Indoor Air Purification via Low-Energy, in-Situ Regenerated Silica-Titania Composites

“Sick building syndrome,” used to describe acute negative health effects linked to time spent in a building, has been related to poor indoor air quality.  Similarly, poor aircraft cabin air quality has been identified as a cause of negative health effects on pilots and flight crews, leading to numerous studies on “aerotoxic syndrome.”  These symptoms can pose a serious threat if experienced by pilots and/or crew during flight. Volatile organic compounds (VOCs) are a major source of indoor air pollution.  Technologies that can safely, economically, and effectively degrade VOCs from indoor air are necessary to protect human health. Silica-Titania Composites (STCs), an innovative technology developed at the University of Florida, have been successfully demonstrated in bench- and pilot-scale tests to remove VOCs from the air and have been commercialized for gas-phase mercury removal at a chlor-alkali facility.  Sol-gel Solution LLC (Sol-gel) has licensed the technology for commercialization. Although STCs are well suited for numerous indoor air applications, this project will focus on a system for purification of aircraft cabin air using the STC in a manner that will minimize energy input and oxidation by-product generation in closed environments.  The current norm is to use sorbent filters, which simply transfers a gas-phase contamination problem to the solid phase.  These filters are bulky, and must be disposed of when “saturated.” STCs are normally employed as a packed bed of pellets that is continuously irradiated with UV light, which promotes the simultaneous adsorption and oxidation of VOCs.  Oxidation of VOCs in closed environments raises concerns about the release of oxidation intermediates.  Because STCs have high adsorption capacity for several contaminants, continuous irradiation is not necessary for pollutant removal.  Sol-gel proposed to operate the STC in adsorption mode (without irradiation) during flight, with periods of regenerative irradiation to oxidize adsorbed pollutants when passengers have disembarked.  The initial target market is the airline industry because the need is most pressing in this arena.  This system, however, would work equally well for residential and commercial indoor air purification.  The scope of work involves determining STC adsorption capacity, the required regeneration frequency and duration, and the quantification of oxidation by-products.  Additionally, life cycle assessment of the proposed system will be carried out.  Because of the low energy requirement, long lifetime, and simple regeneration, the proposed approach promises to be preferable to other technologies.