Measurement of the impedance change of impregnated activated carbon during exposure to SO2 vapors at ambient temperatures

By Rubel, Glenn O.; Peterson, Gregory W.; Fletcher, Nicole K.; III, Julian E. Parker & Jeffers, Robert B.
Published in Carbon NULL 2009

Abstract

The impedance of impregnated carbon is measured in real time during exposure to SO2 vapors at ambient temperatures using a plug flow reactor and an impedance monitor. Impedance measurements are accomplished using a dual parallel plate mesh electrode configuration that measures the electrical conductivity of the carbon bed using an impedance analyzer operating at 10 Hz. It is observed for all impregnated carbon samples undergoing SO2 exposure the carbon impedance undergoes an initial increase followed by a longer lasting characteristic decrease. The rate of the initial impedance increase appears to be proportional to the SO2 partial pressure, while the impedance drops more quickly with increasing relative humidity and additive concentration. From these findings, along with XPS measurements to identify the chemical composition of the carbon bed, it is postulated that the SO2 interaction with impregnated activated carbon is governed by an initial physical adsorption of SO2 vapors onto the activated carbon followed by a catalytic oxidation of SO2 to SO3 and eventually a conductive sulfate-containing acid like H2SO4.

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