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Title: Equilibrium, kinetic and thermodynamic modeling for the adsorption of heavy metals onto chemically modified hydrotalcite
Authors: Anirudhan, T S
Suchithra, P S
Keywords: Hydrotalcite;Heavy metals;Adsorption;Isotherms;Kinetics;Thermodynamics
Issue Date: Jul-2010
Publisher: CSIR
Abstract: The adsorption of heavy metals (Cu(II), Zn(II) and Cd(II)) from aqueous solutions with tannin-immobilized calcined hydrotalcite (TA-HTC) was studied using batch experiment technique. The surface characterizations of the adsorbent were investigated. Kinetic modeling of removal of metals was done using a pseudo-second-order rate expression. The intraparticle mass transfer diffussion of metals on adsorbent represented the rate-limiting step, with the activation energy of 27.05, 24.22 and 21.96 kJ/mol for Cu(II), Zn(II) and Cd(II), respectively. Experimental results showed that the adsorption of metals was selective to be in the order of Cu(II)>Zn(II)>Cd(II). Equilibrium isotherm data for metal ions were analyzed by the Langmuir, Freundlich, Dubinin-Radushkevich and Scatchard equations. The Langmuir adsorption isotherm described the adsorption data very well at all studied temperatures. Thermodynamic parameters such as standard enthalpy (ΔH), standard entropy (ΔS), standard free energy (ΔG), activation energy and isosteric enthalpy and entropy were calculated and the results are discussed in detail.
Page(s): 247-259
ISSN: 0975-0991 (Online); 0971-457X (Print)
Appears in Collections:IJCT Vol.17(4) [July 2010]

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