Equilibrium and Kinetic Adsorption of Hydrogen Fluoride onto Zeolite 3A

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) m(2)/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.