Modeling the Temperature Dependence of Adsorption Equilibriums of VOC(s) onto Activated Carbons

In order to optimize the efficiency of the removal of volatile organic compounds (VOCs) by adsorption onto activated carbon beds, process simulations taking into account exothermicity effects are helpful. Significant temperature increases may arise in the bed during the VOC adsorption cycle, especially when high concentrations have to be treated. Consequently, reliable and easy-to-handle isotherms remain a key hurdle to build realistic models. In this study, adsorption models were tested to describe a set of experimental data obtained for three VOCs (acetone, ethyl formate, and dichloromethane) adsorbed onto five commercial activated carbons at four different temperatures (20, 40, 60, and 80 degrees C). A new expression of the Freundlich equation [q(e)=(a(1)T+a(2)T(2))C-e(1/n(f))] was shown to be statistically the most efficient to describe the adsorption isotherms of VOCs, single or in mixtures. A second-order polynomial temperature-dependence was introduced in this expression. The so-adapted Freundlich relationship gave a mean coefficient of determination of 0.97 for single-component adsorption and a correlation coefficient of 0.98 for binary mixtures.