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

Sun, Xuzhuo, Li, Bo, Wan, Dongjin, Wang, Ning
Journal of environmental sciences (China) 2016 v.50 pp. 3-12
adsorbents, adsorption, aqueous solutions, cations, electrospray ionization mass spectrometry, heat production, lead, macrocyclic compounds, mass transfer, models, nuclear magnetic resonance spectroscopy, pH, sorption isotherms, zeta potential
In this study, cucurbit[8]uril (CB[8]) was utilized as a kind of new adsorbent to remove Pb²⁺ ions from aqueous solution. With the solution pH increased from 2 to 6, the removal efficiency of adsorption increased from 55.6% to 74.5%correspondingly. The uptake of Pb²⁺ increased rapidly in the initial 30min, 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 Pb²⁺ adsorption 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 152.67mg/g for 298K, 149.70mg/g for 313K and 136.42mg/g for 323K, respectively. The adsorption is a spontaneous process of exothermic nature. The effect of the adsorbent dosage and the influences of solution pH and co-existing cations were also investigated. The CB[8] was synthesized and characterized by ¹H 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 Pb²⁺ ions.