Adsorption of ionic liquids onto an activated carbon: kinetic modeling studies

In this study, the uptake of hydrophobic bromide-based ionic liquids (ILs) (imidazolium, pyrrolidinium, and pyridinium) from aqueous solutions onto granulated and fabric-based microporous activated carbons (ACs). Surface characterization study shows that both ACs have basic pHpzc, like 8.7 for granulated AC and 8.0 for fabric AC. Granulated AC have ten times higher phenolic groups 0.2 meq g−1 compared to fabric AC which is 0.03 meq g−1. The kinetics of adsorption was remarkably slower for ILs on granulated/fabric AC than milled one. We also studied the effect of AC size on the rate of adsorption in the operating conditions. In order to improve the adsorption kinetics of ILs with ACs, different phenomenological and empirical kinetic models like as pseudo-first order, Boyd model, pseudo-second-order diffusion model and Elovich were applied on the kinetic experimental data. The analysis of kinetic specified that the adsorption mechanism of ILs onto ACs is controlled mainly by the mass transfer through the pores of ACs. So, the selection of appropriate adsorbent particle size of AC plays a main role for the development of viable IL adsorption.