Liquid phase removal of propanethiol by activated carbon: Effect of porosity and functionality

The removal of propanethiol from liquid phase (1-hexene as solvent) at room temperature has been investigated using different activated carbons. The experimental results show that both the porous structure and surface chemistry of the activated carbon influence the kinetics of propanethiol removal and the total removal capacity (adsorption plus oxidation to dipropyl disulfide). In this sense, while the microporous structure of the carbon is the main parameter defining the removal kinetics, the presence of oxygen functionalities on the carbon surface affects the extent of propanethiol oxidation to dipropyl disulfide and, consequently, the total removal capacity. An oxidation treatment with HNO3 of selected carbons confirms the promoting effect of the oxygen surface groups in this oxidation process. However, this study shows that the oxidation capacity of the activated carbons is not defined by the amount but mainly by the nature of the oxygen surface groups. The high stability of these groups after a heat treatment at 973 K in a He flow indicates that the conjugated ketone groups (quinone groups) may be responsible of the oxidation of propanethiol to dipropyl disulfide.