Adsorption characteristics of SO2 on activated carbon prepared from coconut shell with potassium hydroxide activation.

The adsorption characteristics of SO2 were studied with KOH-impregnated granular activated carbon (K-IAC). To confirm selective SO2 adsorptivity of K-IAC using a fixed bed adsorption column, experiments were conducted on the effects of KOH and of linear velocity, temperature, and concentration. In addition, changes in features before and after adsorption were observed by utilizing FTIR, XRD, ToF-SIMS, and AES/SAM, examining the surface chemistry. K-IAC adsorbed 13.2 times more SO2 than did general activated carbon (GAC). The amount of SO2 adsorbed increased as linear velocity and concentration increased and as temperature decreased. At lower temperature, the dominant reaction between KOH and SO2 produces K2-SO3 and H2O. Any H2O remaining on the surface is converted into H2SO4 as SO2 and O2 are introduced. Then, the KOH and SO2 reaction produces K2SO4 and H2O. The surface characterization results proved that adsorption occurred through chemical reaction between KOH and SO2. The SO2 adsorbed K-IAC exists in the form of stable oxide crystal, K2SO3 and K2SO4, due to potassium. The basic feature given to the surface of activated carbon by KOH impregnation was confirmed to be acting as the main factor in enhancing SO2 adsorptivity.