Indoor Air Purification of Volatile Organic Compounds (VOCs) Using Activated Carbon, Zeolite, and Organosilica Sorbents

Indoor air pollution is a complicated problem involving a mix of many diverse contaminants that can negatively affect human health at elevated concentrations. Volatile organic compounds (VOCs) are some of the more toxic chemicals detected in indoor air. We evaluated the performance of materials commonly found in commercial air purifiers (activated carbon and zeolite clay) and a novel organosilica for their ability to remove VOCs from indoor air. Data from batch sorption experiments with toluene and benzene were modeled using Freundlich, Langmuir, and Temkin isotherm fitting techniques to quantify important sorption parameters. A new experimental technique was developed for conducting in situ gas chromatography measurements of batch sorption experiments in 20 mL glass vials that allowed for direct gas measurement after sorption without any further sample processing. Samples were analyzed for the VOC concentration remaining in the vial using gas chromatography with a flame ionization detector (GC-FID). The maximum adsorption capacity of activated carbon for toluene and benzene was 46.9 and 55.5 mg/kg, respectively, according to Langmuir adsorption isotherm fits. The adsorption capacities of organosilica for toluene and benzene were 3.49 and 2.05 mg/kg, respectively. Zeolite yielded minimal adsorption capacity compared with the two other sorbents. Projections from the experimental sorbent capacities indicate that under normal operating conditions (10 m3 with four air changes per hour and 200 cubic feet per minute), an air purifier filter could remove 30 ppb of VOCs for up to 690 days.