Adsorption of Pb(II) from Aqueous Solutions by Chemically Modified Zeolite supported Carbon Nanotubes: Equilibrium, Kinetic, and Thermodynamic Studies

Abstract

Zeolite supported carbon nanotubes (ZCNTs) were synthesized by the catalytic chemical vapor deposition (CCVD) method. The physical and chemical properties such as surface area, pore diameter, surface functional groups, and total acidic and basic sites of the ZCNTs were studied. They were employed as adsorbent to study the adsorption characteristics of Pb(II) in aqueous solution. The adsorption of Pb(II) increase with an increase of contact time and temperature and reaches equilibrium within 80 min. The maximum removal of Pb (II) was found at pH 5.0. The kinetic data are analyzed using the pseudo-first, second-order kinetics, and intra particle diffusion. The equilibrium data are analyzed through Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models. The results have shown that the pseudo-second-order model fits the experimental data very well. The Langmuir model provides a best correlation with an adsorption capacity of 55.74 mg/g at 313 K. The thermodynamic properties ΔG^o, ΔH^o, and ΔS^o showed that adsorption of Pb (II) onto ZCNTs was found to be spontaneous, endothermic and feasible in the temperature range of 293–313 K. The ZCNTs possess higher Pb(II) sorption capacities, hence are a more promising Pb(II) adsorbent in water and useful in wastewater treatment.

Keywords:

• adsorption
• carbon nanotubes
• isotherms
• lead
• thermodynamics

ACKNOWLEDGEMENTS

One of the authors, D. K. Venkata Ramana, would like to thank the UGC, New Delhi, for awarding him with a Research Fellowship (UGC-I (6)/RFSMS/Chemistry) which enabled him to take up the present work.