Regular Article
The Influence of Temperature on the Adsorption of Cadmium(II) and Cobalt(II) on Kaolinite

https://doi.org/10.1006/jcis.1998.5549Get rights and content

Abstract

The adsorption of Cd(II) and Co(II) onto kaolinite was investigated at five temperatures between 10 and 70°C. Adsorption edges showed that both Cd(II) and Co(II) adsorbed onto kaolinite in two stages, separated by a plateau between pH 4 and 7. Initial adsorption commenced at about the same pH for both cations, but at each temperature the second-stage adsorption occurred at a slightly lower pH for Co(II) than for Cd(II). At higher temperatures adsorption was generally shifted to lower pH. Adsorption isotherms at pH 5.50 for both cations could be fitted closely by a simple Langmuir model at all temperatures. A two-site Langmuir model provided a substantially better fit for isotherms at pH 7.50 for Cd(II) and pH 7.00 for Co(II). At pH 5.50 the maximum adsorption density estimated from Langmuir modelling was approximately the same (1 μmol m−2) for both cations and at all temperatures. A similar value was found for one of the model sites at pH 7.50 for Cd(II) and at pH 7.00 for Co(II). Potentiometric titrations of kaolinite suspensions, in the presence and absence of added Cd(II) or Co(II), could be modeled accurately by a constant-capacitance surface complexation model. The data for adsorption of both cations could be fitted at all temperatures using a model that assumed ion exchange at permanent charge sites on silanol faces and complexation to hydroxyl edge groups. Thermodynamic parameters estimated from both the Langmuir and surface complexation models showed that adsorption of Cd(II) and Co(II) were endothermic. For the surface complexation model, enthalpies of adsorption on exchange sites were about 10 kJ mol−1, but at the variable-charge sites the enthalpy changes were about 70 kJ mol−1. For all these reactions the entropy changes were positive, with values of the order of 100 J K−1mol−1. Trends for the Langmuir model were qualitatively similar.

References (33)

  • R.O. James et al.

    J. Colloid Interface Sci.

    (1972)
  • M.M. Benjamin et al.

    J. Colloid Interface Sci.

    (1981)
  • M.M. Benjamin et al.

    J. Colloid Interface Sci.

    (1981)
  • G Micera et al.

    Colloids Surfaces

    (1987)
  • B. Nowack et al.

    J. Colloid Interface Sci.

    (1996)
  • M.A. Ali et al.

    Geochim. Cosmochim. Acta

    (1996)
  • P.V. Brady et al.

    J. Colloid Interface Sci.

    (1996)
  • D.P. Rodda et al.

    J. Colloid Interface Sci.

    (1996)
  • L.G.J. Fokkink et al.

    J. Colloid Interface Sci.

    (1990)
  • M.J. Angove et al.

    Colloids Surfaces A

    (1997)
  • P.W. Tewari et al.

    J. Colloid Interface Sci.

    (1975)
  • H. Tamura et al.

    J. Colloid Interface Sci.

    (1983)
  • M.A. Malati et al.

    Surf. Technol.

    (1982)
  • P.V. Brady

    Geochim. Cosmochim. Acta

    (1992)
  • P.V. Brady

    Geochim. Cosmochim. Acta

    (1994)
  • P.W. Schindler et al.

    Netherlands J. Agric. Sci.

    (1987)
  • Cited by (157)

    • Removal of heavy metals from aqueous solutions by adsorption using single and mixed pillared clays

      2019, Applied Clay Science
      Citation Excerpt :

      Those two models are the most used to adjust the adsorption of copper, cobalt and cadmium. Angove et al. (1998) studied the influence of temperature (283 to 343 K) on adsorption of Co(II) on kaolinite and found that the experimental data fit the Langmuir model at all temperatures. The use of raw kaolin for removing Co(II) from aqueous solution (Yavuz et al., 2003) has yielded Langmuir monolayer capacities of 1.5 mg g−1at 313 K. Different adsorbents have been used for removal of Cd(II) from aqueous solutions and the results closely follow the Langmuir model of adsorption (Alvarez-Ayuso and Garcia-Sanchez, 2003) or Freundlich equation (Jobstmann and Singh, 2001).

    View all citing articles on Scopus
    1

    To whom correspondence should be addressed.

    View full text