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

Area of Science:

• Environmental Chemistry
• Materials Science
• Adsorption Science

Background:

• Lead (Pb²⁺) contamination in aqueous solutions poses significant environmental and health risks.
• Developing efficient and cost-effective adsorbents is crucial for heavy metal removal.
• Cucurbiturils are macrocyclic compounds with potential applications in molecular recognition and separation.

Purpose of the Study:

• To investigate the efficacy of cucurbit[8]uril (CB[8]) as a novel adsorbent for Pb²⁺ removal from aqueous solutions.
• To elucidate the adsorption kinetics, isotherm, and thermodynamic properties of Pb²⁺ onto CB[8].
• To explore the influence of operational parameters like pH and co-existing ions on Pb²⁺ adsorption.

Main Methods:

• Synthesis and characterization of cucurbit[8]uril (CB[8]) using techniques including ¹H NMR, IR, ESI-MS, SEM-EDAX, Zeta-potential, and BET analysis.
• Batch adsorption experiments were conducted to evaluate Pb²⁺ removal efficiency under varying conditions (pH, temperature, adsorbent dosage).
• Adsorption kinetics and isotherm data were analyzed using Pseudo-second order and Langmuir/Freundlich models, respectively.

Main Results:

• Cucurbit[8]uril (CB[8]) demonstrated significant Pb²⁺ removal, with efficiency increasing from 55.6% to 74.5% as pH rose from 2 to 6.
• Adsorption followed Pseudo-second order kinetics, indicating external mass transfer as the rate-determining step.
• The Langmuir model provided a better fit, with maximum adsorption capacities of 152.67 mg/g at 298K, 149.70 mg/g at 313K, and 136.42 mg/g at 323K.
• Adsorption was found to be a spontaneous and exothermic process, driven by coordination between CB[8] and Pb²⁺.

Conclusions:

• Cucurbit[8]uril (CB[8]) is a highly effective adsorbent for removing Pb²⁺ from aqueous solutions.
• The adsorption mechanism involves coordination interactions between the adsorbent and Pb²⁺ ions.
• CB[8] shows promise as a sustainable material for heavy metal remediation in water treatment applications.