Adsorption of imidazolium-based ionic liquids from aqueous solution onto cellulose-derived activated carbon materials

Carbonaceous adsorbents were prepared from hydrothermal carbonization of cellulose followed by chemical activation under various conditions. The effect of the surface chemistry of the prepared adsorbents on the adsorption of ionic liquids (ILs) with various chemical structures was investigated. Here, the adsorption of hydrophobic ILs from aqueous streams was enhanced by increasing the activation temperature thus reducing the number of oxygenated groups on the surface of the carbonaceous adsorbent. In addition, the adsorption capacity of hydrophilic ILs on carbon materials was increased by increasing the KOH/HC weight ratio used for activation. For the prepared carbon material adsorbents, the adsorption capacities of imidazolium-based ILs, with different anions, onto the adsorbent increased with increasing hydrophobicity of the IL anions in the following order Cl− < TFA− < [BF4]− < OTf− < [PF6]− < NTf2−. Therefore, the adsorption capacities of carbon materials for ILs can be tailored through alteration of their surface chemistry by changing activation conditions.