Using a novel adsorbent macrocyclic compound cucurbit[8]uril for Pb2+ removal from aqueous solution

In this study, cucurbit[8]uril(CB[8]) was utilized as a kind of new adsorbent to remove Pbions from aqueous solution. With the solution p H increased from 2 to 6, the removal efficiency of adsorption increased from 55.6% to 74.5%correspondingly. The uptake of Pbincreased rapidly in the initial 30 min, and then the adsorption rate became slower. The Pseudo-second order model could be used to interpret the adsorption kinetics satisfactorily;and the rate determining step in Pbadsorption onto CB[8] was the external mass transfer step. Equilibrium isotherm study reveals that the Langmuir model gave a better fitting result than Freundlich model. The maximum adsorption capacity calculated by the Langmuir model was 152.67 mg/g for 298 K, 149.70 mg/g for 313 K and 136.42 mg/g for 323 K, respectively.The adsorption is a spontaneous process of exothermic nature. The effect of the adsorbent dosage and the influences of solution p H and co-existing cations were also investigated.The CB[8] was synthesized and characterized byH NMR, IR, ESI-MS spectra, SEM-EDAX,Zeta-potential and BET-analysis. The adsorption mechanism was due to the coordination between CB[8] molecule and Pbions.