Na⁺/Mordenite Interaction Energy Determined by Thermally Stimulated Depolarization Current

Abstract

The evolution of thermally stimulated depolarization current (TSDC) measured on a mordenite Na zeolite is examined as a function of the Na+ exchange degree. According to this investigation, the dipolar reorientation is due to Na+, and the TSDC signal analysis leads to an assessment of the interaction energies between the hopping Na+ ions and the zeolitic lattice. The values of these energies are found to be between 0.7 and 0.9 eV. According to the Na+ exchange degree and the nature of the occupied Na+ sites, a quantitative and qualitative characterization of each site is given.

Analysis of Thermally Stimulated Depolarization Currents (TSDC) Measured on Exchanged Clays

“…Thermally stimulated depolarization current technique (13,14) is a method well suited to determining some energetic and thermodynamic characteristics of solids using the recent approach of the analysis of the distribution of the relaxation times (ARDT) (8).…”

“…Its performance can be markedly increased when used in a fractional analytical mode (relaxation map analysis, RMA). It allows the analysis of the fractionated peaks obtained by means of the "thermal windowing technique" according to a procedure previously described (8,15).…”

Insights into cation exchange selectivity of a natural clinoptilolite by means of dielectric relaxation spectroscopy

“…characterizes the system under study and, in the present case, can be related to the various crystallographic sites in which EFC are located [4,10,14] and around which they can hop. The fit of ) , ( " T f ε with eq.…”

“…When ) ( i E G ∆ is refined, it gives us access to the mean activation energy and the relative population characterizing each different types of ionic hop. This procedure was proved to be productive in many zeolites [4,10,14].…”

“…The relative area of each Gaussian function yields the relative population of cationic site, cf equation 4 [4,14,21]. Providing the incertitude due both to the experimental signal and to the fitting modus operandi, it can be concluded (see table 3) that, independently on their nature, the cations are equally distributed in these two sites.…”