise about 50-85% mass of the activated support (or the solid), while for a carbon loaded web, the filtration media may comprise about 80-95% mass of the activated support (or the solid).
• the solid or activated support is disposed in a fluid conduit, wherein the fluid conduit is fluidly connected to a fluid inlet and a fluid outlet.
• a fluid conduit is fluidly connected to a fluid inlet and a fluid outlet.
• Such systems may include packed beds.
• the solid or activated support may be used to remove chloramines from a fluid stream, particularly a liquid fluid stream, more specifically, an aqueous fluid stream.
• Chloramines are formed from the aqueous reaction between ammonia and chlorine (hypochlorite).
• NH 3 ammonia
• chloramine in low concentrations arise from the disinfection of potable water sources.
• the resulting aqueous solution comprises a reduced amount of chloramines.
• the chloramine content of water samples was determined from the total chlorine content in the samples.
• Total chlorine (OCl ⁇ and chloramines) concentration was measured by the DPD Total Chlorine Method, Hach Method 8167, which Hach Company claims to be equivalent to USEPA Method 330.5.
• the free chlorine (OC1-) concentration was periodically measured by the DPD Free Chloramine Analysis, Hach Method 8021, which Hach company claims is equivalent to EPA Method 330.5.
• Free chlorine was maintained at a negligible concentration ( ⁇ 0.2 ppm), thus, the total chlorine analysis was considered a good approximation of the concentration of chloramines in the water. All reagents and the instruments were those described in the standard Hach Method and can be obtained from Hach Company, Loveland, CO.
• 3 ppm choramine was prepared by adding the appropriate amount of commercial bleach (5.25% NaOCl) to deionized water. While stirring, 1.5 equivalents of a solution of ammonium chloride in water was added to the bleach solution and stirred for 1 hour. The pH was adjusted to 7.6 by the addition of NaOH or HC1 and tested using a pH meter (obtained from Thermo Fisher Scientific, Inc., Waltham, MA, under the trade designation "ORION 3-STAR").
• aqueous chloramine test solution comprising 3 ppm NH 2 C1 (prepared as described above) at a pH 7.6 at 27°C.
• the initial total chlorine content of the aqueous chloramine test solution was measured as described in the Chloramine Test above.
• a 0.46g aliquot of a carbon substrate sample i.e. a sample prepared according to Comparative Examples or the Examples according to the disclosure
• the samples were compared on a per volume basis, measuring 1.5 cc.
• a timer was started.
• Substrate A Activated carbon (80 x 325) was obtained from MeadWestvaco Specialty Chemicals, North Washington, SC, under the trade designation "RGC 325".
• Substrate B was an activated carbon powder with an ash content of 2.9 wt% (obtained under the trade designation "RGC POWDER", -325 mesh, from MeadWestvaco Specialty Chemicals, North Charleston, SC).
• a mixture of 0.04 g. platinum black (obtained from Aldrich Chemical Co., Milwaukee, WI) and 0.1 g of Substrate A was placed in a 10 x 25 mm stainless steel cylinder that contained two 6 mm stainless steel ball bearings and then milled for 1 min in a dental amalgamator (Wig-L- Bug, Crescent Dental Manufacturing Co., Elgin, IL). After milling, the finely powdered sample was intimately mixed by tumbling with 0.9 g of Substrate A. The Pt loading in the composite so produced was 4 wt %.
• Results are shown in Table 1, where for example, after 30 seconds of milling, 10% by volume of the particles are smaller than 2.2 ⁇ in diameter.
• Example 2 was prepared in the same manner as Example 1, except that 4 wt % PdO (obtained from Aldrich Chemical Co., Milwaukee, WI) was used in place of the platinum black.
• 4 wt % PdO obtained from Aldrich Chemical Co., Milwaukee, WI
• Example 3 was prepared in the same manner as Example 1, except that 0.5 wt % of Pd (obtained from Aldrich Chemical Co., Milwaukee, WI) was used instead of platinum black.
• Example 4 was prepared in the same manner as Example 1, except that 4 wt % of Pd was used instead of platinum black.
• the particle agitator shaft was rotated at about 6 rpm (revolutions per minute) during the palladium deposition process. The power was stopped after 2 hours. The chamber was backfilled with air and the palladium coated particles were removed and sieved through an 80 mesh screen.
• the palladium sputter target weight loss was 3.72 g. Based on the metal vapor capture efficiency of the agitator, the amount of palladium coated on the carbon particles was calculated to be approximately 1.8% by weight.
• Example 5 was analyzed by inductively coupled plasma mass spectrometry and found to have 1.5% wt palladium loading.
• Example 6 was prepared similarly to Example 5, except Substrate B was used in place of Substrate A.
• the palladium sputter target weight loss was 3.77g. Based on the metal vapor capture efficiency of the agitator, the amount of palladium coated on the carbon particles was calculated to be approximately 2.3 % by weight.
• Example 6 was analyzed by inductively coupled plasma mass spectrometry and found to have 2.2% wt palladium loading.
• Examples 5-6 and Substrate B (RGC POWDER) were tested for chloramine removal using the Chloramine Removal Test described above. The results are shown in Figure 2.
• Example 7 was a commercially available catalyst, 5% wt Pt on carbon (obtained from Engelhard Co., Iselin, NJ) and was used as received.
• Example 7 and Substrate B were tested for chloramine removal using the Chloramine Removal Test described above. The results are shown in Figure 3.
• Example 8 was a commercially available catalyst, 5% wt Pd on carbon (obtained from Engelhard Co., Iselin, NJ) and was used as received.
• Comparative Example A was a commercially available catalyst, 5 wt % rhodium on charcoal (Cat. No 8371 1, obtained from Aldrich Chemical Co., Milwaukee, WI) and was used as received.
• Example 9 was 5 wt % Pd on graphite (obtained from Johnson Matthey Co., Westchester, PA) and was used as received.
• Example 10 was 5 wt% Pd on CaC03 (obtained from Strem chemicals, Inc., Newburyport, MA) and was used as received.
• Example 1 1 was 5 wt % Pd/A1203 (Cat. No 205710, obtained from Aldrich Chemical Co., Milwaukee, WI) and was used as received.
• Example 12 was Pt02 (83.7 wt% Pt, obtained from Engelhard Co., Iselin, NJ) and was used as received.
• Examples 9-12 and Substrate B were tested for chloramine removal using the Chloramine Removal Test described above. The results are shown in Figure 5. Although the surface areas for Examples 9-12 were not measured, it is believed that the supports used in Examples 9-1 1 did not have a high surface area. [0099] Example 13
• Example 13 was 20 wt % palladium hydroxide on carbon (Pearlman's catalyst, Cat. No. 21291 1, obtained from Aldrich Chemical Co., Milwaukee, WI) and was used as received.
• Comparative Example B was 5 wt% ruthenium on carbon (Cat. No.206180, obtained from Aldrich Chemical Co., Milwaukee, WI) and was used as received.
• Comparative Example C was 5 wt % iridium on carbon (Cat. No.38330, obtained from Alfa-Aesar, Ward Hill, MA) and was used as received.
• Example 13 Comparative Examples B-C (Comp. Ex. B-C), and Substrate B (RGC POWDER) were tested for chloramine removal using the Chloramine Removal Test described above. The results are shown in Figure 6.

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Citations (5)

• 2013
  • 2013-06-10 WO PCT/US2013/044894 patent/WO2014042722A1/fr not_active Ceased

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