Examining the role of surface oxygen-containing functional groups in liquid-phase adsorptive denitrogenation on activated carbons by a combination of TPD analysis and multiple linear regression

In order to fundamentally understand the role of surface oxygen-containing functional groups in liquid-phase adsorptive denitrogenation on activated carbons, the adsorptive denitrogenation performance of twelve activated carbons was evaluated in a bath system using the solutions containing quinoline and indole, respectively, in decane. The adsorption isotherms were obtained and the adsorption parameters (K and qm) in the Langmuir isotherm equation were estimated. The surface chemical properties of the activated carbons, including the type and concentration of the oxygen-containing functional groups on the surface, were characterized by the temperature programmed desorption (TPD) on the basis of CO2- and CO-evolution profiles. The adsorption performance of the activated carbons and their physical and chemical properties was conducted by a multiple linear regression method. It was found that the type and amount of the oxygen-containing functional groups play a decisive role in adsorption denitrogenation on the activated carbons. The acidic, especially the stronger acidic, functional groups, such as carboxyl and anhydride, appear to show higher responsibility for adsorption of the basic nitrogen compounds, while the basic oxygen-containing groups have more contribution to adsorption of the neutral nitrogen compounds.