An inverse gas chromatography study of the adsorption of organics on zeolite and zeolite/iron oxyhydroxide composite at the infinite and finite surface coverage

Abstract

The surfaces of natural (NZ) and zeolite/iron oxyhydroxide composite (ZFe) samples were analyzed by means of inverse gas chromatography (IGC) using adsorption data of organic non-polar and polar probes, in the infinite and finite-dilution regimes, in the temperature range 483-513 K. The dispersive components of the free energy of adsorption, ?S, determined by the Gray method, decreased with increasing temperature for both zeolites. The specific interactions were characterized by the specific free adsorption energy, ?GaS , the specific enthalpy of adsorption, ?HaS , as well as the donor and acceptor interaction parameters (KA, KD) and the basic character of the NZ and ZFe was evidenced. The adsorption isotherms of n-hexane (n-C6H14), benzene (C6H6), chloroform (CHCl3) and tetrahydrofuran (THF) were determined under finite surface coverage and used to estimate the specific surface area and the adsorption energy distribution. The adsorption capacity of the ZFe was higher than for NZ for all the investigated adsorbates. The specific surface areas and pore size distributions were also determined using nitrogen adsorption-desorption isotherms, i.e., the BET method. It was observed that the nature of the adsorbate and the properties of the solid surface of the initial and modified samples governed the uptake of adsorbates.