Surface-modified carbon and sorbents for improved efficiency in removal of gaseous contaminants
A material, and filters and other structures exposed to flowing gas that have the material therein, which removes VOCs, such as formaldehyde, from the gas. The material is a porous sorbent impregnated by a metal oxide, such as manganese oxide (MnOx) nano particles. The sorbent may be activated carbon, and the manganese oxide may catalyze formaldehyde to water and carbon dioxide while the carbon may adsorb formaldehyde, both mechanisms of which remove the VOC from the air to prevent or reduce inhalation of the same by humans. The material may be combined with an untreated sorbent or sorbent treated with ionic alkaline salts.
1. A method of forming a material for reacting with volatile organic compounds in a flow of gas, the method comprising:
(a) reacting at least one manganese precursor compound with a reducing agent of the at least one manganese precursor in aqueous phase to form metal oxide nanoparticles;
(b) depositing at least some of the metal oxide nanoparticles in a first porous sorbent having outer surfaces with pores extending internally to define passages, wherein the at least some of the metal oxide nanoparticles deposited in the first porous sorbent are disposed in at least some of the pores and some of the passages: and
(c) applying at least some of the metal oxide nanoparticles to a polymeric fibrous structure.
2. The method in accordance with claim 1 , wherein the step of depositing comprises combining the aqueous phase solution and the first porous sorbent and then drying the combination at a temperature lower than 150 degrees Celsius.
3. The method in accordance with claim 2 , wherein the step of depositing comprises spraying the aqueous phase solution on the first porous sorbent.
4. The method in accordance with claim 2 , wherein the step of depositing comprises soaking the first porous sorbent in the aqueous phase solution.
5. The method in accordance with claim 1 , wherein the step of reacting further comprises combining the manganese precursor compound with its reducing agent in aqueous phase and shaking the combination.
6. The method in accordance with claim 1 , wherein the step of reacting further comprises combining a manganese precursor with a reducing agent of the at least one manganese precursor in the range of about 0.5-5.0 weight percent of the first porous sorbent.
7. The method in accordance with claim 1 , whereby the precursor and the reducing agent are combined with the reducing agent maintained at a concentration that slows the reaction between the precursor and the reducing agent sufficiently to form nanoparticles within a size range of about 100 to about 400 nanometers.
8. The method in accordance with claim 1 , further comprising blending the first porous sorbent constituting about 40-50% by weight with a second porous sorbent constituting about 50-60% by weight, wherein the second porous sorbent is impregnated with ionic alkaline salts in at least pores formed on an outer surface of the second porous sorbent, after step (b).
9. The method in accordance with claim 1 , wherein the step of applying comprises coating the metal oxide nanoparticles on the polymeric fibrous structure.
10. The method in accordance with claim 1 , wherein the step of applying comprises retaining at least some of the first porous sorbent in a sheet of material that is interposed within the polymeric fibrous structure.
11. The method in accordance with claim 1 , wherein the step of applying comprises adhering at least some of the first porous sorbent to the polymeric fibrous structure.