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

  • Enos W. Wambu Department of Chemistry, Kenyatta University, P.O. Box 43844-00100, Nairobi, Kenya
  • Gerald K. Muthakia Department of Chemistry, Kimathi University College of Technology, P.O. Box 657-10100, Nyeri, Kenya
  • Joseph K. wa-Thiong’o Department of Chemistry, Kenyatta University, P.O. Box 43844-00100, Nairobi, Kenya
  • Paul M. Shiundu Department of Chemistry, University of Nairobi, P.O. Box 30197-00100, Nairobi, Kenya
Keywords: Kinetics, Thermodynamics, Copper adsorption isotherms, Spent bleaching earth

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.

Published
2011-04-29
Section
Articles

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