Assessing the efficiency of zeolites in BTEX adsorption: Impact of pore structure and humidity in single and multicomponent systems

Abstract

Among volatile organic compounds (VOCs), benzene, toluene, ethylbenzene and o-xylene (BTEX) have attracted global attention because of their high toxicity to the environment and human health. Adsorption is considered one of the most efficient, simple and low-cost technology for VOC pollution control and zeolites have been commonly used as adsorbent for this purpose. However, the evaluation of the performance of zeolites in the adsorption of BTEX under realistic conditions such as the presence of humidity or multicomponent systems has been poorly addressed. In this study, the adsorption capacity of BTEX of seven zeolites belonging to the structural families LTA, MFI, BETA, MOR and FAU have been investigated. Zeolites have been characterized by X-ray fluorescence and nitrogen sorption measurements. The relationship between the adsorption capacity and physicochemical parameters was investigated. It was found that MFI structure was the best adsorbent for benzene and toluene reaching an adsorption capacity of 69.2 mg/g. Whereas FAU structure exhibited preference to trap ethylbenzene and o-xylene adsorbing up to 93.8 mg/g. Specific surface area and pore diameter of zeolites were found to be the most important parameter for BTEX adsorption. The properties of the adsorbate (molecular structure, polarity and boiling point) played also a key role in adsorption. Si/Al ratio was a key factor in determining adsorption performance under humidity conditions with the best adsorption capacity reaching 16.9 mg/g. In multi-component system, the adsorption capacity of zeolites decreased more than 14 %. The results obtained may guide to select proper adsorbent for BTEX in real applications.