TITLE:
Application of Algerian Bentonite in the Removal of Cadmium (II) and Chromium (VI) from Aqueous Solutions
AUTHORS:
Mahfoud Barkat, Salah Chegrouche, Abdelhamid Mellah, Belgacem Bensmain, Djamel Nibou, Makhlouf Boufatit
KEYWORDS:
Adsorption, Cadmium, Chromium, Langmuir, Bentonite
JOURNAL NAME:
Journal of Surface Engineered Materials and Advanced Technology,
Vol.4 No.4,
July
17,
2014
ABSTRACT: The
aim of this study is to report batch adsorption results of Cd (II) and Cr (VI)
onto Algerian bentonite. The equilibrium adsorption process was achieved at
about 120 min contact time. The kinetic and isotherms aspects of Cr (VI) and Cd
(II) adsorption were investigated by varying operation parameters such as pH
(0.5 - 6), initial Cd (II) and Cr (VI) concentrations (50 - 200 mg/l) and
temperature (293.15 K - 343.15 K). The optimum conditions obtained were: pH =
6.0 and 4.0 for Cd (II) and Cr (VI) respectively, initial concentrations of Cd (II)
and Cr (VI) = 50 mg/L and T = 293.15 K. The kinetic of the adsorption process
was studied by application of the most important kinetic models namely the
pseudo-first order, the pseudo-second order and Elovich equations. The results
showed that the pseudo-second order model fitted well the adsorption data of Cr
(VI) whereas, and the Cd (II) adsorption data fitted best the Elovich equation.
The equilibrium data fitted best the Langmuir isotherm, and the maximum
adsorption capacity was determined through this model and was found to be 13.17
and 12.61 mg/g for Cd (II) and Cr (VI) respectively. The temperature had a
reverse effect on the Cd (II) and Cr (VI) adsorption; our results showed that
the removal efficiency increased to82.4% and 55.70% for Cd (II) and Cr (VI)when the temperature
decreasedto 293.15 K.The negative figures
of the Gibbs free energy ΔG°ads values range from －15.23 kJ/mol to －14.37 kJ/mol for Cd (II) and from －9.70 kJ/mol to －9.64 kJ/mol for
Cr(VI) at 293.15 K to 343.15 K showed that the adsorption process is
spontaneous and favourable. These results confirmed the ability of the low-cost
Algerian natural bentonite to efficiently and competitively adsorb the two
toxic elements investigated: cadmium (II) and chromium (VI).