Being one of the most important and widely-used gases in uranium conversion industry, Fluorine (F 2 ) is usually used to produce 18000-21000 tons of uranium hexafluoride per year worldwide which needs 6000-7000 tons of fluorine gas. The production of fluorine in nuclear industries is mainly based on the electrolysis of potassium anhydride difluoride which also leads to the production of hydrogen fluoride gas (HF) as an impurity. The amount of impurity of HF in the fluorine gas which is produced by the above mentioned reaction is in the range of 5-10 mole percent. In order to use fluorine gas in uranium conversion facilities, it is necessary to purify electrolysis product and decrease the amount of its HF to 0.2 mole percent. In uranium conversion industry, the fluorine gas is used as chemical raw material gas to produce UF 4 and UF 6 while its purity is very important. As a part of a main study, the purpose of the present paper is to investigate the process of HF adsorption on NaF pellets and to determine the corresponding adsorption isotherm in different operating conditions. To our knowledge, due to the very specific nature and applications of such studies and their results, very few data have been published in the literature. In a second part, the obtained results of this study are used in order to verify a mathematical model which has been developed for predicting the HF adsorption performance on NaF pellets in a fixed bed adsorber. In this study, the adsorption process of hydrogen fluoride, as an impurity in the process of fluorine production, on sodium fluoride pellets is experimentally studied in a lab-scale fixed bed adsorber. Also, the effects of some operating parameters including inlet concentration and inlet temperature of hydrogen fluoride on the adsorption process are intensively investigated. The data of adsorption are analyzed and correlated by Langmuir, Freundlich and Temkin isotherms. The adsorption capacity is found to be 1.908 and 0.750 gr HF/gr NaF by the Langmuir isotherm at 22 and 54°C, respectively. The favorable nature of adsorption which is expressed in terms of a dimensionless separation factor (R L ) is found to be more than 1 indicating an unfavorable adsorption. In addition, the data analysis shows that the Langmuir and Temkin isotherms fit the equilibrium isotherms better than that of Freundlich. Also a mathematical model for non-isothermal operation was established based on the conservation laws to illustrate the mechanism of gas-solid heat and mass transfer. The governing equations solved numerically and the accuracy of the model results were demonstrated by the fact that most of the predicted exit concentration of HF and breakthrough curves agreed well with the experimental data. After model validation software ......