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In this study, introduction of acidic functional groups onto a carbon surface and their removal were carried out through two oxidation methods and outgassing to investigate the adsorption mechanism of aromatic compounds which have different polarity (benzene and nitrobenzene). Adsorption experiments for these aromatics in aqueous solution and n-hexane solution were conducted in order to obtain the adsorption isotherms for commercial activated carbon (BAC) as a starting material, its two types of oxidized BAC samples (OXs), and their outgassed samples at 900°C (OGs). Adsorption and desorption kinetics of nitrobenzene for the BAC, OXs and OGs in aqueous solution were also examined. The results showed that the adsorption of benzene molecules was significantly hindered by abundant acidic functional groups in aqueous solution, whereas the adsorbed amount of nitrobenzene on OXs gradually increased as the solution concentration increased, indicating that nitrobenzene can adsorb favourably on a hydrophilic surface due to its high dipole moment, in contrast to benzene. In n-hexane solution, it was difficult for benzene to adsorb on any sample owing to the high affinity between benzene and n-hexane solvent. On the other hand, adsorbed amounts of nitrobenzene on OXs were larger than those of OGs in n-hexane solution, implying that nitrobenzene can adsorb two adsorption sites, graphene layers and surface acidic functional groups. The observed adsorption and desorption rate constants of nitrobenzene on the OXs were lower than those on the BAC due to disturbance of diffusion by the acidic functional groups.

a), b) and Motoi Machida a),b) Melamine sponge was used to prepare carbonized materials for the adsorption of nitrate ions. Carbonization and ZnCl 2 activation of the melamine sponge were simultaneously conducted at 500 °C to develop porosity. In addition, a subsequent CH 3 I treatment was used to modify its surface. A ZnCl 2 impregnation ratio of 6 g/g (Z6) was the best condition for the removal of nitrate ions and a further increase in nitrate adsorption was observed as a result of the CH 3 I treatment (Z6-Q). Z6-Q exhibited a superior nitrate ion adsorption capacity of 0.81 mmol/g which was approximately 1.3 times that of Z6. The adsorption of nitrate ions on the prepared samples was found to be the highest under acidic conditions, while basic conditions were not suitable due to inhibition by the hydroxide ions. In the pH range 1.5 to 2.5, the initial concentration of chloride ions increased and caused competition with nitrate ion adsorption. Based on the adsorption isotherms of nitrate ions, the adsorption processes were well fitted to the Langmuir equation. The TG/DTG profile revealed thermal decomposition of quaternary ammonium and adsorbed nitrate ions. After 3 regeneration cycles, the amounts of adsorbed nitrate ions for Z6 and Z6-Q were respectively 95 and 98% of the initial values, implying that the adsorbents are recyclable.