Indoor air pollution control: Formaldehyde adsorption by zeolite rich materials

Formaldehyde is a carcinogenic byproduct emitted from resins in plywood, hardwood paneling, and carpets. This pollutant is commonly found in indoor environments and as such is purported to be the main causative agent of sick building syndrome. Building materials such as paneling and coating with highly adsorptive properties given by zeolites incorporated into their composition can help curb indoor air pollution. In this research zeolites were synthesized and tested for their ability to adsorb formaldehyde from the air. Class F fly ash, a waste product from coal combustion, and metakaolinite, a clay material, were mixed with sodium hydroxide solutions to produce zeolites. Samples were mixed as pastes and reacted as a function of time and temperature. Zeolite A, faujasite, analcime, and other mixed phases were obtained. Samples were characterized by X-ray diffraction and scanning electron microscopy. To test the ability of materials at cleaning formaldehyde from the air, samples were put in contact with a "polluted" air stream. Compressed air was mixed with the gas phase above a volume of a 10% formalin solution used as permanent source of formaldehyde. Air passed through an adsorption cell consisting of concentric layers coated with zeolite powders. Formaldehyde removal was monitored by observing the change of its infrared spectrum with time by means of Fourier transform infrared spectroscopy. Formaldehyde spectral peaks completely disappeared within few minutes of contact, dropping to "zero" percent formaldehyde. Results obtained from this preliminary study demonstrate the feasibility of using synthesized zeolites to improve indoor air quality.