Role of tailored surface of activated carbon for adsorption of ionic liquids for environmental remediation

The surface of activated carbon (AC) was oxidized using different oxidizing agents (nitric acid and sodium hypochlorite). This modified AC (mAC) was used for the adsorption of ionic liquids (ILs). These mACs were characterized before and after adsorption of ILs using different techniques. The surface area of AC decreased after oxidation, but total acidity increased as compared to untreated AC. The pH of point zero charge of ACs was also decreased after oxidation. The role of adsorbents and its interaction with ILs have been investigated using batch adsorption experiments. Both the alkyl chain length and cation type of ILs affected their adsorption onto ACs; long alkyl chain showed higher adsorption. The pH study showed higher adsorption at higher pH as compared to lower pH value. The pseudo-second-order model was best fitted to the kinetic adsorption data, and Langmuir isotherm model was best fitted on isotherm data. The overall adsorption process was controlled by intra-particle diffusion and external mass transfer. The adsorption results obtained in this study showed comparably higher value with published literature.

Keywords
Adsorption properties; Aqueous solution; Isotherms models; Surface functional groups