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Thermodynamic Evidence of Flexibility in H2O and CO2 Absorption of Transition Metal Ion Exchanged Zeolite LTA

Abstract

Gas adsorption calorimetry has been emplyed to probe the intercation of water and carbon dioxide with transition metal ion (TM = Mn2+, Fe2+, Co2+, Cu2+, Zn2+) exchanged zeolite A. There appears to be a two phase region, indicative of a guest-induced flexibiity transition, separating hydrated zeolite A and its dehydrated form, both of which have variable water content in the single phase region. The differential enthalpy of absorption as a function of water loading directly identifies different strengths of multiple interactions along with possible binding mechanisms Zn-A and Mn-A exhibit the highest water absorption with most exothermic initial emthalpies of -125.28 ± 4.82 and -115.30 ± 2.56 kJ/mol. Zn-A and Mn-A also show moderately good capture ability for CO2 with zero coverage exothermic enthalpies of -55.59 ± 2.48 and -−44.07 ± 1.53 kJ/mol. The thermodynamic information derived from differential enthalpy, chemical potential and differential entropy elucidated the multistage interactive behavior of the small guest molecules (H2O/CO2) and the ion exchanged frameworks.

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Publication details

The article was received on 06 Dec 2017, accepted on 11 Jan 2018 and first published on 11 Jan 2018


Article type: Paper
DOI: 10.1039/C7CP08188J
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Thermodynamic Evidence of Flexibility in H2O and CO2 Absorption of Transition Metal Ion Exchanged Zeolite LTA

    X. Guo, L. Wu and A. Navrotsky, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C7CP08188J

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