A STUDY OF RESPIRATOR CARBONS

Abstract

Porous, high surface area activated carbon (AC) can be used to remove certain irritating and toxic gases from contaminated air streams. Impregnating AC with carefully selected chemicals can improve ACs adsorption capacity for certain gases and provide adsorption capacity for gases that un-impregnated AC cannot fi lter. Impregnated activated carbons (IACs) and ACs can be used as the active component in respirators. Comparative studies of di fferent commercially available AC samples and of IAC samples, prepared from a wide variety of di fferent chemicals, were performed. The gas adsorption capacity of the samples was tested using sulfur dioxide (SO2), ammonia (NH3), hydrogen cyanide (HCN) and cyclohexane (C6H12) challenge gases and compared to results obtained from a commercially available broad spectrum respirator carbon. The samples were characterized using wide angle x-ray di raction (XRD), small angle x-ray scattering (SAXS), nitrogen adsorption isotherms, thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). Highlights of this work include the discovery of a IAC sample prepared from zinc nitrate (Zn(NO3)2) and nitric acid (HNO3) that, after heating at 180 C under argon, had overall dry gas adsorption capacity that was greater than the commercially available sample. The importance of pore size on the C6H12 adsorption capacity of AC was demonstrated using SAXS and nitrogen adsorption data. A relationship between decreased humid C6H12 capacity and pre-adsorbed water was shown using SAXS, TGA and gravimetric studies.