Investigating the interaction of two asymmetric dioxins with FAU 13X zeolites using calorimetry and solid-state NMR

• Adsorption of two characteristic dioxins in competition with isooctane was studied.
• Adsorption enthalpies were determined by microcalorimetry.
• Presence of small amounts of water does not affect dioxin adsorption.
• DNP NMR shows dioxin adsorption with no catalytic conversion.

We report on the characterization of dioxin adsorption, notably 2,3-DCDD and 1,2,3,4-TeCDD, from isooctane onto zeolite FAU 13X Na+ and FAU 13X La3+, with 80% Na+- La3+ exchange level. Adsorption isotherms showed extreme affinities of 2,3-DCDD towards FAU 13X Na+ and 1,2,3,4-TeCDD towards FAU 13X La3+ in the experimentally accessible concentration range, which is limited by dioxin solubility in isooctane.Thermogravimetric studies were employed to understand the effect of water content level of zeolites onto the affinity and capacity of adsorption, but also to determine the temperature range of eventual dioxin regeneration.Moreover, microcalorimetric investigations indicated that high dioxin adsorption affinities of 2,3-DCDD towards FAU 13X Na+ and 1,2,3,4-TeCDD towards FAU 13X La3+, respectively, were combined with quite different levels of adsorption enthalpies. Cross polarization magic angle spinning (CP-MAS) NMR experiments recorded with dynamic nuclear polarization (DNP) revealed that 1,2,3,4-TeCDD was adsorbed simultaneously with isooctane in the micropores of the zeolites, without chemical alteration.

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