Adsorption of vapor-phase VOCs (benzene and toluene) on modified clays and its relation with surface properties

A mexican bentonite was used to prepare three modified clays: an organoclay (OC-CPC) by intercalating cetylpyridinium chloride (CPC), an aluminum-pillared clay (Al-PILC), and an inorganic-organic clay (IOC-CPC) prepared from Al-PILC intercalating CPC. The infrared and thermogravimetric analyses enabled us to differentiate between, the structures obtained. Interlayer distance was assessed through. X-ray diffraction; the OC-CPC was the clay that showed the highest value (12.4 Å). The natural clay's specific area was 43.5 m²/g, increasing to 157.2 m²/g for Al-PILC. The OC-CPC and IOC-CPC specific areas were 13.27 m²/g and 14.5 m²/g, respectively. Al-PILC was a microporous material; whereas natural clays, OC-CPC and IOC-CPC were non-porous materials. Tolne and benzene adsorption on OC-CPC was higher than in IOC-CPC and Al-PILC. Natural clay showed no adsorption capacity for these compounds. Comparison of the GC retention times for non polar and low-polarity compounds (octyne and benzene) in columns packed with OC-CPC and a commercial non polar column (squalene) showed that the OC-CPC possessed a higher organophilic (non polar) nature than squalene. This explains the higher benzene and toluene adsorption capacity of the OC-CPC compared with the other modified clays. The toluene and benzene adsorption isotherm for OC-CPC was well-described by the GAB (Guggenheim-Anderson-De Boer) model for the whole range of relative pressure used in this work (0-0.9) describing multilayer adsorption and capillary condensation.