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<b>Kinetics and thermodynamics of aqueous Cu(II) adsorption on heat regenerated spent bleaching earth</b>

Enos W. Wambu
Gerald K. Muthakia
Joseph K. wa-Thiong’o
Paul M. Shiundu


This study investigated the kinetics and thermodynamics of copper(II) removal from aqueous solutions using spent bleaching earth (SBE). The spent bleaching earth, a waste material from edible oil processing industries, was reactivated by heat treatment at 370 oC after residual oil extraction in excess methyl-ethyl ketone. Copper adsorption tests were carried out at room temperature (22±3 oC) using 5.4 x 10-3 M metal concentrations. More than 70% metal removal was recorded in the first four hours although adsorption continued to rise to within 90% at 42 hours. The pH, adsorbent dosage and initial concentrations were master variables affecting RSBE adsorption of Cu(II) ions. The adsorption equilibrium was adequately described by the Dubinin-Radushkevich (D-R) and the Temkin isotherms and the maximum sorption capacity derived from the D-R isotherm was compared with those of some other low cost adsorbents. The adsorption process was found to follow Lagergren Pseudo-second order kinetics complimented by intra-particle diffusion kinetics at prolonged periods of equilibration. Based on the D-R isotherm adsorption energy and the thermodynamic adsorption free energy ∆G, it was suggested that the process is spontaneous and based on electrostatic interactions between the metal ions and exposed active sites in the adsorbent surface.

 KEY WORDS: Kinetics, Thermodynamics, Copper adsorption isotherms, Spent bleaching earth


Bull. Chem. Soc. Ethiop. 2011, 25(2), 181-190.

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eISSN: 1726-801X
print ISSN: 1011-3924