Selective Adsorption of Phenol and Nitrobenzene by β-Cyclodextrin-Intercalated Layered Double Hydroxide: Equilibrium and Kinetic Study

Abstract

The composite of carboxymethyl-modified β-cyclodextrin-intercalated ZnAl-layered double hydroxide (CMCD-LDH) was investigated for selective adsorption of phenol (Ph) and nitrobenzene (NB). The Freundlich model can be used to describe satisfactorily the adsorption isotherms of Ph and NB. The adsorption capacity of CMCD-LDH for Ph and NB increases with the increase of temperature, indicating the endothermic nature of this sorption process. CMCD-LDH exhibits preferential adsorption for Ph over NB at pH 6.5 due to the selective recognition of the interlayer CMCD cavity. Pseudo-first-order and pseudo-second-order kinetic models were applied to simulate the kinetics of the adsorption process. The calculated qe values based on the pseudo-second-order model are much closer to the experimental data qe,exp. As a result, the pseudo-second-order kinetic model is more reasonable to describe the adsorption process of Ph and NB onto the CMCD-LDH composite. CMCD-LDH can be potentially applied in selective adsorption and separation of wastewater pollutants.