Effects of airborne contaminant exposure on the physical properties and filtration performance of activated, impregnated carbon

The effects of airborne contaminant exposure in humid air on the physical properties and filtration capabilities of a copper/zinc/molybdenum impregnated carbon were investigated. The impregnated carbon was exposed individually to CO2, NH3 and NO2 in humid air, then evaluated for changes in metal speciation, metal distribution, porosity and water-uptake. The exposed impregnated carbon was further evaluated for changes in its ability to remove SO2 and cyclohexane from air streams. Exposure to CO2 did not impact the physical properties of the impregnated carbon, with changes in filtration performance were not evident. NH3 exposure resulted in the formation of metal amine complexes, which led to a migration of impregnants from within the pores of the carbon granule to the external surface. NH3 exposure increased SO2 filtration while decreasing cyclohexane filtration. The decrease in cyclohexane filtration was attributed to an increase in water uptake and a decrease in porosity. NO2 exposure significantly decreased the porosity of the carbon substrate while increasing the amount of surface oxygen. The increased surface oxygen greatly increased water uptake. NO2 exposure greatly reduced the SO2 breakthrough time and the ability of the material to remove cyclohexane.