Regeneration of Impregnated Activated Carbon after Aging

Abstract

Impregnated activated carbon (IAC) is an efficient adsorbent for the filtration of hazardous gases from the air. However, it tends to lose its efficiency after exposure to high humidity, where it adsorbs water molecules. Water adsorption causes changes in metal impregnation, resulting in a loss of adsorption efficiency for certain toxic gases, particularly gases that are adsorbed via chemisorption. Here, an innovative method was developed for the regeneration and reactivation of aged IAC. The method is based on dripping a regeneration solution composed of ammonium hydroxide and ammonium carbonate onto the aged IAC. The developed regeneration method was applied to ASZMT, a common commercially used IAC, that had undergone accelerated aging for six months. After the regeneration process, the protection capacity of the IAC against cyanogen chloride (CK) and toluene was almost fully restored to its initial value. Elemental analysis by energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) showed that after the regeneration procedure, the concentrations of zinc and copper on the external surface of the IAC were decreased. This provides evidence that they were partially incorporated back into the pores. It is reasonable to believe that the developed method can be applied to IACs other than ASZMT impregnated with different kinds of materials. The implementation of this method has economic and environmental consequences. In the future, it may allow the reuse of aged IAC and even the restoration of filters.