Process and apparatus for treating a gas containing a contaminant

• US 8,252,087 B2
• Filed: 10/31/2007
• Issued: 08/28/2012
• Est. Priority Date: 10/31/2007
• Status: Expired due to Fees

• Current Assignee: Molycorp Minerals LLC (Oaktree Capital Management LP)
• Original Assignee: Molycorp Minerals LLC (Oaktree Capital Management LP)
• Inventors: Burba, John L. III, Oriard, Tim L.
• Primary Examiner(s): Lawrence, Jr., Frank
• Application Number:
  US11/932,090
• Publication Number:
  US 20090112043A1
• Time in Patent Office: 1,763 Days
• Field of Search: 951/16, 95127-147, 959/00, 951/48, 95/8, 95/11, 95/14, 95/19, 95/21, 423/230, 423/239.1, 423/240.S, 423/244.01, 423/245.1, 423/263, 588/299, 588/315, 588/320, 588/400, 588/402, 588/403, 588/405
• US Class Current: 95/8
• CPC Class Codes: A61L 2/04 Heat A61L2/08 takes precedence
• CPC Class Codes: A61L 2/085 Infrared radiation
• CPC Class Codes: A61L 2/20 Gaseous substances, e.g. vapours
• CPC Class Codes: A61L 9/16 using physical phenomena
• CPC Class Codes: B01D 2255/206 Rare earth metals
• CPC Class Codes: B01D 2258/0225 from chemical or biological warfare
• CPC Class Codes: B01D 53/44 Organic components

Abstract

Apparatus, process and article for treating a gas containing one or more of a chemical and/or biological contaminant. The process includes contacting the gas with an aggregate composition comprising an insoluble rare earth-containing compound to form a gas depleted of chemical and active biological contaminants. The insoluble rare earth-containing compound can include one or more of cerium, lanthanum, or praseodymium. The composition comprises no more than two elements selected from the group consisting of yttrium, scandium, and europium when the aggregate has been sintered. A suitable insoluble cerium-containing compound can be derived from cerium carbonate. In one embodiment, the aggregate composition consists essentially of one or more cerium oxides, and optionally, a binder. Although intended for a variety of fluid treatment applications, such applications specifically include the treatment of breathing gases such as air that may contain chemical and/or biological contaminants.

Claims

1. A process, comprising:

contacting a contaminated gas containing one or more of a chemical and an active biological contaminant with a cerium (IV) oxide-containing aggregate composition to remove the one or more of a chemical and active biological contaminant, respectively, to form a decontaminated gas and a contacted cerium (IV) oxide-containing aggregate composition, wherein the contacted cerium (IV) oxide-containing aggregate composition comprises the one or more of the chemical and biological contaminants and wherein the cerium (IV) oxide-containing aggregate composition comprises at least about 50% by weight cerium (IV) oxide;

separating the decontaminated gas from the contacted cerium (IV) oxide-containing aggregate composition; and

sterilizing the contacted cerium (IV) oxide-containing aggregate composition to remove the one or more of a chemical and biological contaminants.

2. The process of claim 1, wherein the sterilizing comprises exposing the contacted cerium (IV) oxide-containing aggregate composition to an elevated temperature, wherein the one or more of a chemical and an active biological contaminant is the active biological contaminant, and wherein the cerium (IV) oxide-containing aggregate composition kills the active biological contaminant.

3. The process of claim 1, wherein the sterilizing comprises exposing the contacted cerium (IV) oxide-containing aggregate composition to an elevated pressure, wherein the one or more of a chemical and an active biological contaminant is the active biological contaminant, and wherein the cerium (IV) oxide-containing aggregate composition kills the active biological contaminant.

4. The process of claim 1, wherein the sterilizing comprises exposing the contacted cerium (IV) oxide-containing aggregate composition to an elevated level of radiation, the radiation being ultraviolet, microwave, and/or ionizing radiation wherein one or more of a chemical and an active biological contaminant is the active biological contaminant, and wherein the cerium (IV) oxide-containing aggregate composition kills the active biological contaminant.

5. The process of claim 1, wherein the sterilizing comprises exposing the contacted cerium (IV) oxide-containing aggregate composition to a chemical oxidant, and wherein, the one or more of a chemical and an active biological contaminant is the chemical contaminant.

6. The process of claim 1, wherein the sterilizing comprises exposing the contacted cerium (IV) oxide-containing aggregate composition to a chemical reductant and wherein the one or more of a chemical and an active biological contaminant is the chemical contaminant.

7. The process of claim 1, wherein the sterilizing comprises exposing the contacted cerium (IV) oxide-containing aggregate composition to a chemical species comprising one or more of a halogen, reactive oxygen species, formaldehyde, a surfactant, a metal other than a rare earth, and a gas selected from the group consisting of ethylene oxide, methyl bromide, beta-propiolactone, propylene oxide, and mixtures thereof.

8. The process of claim 1, further comprising:

sensing a property of the decontaminated gas to determine when to replace, the cerium (IV) oxide-containing aggregate composition, the sensing comprising one or more of a presence of the one or more of a chemical and biological contaminant in the decontaminated gas, decontaminated gas flow rate, decontaminated gas temperature, and decontaminated gas pressure.

9. The process of claim 8, wherein sensing comprises at least one of tagging and detecting the one or more of a chemical and biological contaminant in the decontaminated gas.

10. The process of claim 8, wherein sensing comprises measuring at least one of the decontaminated gas flow rate, temperature;

and pressure.

11. The process of claim 8, wherein sensing is performed by a sampling and conducting array.

12. The process of claim 8, wherein sensing comprises sensing for the presence of fines in the decontaminated gas.

13. The process of claim 1, wherein the decontaminated gas is substantially depleted of the chemical and active biological contaminants, wherein the cerium (IV) oxide-containing aggregate composition further comprises one or more of cerium (III), lanthanum, neodymium, and praseodymium, and wherein the cerium (IV) oxide-containing aggregate composition comprises aggregated particulates having a mean aggregate size of at least about 25 microns.

44. The method of claim 1, wherein the one or more of a chemical and biological contaminant is the chemical contaminant.

45. The method of claim 1, wherein the one or more of a chemical and biological contaminant is the chemical contaminant and wherein the chemical contaminant is one or more of 1,1,3,3,3-pentafluoro-2-(trifluoromethyl)-1-propene, phosgene, acetone, acrolein, aldrin, dieldrin, 2,3-benzofuran, bis(2-chloroethyl)ether, bis(chloromethyl)ether, bromodichloromethane, bromoform, bromomethane, 2-butanone, butraldehyde, carbon tetrachloride, chlordane, chlordecone, mirex, chlorinated dibenzo-p-dioxins (CDDs), chlorobenzene, chlorodibenzofurans (CDFs), chloroethane, chloroform, chloromethane, DDT, DDE, DDD, DEHP, di(2-ethylhexyl)phthalate, dibromochloropropane, 1,2-dibromoethane, 1,4-dichlorobenzene, 1,1-dichloroethane, 1,2-dichloroethane, 1,1-dichloroethene, 1,2-dichloroethene, 1,2-dichloropropane, 1,3-dichloropropene, diethyl phthalate, di-n-butylphtalate, di-n-octylphthalate (DNOP), 1,4-dioxane, dioxins, endrin, ethylene oxide, formaldehyde, freon 113, heptachlor, heptachlor epoxide, hexachlorobenzene, hexachlorobutadiene, hexachlorocyclohexane, hexachlorocyclopentadiene, hexachloroethane, 2-hexanone, isophorone, methoxychlor, methyl ethyl ketone, methyl isobutyl ketone, methyl t-butyl ether, methylchloroform, methylene chloride, methyl methacrylate, methyl-tert-butyl ether, perchloroethylene, polybrominated biphenyls (PBBs), polychlorinated biphenyls (PCBs), phthalic anhydride, pyrethrins, pyrethroids, 1,1,2,2-tetrachloroethane, tetrachloroethylene, tetrachloride, trichlorobenzene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethylene (TCE), 1,2,3-trichloropropane, vinyl acetate, and vinyl chloride.

14. A method, comprising:

(a) contacting a gas comprising a contaminant with an aggregate composition comprising cerium (IV) oxide and a different rare earth having a different oxidation state than cerium (IV) to form a treated gas substantially depleted of the contaminant, wherein;

(b) the contaminant is at least one of;

(B1) one or more of o-alkyl phosphonofluoridates, o-alkyl phosphoramidocyanidates, o-alkyl, s-2-dialkyl aminoethyl alkylphosphonothiolates, alkylated or protonated salts thereof, 2-chloroethylchloromethylsulfide, bis(2-chloroethyl)sulfide, bis(2-chloroethylthio)methane, 1,2-bis(2-chloroethylthio)ethane, 1,3-bis(2-chloroethylthio)-n-propane, 1,4-bis(2-chloroethylthio)-n-butane, 1,5-bis(2-chloroethylthio)-n-pentane, bis(2-chloroethylthiomethyl)ether, bis(2-chloroethylthioethyl)ether, bis(2-chloroethyl)ethylamine, bis(2-chloroethyl)methylamine, saxitoxin, ricin, alkyl phosphonyldifluoride, alkyl phosphonites, chlorosarin, chlorosoman, amiton, 1,1,3,3,3-pentafluoro-2-(trifluoromethyl)-1-propene, 3-quinuclidinyl benzilate, methylphosphonyl dichloride, dimethyl methylphosphonate, dialkyl phosphoramidic dihalides, alkyl phosphoramidates, diphenyl hydroxyacetic acid, quinuclidin-3-ol, dialkyl aminoethyl-2-chlorides, dialkyl aminoethane-2-ols, dialkyl aminoethane-2-thiols, thiodiglycols, pinacolyl alcohols, phosgene, cyanogen chloride, hydrogen cyanide, chloropicrin, phosphorous oxychloride, phosphorous trichloride, phosphorus pentachloride, alkyl phosphorous oxychloride, alkyl phosphites, phosphorous trichloride, phosphorus pentachloride, alkyl phosphites, sulfur monochloride, sulfur dichloride, thionyl chloride, ethers, carbonyls, acetaldehyde, acetone, acrolein, acrylamide, acrylic acid, acrylonitrile, aldrin, dieldrin, ammonia, aniline, atrazine, benzidine, 2,3-benzofuran, beryllium, 1,1′

-biphenyl, bis(2-chloroethyl)ether, bis(chloromethyl)ether, bromodichloromethane, bromoform, bromomethane, 1,3-butadiene, 1-butanol, 2-butanone, 2-butoxyethanol, butraldehyde, carbon disulfide, carbon tetrachloride, carbonyl sulfide, chlordane, chlordecone, mirex, chlorfenvinphos, chlorinated dibenzo-p-dioxins (CDDs), chlorine, chlorobenzene, chlorodibenzofurans (CDFs), chloroethane, chloroform, chloromethane, chlorophenols, chlorpyrifos, creosote, cresols, cyclohexane, DDT, DDE, DDD, DEHP, di(2-ethylhexyl)phthalate, diazinon, dibromochloropropane, 1,2-dibromoethane, 1,4-dichlorobenzene, 3,3′

-dichlorobenzidine, 1,1-dichloroethane, 1,2-dichloroethane, 1,1-dichloroethene, 1,2-dichloroethene, 1,2-dichloropropane, 1,3-dichloropropene, dichlorvos, diethyl phthalate, diisopropyl methylphosphonate, di-n-butylphtalate, dimethoate, 1,3-dinitrobenzene, dinitrocresols, dinitrophenols, 2,4-dinitrotoluene, 2,6-dinitrotoluene, 1,2-diphenylhydrazine, di-n-octylphthalate (DNOP), 1,4-dioxane, dioxins, disulfoton, endosulfan, endrin, ethion, ethylbenzene, ethylene oxide, ethylene glycol, ethylparathion, fenthions, formaldehyde, freon 113, heptachlor, heptachlor epoxide, hexachlorobenzene, hexachlorobutadiene, hexachlorocyclohexane, hexachlorocyclopentadiene, hexachloroethane, hexamethylene diisocyanate, hexane, 2-hexanone, HMX (octogen), hydraulic fluids, hydrazines, hydrogen sulfide, iodine, isophorone, malathion, MBOCA, methamidophos, methanol, methoxychlor, 2-methoxyethanol, methyl ethyl ketone, methyl isobutyl ketone, methyl mercaptan, methylparathion, methyl t-butyl ether, methylchloroform, methylene chloride, methylenedianiline, methyl methacrylate, methyl-tert-butyl ether, mirex, chlordecone, monocrotophos, N-nitrosodimethylamine, N-nitrosodiphenylamine, N-nitrosodi-n-propylamine, naphthalene, nitrobenzene, nitrophenols, perchloroethylene, pentachlorophenol, phenol, phosphamidon, phosphorus, polybrominated biphenyls (PBBs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), propylene glycol, phthalic anhydride, pyrethrins, pyrethroids, pyridine, RDX (cyclonite), selenium, styrene, sulfur dioxide, sulfur trioxide, sulfuric acid, 1,1,2,2-tetrachloroethane, tetrachloroethylene, tetryl, thallium, tetrachloride, trichlorobenzene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethylene (TCE), 1,2,3-trichloropropane, 1,2,4-trimethylbenzene, 1,3,5-trinitrobenzene, 2,4,6-trinitrotoluene (TNT), vinyl acetate, and vinyl chloride; and

(B2) an active biological contaminant;

wherein;

the aggregate composition comprises a plurality of extruded aggregated particulates comprising cerium (IV) oxide-containing particles and a binder;

the aggregate composition comprises at least about 75% by weight cerium (IV)-oxide;

the extruded aggregated particulates have an average surface area of at least about 70 m²/g; and

the extruded aggregated particulates have a mean aggregate size of at least about 25 μ

m.

15. The method of claim 14, wherein the binder is one or more of a fluorosilicone, fluorocarbon resin, perfluoroelastomer, and fluoroelastomer.

16. The method of claim 14, wherein the extruded aggregated particulates do not comprise a substrate and have a mean aggregate size of at least about 0.1 mm and wherein the mean particle size of the plurality of cerium (IV) oxide-containing particles is at least about 1 μ

m.

17. The method of claim 14, wherein the aggregate composition comprises at least about 95% by weight cerium oxide.

18. The method of claim 14, wherein the extruded aggregated particulates have an average surface area of at least about 85 m²/g.

19. The method of claim 14, wherein the aggregate composition further comprises:

a decontamination agent selected from the group consisting of transition metals, alkaline metals, polyoxometallates, quaternary ammonium complexes, zeolites, enzymes, and derivatives and mixtures thereof.

20. The method of claim 14, wherein the binder comprises one or more polymers selected from the group consisting of thermosetting polymers, thermoplastic polymers, elastomeric polymers, cellulosic polymers, glasses, and mixtures thereof and wherein the aggregate composition is adhered to or embedded in an outer surface of a filter substrate.

21. The method of claim 14, wherein the binder has a melting point between about 50 to about 500°

C.

22. The method of claim 14, wherein the binder is biodegradable.

23. The method of claim 14, wherein the binder is one of a mineral and clay.

24. The method of claim 14, wherein the contaminant comprises at least one member of B1.

25. The method of claim 14, wherein the contaminant comprises B2.

26. The method of claim 14, wherein the aggregate composition comprises no more than two elements selected from the group consisting of yttrium, scandium, and europium when the aggregate composition has been sintered.

27. The method of claim 14, further comprising a flow aid selected from the group consisting of ferric sulfates, ferric chlorides, ferrous sulfates, aluminum sulfates, sodium aluminates, polyaluminum chlorides, aluminum trichlorides, silicas, diatomaceous earths, organic flocculents, and mixtures, thereof.

28. The method of claim 14, further comprising an ion-exchange material.

42. The method of claim 25, wherein the active biological contaminant is one or more of Entamoeba histolytica, Giardia, and Cryptosporidium parvum.

43. The method of claim 25, wherein the active biological contaminant is algae.

29. A method, comprising:

contacting a cerium (IV) oxide-containing compound with a gas to remove, from the gas, a contaminant that is one or more of 1,1,3,3,3-pentafluoro-2-(trifluoromethyl)-1-propene, phosgene, acetone, acrolein, aldrin, dieldrin, 2,3-benzofuran, bis(2-chloroethyl)ether, bis(chloromethyl)ether, bromodichloromethane, bromoform, bromomethane, 2-butanone, butraldehyde, carbon tetrachloride, chlordane, chlordecone, mirex, chlorinated dibenzo-p-dioxins (CDDs), chlorobenzene, chlorodibenzofurans (CDFs), chloroethane, chloroform, chloromethane, DDT, DDE, DDD, DEHP, di(2-ethylhexyl)phthalate, dibromochloropropane, 1,2-dibromoethane, 1,4-dichlorobenzene, 1,1-dichloroethane, 1,2-dichloroethane, 1,1-dichloroethene, 1,2-dichloroethene, 1,2-dichloropropane, 1,3-dichloropropene, diethyl phthalate, di-n-butylphtalate, di-n-octylphthalate (DNOP), 1,4-dioxane, dioxins, endrin, ethylene oxide, formaldehyde, freon 113, heptachlor, heptachlor epoxide, hexachlorobenzene, hexachlorobutadiene, hexachlorocyclohexane, hexachlorocyclopentadiene, hexachloroethane, 2-hexanone, isophorone, methoxychlor, methyl ethyl ketone, methyl isobutyl ketone, methyl t-butyl ether, methylchloroform, methylene chloride, methyl methacrylate, methyl-tert-butyl ether, perchloroethylene, polybrominated biphenyls (PBBs), polychlorinated biphenyls (PCBs), phthalic anhydride, pyrethrins, pyrethroids, 1,1,2,2-tetrachloroethane, tetrachloroethylene, tetrachloride, trichlorobenzene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethylene (TCE), 1,2,3-trichloropropane, vinyl acetate, and vinyl chloride to yield a treated gas substantially depleted of the contaminant.

30. The method of claim 29, wherein the cerium (IV) oxide-containing compound comprises at least one other rare earth selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and mixtures thereof and wherein the cerium (IV) and at least one other rare earth have different oxidation states.

31. The method of claim 29, wherein cerium (IV) oxide-containing compound comprises at least one other rare earth selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and mixtures thereof and wherein the cerium (IV) and at least one other rare earth have different valence states.

32. The method of claim 30, wherein the contaminant has an electro-negative functional group that is reactive with the cerium (IV) oxide-containing compound, and wherein the electro-negative functional group comprises at least one of chloride, fluoride, bromide, ether, and carbonyl.

33. The method of claim 31, wherein the cerium (IV) oxide-containing compound is in an aggregate composition comprising at least about 75% by weight cerium (IV) oxide.

34. A method, comprising:

(a) receiving a gas comprising a contaminant that comprises at least one of;

(A1) one or more of o-alkyl phosphonofluoridates, o-alkyl phosphoramidocyanidates, o-alkyl, s-2-dialkyl aminoethyl alkylphosphonothiolates, alkylated or protonated salts thereof, 2-chloroethylchloromethylsulfide, bis(2-chloroethyl)sulfide, bis(2-chloroethylthio)methane, 1,2-bis(2-chloroethylthio)ethane, 1,3-bis(2-chloroethylthio)-n-propane, 1,4-bis(2-chloroethylthio)-n-butane, 1,5-bis(2-chloroethylthio)-n-pentane, bis(2-chloroethylthiomethyl)ether, bis(2-chloroethylthioethyl)ether, bis(2-chloroethyl)ethylamine, bis(2-chloroethyl)methylamine, saxitoxin, ricin, alkyl phosphonyldifluoride, alkyl phosphonites, chlorosarin, chlorosoman, amiton, 1,1,3,3,3-pentafluoro-2-(trifluoromethyl)-1-propene, 3-quinuclidinyl benzilate, methylphosphonyl dichloride, dimethyl methylphosphonate, dialkyl phosphoramidic dihalides, alkyl phosphoramidates, diphenyl hydroxyacetic acid, quinuclidin-3-ol, dialkyl aminoethyl-2-chlorides, dialkyl aminoethane-2-ols, dialkyl aminoethane-2-thiols, thiodiglycols, pinacolyl alcohols, phosgene, cyanogen chloride, hydrogen cyanide, chloropicrin, phosphorous oxychloride, phosphorous trichloride, phosphorus pentachloride, alkyl phosphorous oxychloride, alkyl phosphites, phosphorous trichloride, phosphorus pentachloride, alkyl phosphites, sulfur monochloride, sulfur dichloride, thionyl chloride, ethers, carbonyls, acetaldehyde, acetone, acrolein, acrylamide, acrylic acid, acrylonitrile, aldrin, dieldrin, ammonia, aniline, atrazine, benzidine, 2,3-benzofuran, beryllium, 1,1′

-biphenyl, bis(2-chloroethyl)ether, bis(chloromethyl)ether, bromodichloromethane, bromoform, bromomethane, 1,3-butadiene, 1-butanol, 2-butanone, 2-butoxyethanol, butraldehyde, carbon disulfide, carbon tetrachloride, carbonyl sulfide, chlordane, chlordecone, mirex, chlorfenvinphos, chlorinated dibenzo-p-dioxins (CDDs), chlorine, chlorobenzene, chlorodibenzofurans (CDFs), chloroethane, chloroform, chloromethane, chlorophenols, chlorpyrifos, creosote, cresols, cyclohexane, DDT, DDE, DDD, DEHP, di(2-ethylhexyl)phthalate, diazinon, dibromochloropropane, 1,2-dibromoethane, 1,4-dichlorobenzene, 3,3′

-dichlorobenzidine, 1,1-dichloroethane, 1,2-dichloroethane, 1,1-dichloroethene, 1,2-dichloroethene, 1,2-dichloropropane, 1,3-dichloropropene, dichlorvos, diethyl phthalate, diisopropyl methylphosphonate, di-n-butylphtalate, dimethoate, 1,3-dinitrobenzene, dinitrocresols, dinitrophenols, 2,4-dinitrotoluene, 2,6-dinitrotoluene, 1,2-diphenylhydrazine, di-n-octylphthalate (DNOP), 1,4-dioxane, dioxins, disulfoton, endosulfan, endrin, ethion, ethylbenzene, ethylene oxide, ethylene glycol, ethylparathion, fenthions, formaldehyde, freon 113, heptachlor, heptachlor epoxide, hexachlorobenzene, hexachlorobutadiene, hexachlorocyclohexane, hexachlorocyclopentadiene, hexachloroethane, hexamethylene diisocyanate, hexane, 2-hexanone, HMX (octogen), hydraulic fluids, hydrazines, hydrogen sulfide, iodine, isophorone, malathion, MBOCA, methamidophos, methanol, methoxychlor, 2-methoxyethanol, methyl ethyl ketone, methyl isobutyl ketone, methyl mercaptan, methylparathion, methyl t-butyl ether, methylchloroform, methylene chloride, methylenedianiline, methyl methacrylate, methyl-tert-butyl ether, mirex, chlordecone, monocrotophos, N-nitrosodimethylamine, N-nitrosodiphenylamine, N-nitrosodi-n-propylamine, naphthalene, nitrobenzene, nitrophenols, perchloroethylene, pentachlorophenol, phenol, phosphamidon, phosphorus, polybrominated biphenyls (PBBs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), propylene glycol, phthalic anhydride, pyrethrins, pyrethroids, pyridine, RDX (cyclonite), selenium, styrene, sulfur dioxide, sulfur trioxide, sulfuric acid, 1,1,2,2-tetrachloroethane, tetrachloroethylene, tetryl, thallium, tetrachloride, trichlorobenzene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethylene (TCE), 1,2,3-trichloropropane, 1,2,4-trimethylbenzene, 1,3,5-trinitrobenzene, 2,4,6-trinitrotoluene (TNT), vinyl acetate, and vinyl chloride; and

(A2) an active biological contaminant; and

(b) contacting the gas with aggregated particulates comprising cerium (IV) oxide and at least one other rare earth selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and mixtures thereof to remove the contaminant and provide a gas substantially depleted of the contaminant, wherein the at least one other rare earth has at least one of an oxidation state and valence state different from cerium (IV).

35. The method of claim 34, wherein the contaminant is a member of (A1) and wherein the aggregated particulates comprise at least about 75% by weight cerium (IV) oxide.

36. The method of claim 34, wherein the contaminant is a member of (A2) and wherein the aggregated particulates comprise at least about 75% by weight cerium (IV) oxide.

37. The method of claim 35, wherein each of the cerium (IV) oxide and the other rare earth remove contaminant (A1).

38. The method of claim 36, wherein each of the cerium (IV) oxide and the other rare earth remove the active biological contaminant.

39. The method of claim 34, wherein the cerium (IV) and at least one other rare earth have different oxidation states, wherein the aggregated particulates comprise rare earth-containing particles and a binder, wherein the rare earth-containing particles have a mean particle size of at least about 1 μ

m, and wherein the rare earth-containing particles comprise cerium (IV) oxide and lanthanum (III).

40. The method of claim 34, wherein the cerium (IV) oxide and the other rare earth comprise mixed valence states, wherein the aggregated particulates comprise rare earth-containing particles and a binder, wherein the rare earth-containing particles have a mean particle size of at least about 1 μ

m, and wherein the rare earth-containing particles comprise cerium (IV) oxide and lanthanum (III).

41. The method of claim 36, wherein the active biological contaminant comprises one or more of bacteria, fungi, protozoa, viruses, and algae.

46. The method of claim 34, wherein the contaminant comprises one or more of bacteria, fungi, protozoa, viruses, and algae, wherein the aggregated particulates comprises cerium (IV) oxide and a lanthanum compound, and wherein the lanthanum compound has a different activity and effect compared to the cerium (IV) oxide.