Air filtration media comprising metal-doped silicon-based gel and zeolite materials
An environmental control for use in air handling systems that provides highly effective filtration of noxious gases is provided. Such a filtration system utilizes a novel combination of at least one metal-doped silica-based gel and zeolite materials to trap and/or modify, and remove such undesirable gases (such as ammonia, ethylene oxide, formaldehyde, and nitrous oxide, as examples) from an enclosed environment. The gel component exhibits specific porosity requirements and density measurements; the zeolite component is generally acidic and is preferably not reacted with any salts or like substances. The novel combination of such gels and zeolites permits highly effective noxious gas filtration such that excellent breakthrough results are attained, particularly in comparison with prior media filtration products. Methods of using and specific filter apparatuses are also encompassed within this invention.
1 . A filter medium comprising a combination of at least two materials, one comprising a multivalent metal-doped silicon-based gel material, and the other comprising a zeolite material.
2 . The filter medium of claim 1 wherein said multivalent metal-doped silicon-based gel material exhibits a BET surface area of between than 100 and 300 m2/g; a pore volume of between about 0.18 cc/g to about 0.7 cc/g as measured by nitrogen porosimetry; a cumulative surface area measured for all pores having a size between 20 and 40 Å of between 50 and 150 m 2 /g; and wherein the multivalent metal doped on and within said silicon-based gel material is present in an amount of from 5 to 25% by weight of the total amount of the silicon-based gel material.
3 . The filter medium of claim 3 wherein said multivalent metal is selected from the group consisting of cobalt, iron, manganese, zinc, aluminum, chromium, copper, tin, antimony, tungsten, indium, silver, gold, platinum, mercury, palladium, cadmium, nickel, and any combinations thereof.
4 . The filter medium of claim 3 wherein said multivalent metal is copper.
5 . The filter medium of claim 1 wherein said zeolite material is a pentisil zeolite.
6 . The filter medium of claim 5 wherein said pentisil zeolite is ZSM-5.
7 . The filter medium of claim 2 wherein said zeolite material is a pentisil zeolite.
8 . The filter medium of claim 7 wherein said pentisil zeolite is ZSM-5.
9 . The filter medium of claim 3 wherein said zeolite material is a pentisil zeolite.
10 . The filter medium of claim 9 wherein said pentisil zeolite is ZSM-5.
11 . A filter system comprising the filter medium as defined in claim 1 .
12 . A filter system comprising the filter medium as defined in claim 2 .
13 . A filter system comprising the filter medium as defined in claim 3 .
14 . A filter system comprising the filter medium as defined in claim 4 .
15 . A filter system comprising the filter medium as defined in claim 5 .
16 . A filter system comprising the filter medium as defined in claim 6 .
17 . A filter system comprising the filter medium as defined in claim 7 .
18 . A filter system comprising the filter medium as defined in claim 8 .
19 . A filter system comprising the filter medium as defined in claim 9 .
20 . A filter system comprising the filter medium as defined in claim 10.