Mesostructured Metal Oxide Nanocomposite Filter Medium for Air Purification

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Concern over the adverse short and long-term health effects associated with volatile organic compounds, sulfur dioxide and nitrogen oxides has created a need to develop better catalysts and filter medium to purify or filter air.  These compounds are released during combustion and energy production, reacting chemically in the atmosphere to create photochemical haze, acid rain and ground level ozone.  These harmful pollutants can cause adverse health and ecological effects, increasing the costs of healthcare, shortening life expectancy, and causing irreparable harm (relative to our lifetime) to our environment.

Ozone, even in low concentrations over short durations (hours), can cause reduced lung function and respiratory inflammation with symptoms like pulmonary congestion and chest pain in healthy individuals.  Long-term exposure can create irreversible structural damage to the lungs in healthy individuals.  The damage and resultant symptoms are much worse in those with impaired cardiopulmonary systems.  SO2 aggravates cardiopulmonary disorders and can cause respiratory illnesses.  NOx can aggravate respiratory disorders as well as reduce immune response to influenza and other illnesses.  Both SO2 and NOx can react in the atmosphere to form acid rain, and NOx can cause eutrophication in coastal waters.

Japanese Researchers have developed a mesoporous composite catalyst that can react with and degrade VOCs, SO2 and NOx[1]. The catalyst reacts with these compounds in both ambient and process air, reducing these pollutants to much less toxic substances like carbon dioxide and bulk pollutants.  The pollutants are converted to more stable compounds which are then trapped on the filter medium.  These more benign substances can be extracted later during the recharge of the filter medium[2]

Manganese oxide nanoparticles are used due to their extremely high surface area; greater than 300 square meters per gram.  Gold nanoparticles are then deposited on this oxide through vacuum ultraviolet laser ablation techniques, creating a material with an exceptional ability to catalyze VOCs, SO2 and NOx.  Cbining these particles into mesoporous filter medium has been shown to reduce pollutants in the feed gas/air at a rate 50 times higher than activated carbon at room temperature[2].



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This catalyst increases the effectiveness and reactivity of air purification systems.



Benefit Summary: 

This novel catalyst has the potential to improve indoor and outdoor air quality by removing and neutralizing pollutants at the source and in structures. The material can remove and degrade multiple pollutants 50 times more effectively than activated carbon filtration. Additionally, these manganese oxide/gold mesoporous composites are rechargeable, reducing resource consumption.


Risk Summary: 

While Manganese oxide gold catalysts reduce compounds harmful to human and environmental health, they can create environmentally damaging compounds as a product. One of the main products of the chemical reduction of volatile organic compounds and non-combusted hydrocarbons by manganese oxide/gold catalysts is carbon dioxide. Carbon dioxide is a major product of the catalysis of sulfur dioxide and nitrogen oxides as well. Carbon dioxide is also a greenhouse gas, and is one of the main greenhouse gases implicated in anthropogenic climate change. Depending on the scalability of manganese oxide/gold composite catalysts, this material may only trade one environmental and human health problem for another. Additionally, the manufacturing process used to create this novel catalyst also poses potential risks to human health. Gold nanoparticles have shown the potential for cytotoxixty and nephrotoxicity. Small aspect nanoparticles have the potential to penetrate cellular structures, with gold in particular showing the tendency to accumulate in renal and white blood cells in various studies.

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