Equilibrium and Kinetic Adsorption of Hydrogen Fluoride onto Zeolite 3A

Abstract

Equilibrium and kinetic adsorption behaviours of hydrogen fluoride (HF) onto zeolite 3A were investigated under different temperatures (298–338 K) and pressures (0.15–1.1 bar). The HF adsorption isotherms on zeolite 3A were well described by the Dubinin–Astakhov (DA) model. The isosteric heat of HF adsorption was calculated based on the DA model and Clausius–Clapeyron equation, and different kinetic models were used to analyze the HF adsorption kinetic. The results showed HF adsorption isotherms are type I of the IUPAC classification. The maximum adsorption capacities by the DA model are 0.443–0.5631 mg/g. The $H_{st}$ values decrease with increasing surface loading indicating the surface energy heterogeneity of zeolite 3A. The HF adsorption kinetics on zeolite 3A follows simple first-order kinetics. The calculated film diffusion parameter $B_t$ values show nonlinear characteristics with time. The order of magnitude of interparticle HF diffusion coefficient $D_c$ is 10−9 m2/s. The higher pressure and temperature are in favour of HF diffusion. The intraparticle diffusion curves for HF adsorption on zeolite 3A show quart-linear characteristics, indicating the presence of four consecutive HF adsorption steps including film diffusion, interparticle diffusion, intraparticle diffusion, and surface adsorption. The intraparticle diffusion is a rate-controlling stage.