Adsorption of hydrogen fluoride onto activated carbon under vacuum conditions: Equilibrium, kinetic and thermodynamic investigations

Abstract

In this study, the adsorption of HF gas by three types of activated carbon has been investigated under vacuum condition. The effects of experimental parameters such as initial pressure of the HF gas, contact time and temperature on adsorption process have been investigated. The results showed that the adsorption of the HF gas onto activated carbon increased by increasing initial pressure of gas, while it decreased with increase in temperature. The Freundlich isotherm model fitted the equilibrium data better than the other isotherm models. Using Langmuir isotherm model, the maximum adsorption capacities of the first type, the second type and third type of activated carbon were 226.4, 268.8 and 258.9 mg/g, respectively. Experimental data were also evaluated in terms of kinetic characteristics of adsorption and it was found that the adsorption process followed well pseudo-second-order kinetics. Thermodynamic parameters, the change of free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) of adsorption were calculated at the temperature range of 28-55°C. The results showed that the adsorption of HF on activated carbon is feasible, spontaneous and exothermic.

Keywords

• activated carbon
• hydrogen fluoride
• adsorption
• kinetic
• thermodynamic