Adsorption Characteristics of Zinc (Zn²⁺) from Aqueous Solution by Natural Bentonite and Kaolin Clay Minerals: A Comparative Study

Tushar Kanti Sen, Chi Khoo

Department of Chemical Engineering, GPO Box U1987, Curtin University, Perth, 6845 Western Australia, Australia.

DOI: 10.4236/cweee.2013.23B001                

Abstract

Clay minerals are one of the potential good adsorbent alternatives to activated carbon because of their large surface area and high cation exchange capacity. In this work the adsorptive properties of natural bentonite and kaolin clay minerals in the removal of zinc (Zn²⁺) from aqueous solution have been studied by laboratory batch adsorption kinetic and equi- librium experiments. The result shows that the amount of adsorption of zinc metal ion increases with initial metal ion concentration, contact time, but decreases with the amount of adsorbent and temperature of the system for both the ad- sorbents. Kinetic experiments clearly indicate that adsorption of zinc metal ion (Zn²⁺) on bentonite and kaolin is a two-step process: a very rapid adsorption of zinc metal ion to the external surface is followed by possible slow decreas- ing intraparticle diffusion in the interior of the adsorbent. This has also been confirmed by an intraparticle diffusion model. The equilibrium adsorption results are fitted better with the Langmuir isotherm compared to the Freundlich model. The value of separation factor, R_L from Langmuir equation give an indication of favourable adsorption. Finally from thermodynamic studies, it has been found that the adsorption process is exothermic due to negative ?H⁰ accompa- nied by decrease in entropy change and Gibbs free energy change (?G⁰). Overall bentonite is a better adsorbent than kaolin in the the removal of Zn²⁺ from its aqueous solution.

Keywords

Metal Ion Adsorption; Clay Minerals; Kinetics; Isotherms

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	S. SenGupta and K. G. Bhattacharyya, “Adsorption of Ni (II) on Clays,” Journal of Colloid and Interface Science Vol. 295, No. 1, 2006, pp. 21-32. doi:10.1016/j.jcis.2005.07.073
[2]	T. K. Sen, and G. Dustin, “Adsorption of Zinc (Zn2+) from Aqueous Solution on Natural Bentonite,” Desalination, Vol. 267, No. 2-3, 2011, pp. 286-294. doi:10.1016/j.desal.2010.09.041
[3]	F. Arias and T. K. Sen, “Removal of Zinc Metal Ion (Zn2+) from Its Aqueous Solution by Kaolin Clay Mineral: A Kinetic and Equilibrium Study,” Colloids and Surfaces A: Vol. 348, 2009, pp. 100-108. doi:10.1016/j.colsurfa.2009.06.036
[4]	C. H. Weng and C. P. Huang, “Adsorption Characteristics of Zn (II) from Dilute Aqueous Solutions by Fly Ash,” Colloids Surf A, Vol. 247, 2004, pp. 137-143. doi:10.1016/j.colsurfa.2004.08.050
[5]	D. Mohan and K. P. Singh, “Single and Multicomponent Adsorption of Cadmium and Zinc Using Activated Carbon Derived from Bagassean Agricultural Waste,” Water Research, Vol. 36, 2002, pp. 2304-2318. doi:10.1016/S0043-1354(01)00447-X
[6]	A. K. Bhattacharya, S. N. Mandal and S. K. Das, “Adsorption of Zn (II) from Aqueous Solution by Using Different Adsorbents,” Chemical Engineering Journal Vol. 123, 2006, pp. 43-51. doi:10.1016/j.cej.2006.06.012
[7]	M. Mohammad, S. Maitra, N. Ahmad, A. Bustam, T. K., Sen and B. K. Dutta, “Metal Ion Removal from Aqueous Solution Using Physic Seed Hull,” Journal of Hazardous Materials, Vol. 179, 2010, pp. 363-372. doi:10.1016/j.jhazmat.2010.03.014
[8]	C. Gurses, M. Dogan and M. Yalcin, “Adsorption Kinetics of the Cationic Dye Methylene Blue onto Clay,” Journal of Hazardous Materials, Vol. 131, No. 1-3, 2006, pp. 217-228.doi:10.1016/j.jhazmat.2005.09.036
[9]	E. V. Mellis, M. C. P. Cruz and J. C. Casagrande, “Nickel Adsorption by Soils in Relation to pH, Organic Matter and Iron Oxide,” Scientia Agricola, Vol. 61, No. 2, 2004, pp. 190-195. doi:10.1590/S0103-90162004000200011
[10]	T. K. Sen and M. V. Sarzali, “Removal of Cadmium Metal Ion (Cd2+) from its Aqueous Solution by Aluminium Oxide: A Kinetic and Equilibrium Study,” Chemical Engineering Journal, Vol. 142, 2008, pp. 256-262. doi:10.1016/j.cej.2007.12.001
[11]	W. Weber and J. Morris, “Kinetics of Adsorption on Carbon from Solution,” American Society of Civil Engineers, Vol. 89, 1963, pp. 31-60.