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Bulletin of the Chemical Society of Ethiopia

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

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

Abstract


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.




http://dx.doi.org/10.4314/bcse.v25i2.65857
AJOL African Journals Online