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Removal of chromium ion
from leather industrial wastes by activated pure rice hulls
Mahejabeen Mukhtar
Department
of Chemistry, University of Karachi, Pakistan. E-mail:
prime1@super.net.pk.
Nomenclature:
C = concentration of adsorbate ions at equilibrium,
∆Go = Gibbs free energy of
adsorption (KJ/mol), ∆Ho =
enthalpy of adsorption (KJ/mol), K and n = Freundlich
isotherm coefficient, K = equilibrium constant
(L/mol), m = the amount of adsorbent (g), ∆S°
= entropy of adsorption (KJ/mol), X = the amount of
adsorbate ions (mg), and Xm = the adsorption maxima
(mol/g).
Accepted
10 September, 2007 |
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The removal of Cr ions from industrial wastage by adsorption
on rice hulls was investigated based on activated pure rice
hulls dosage, stay time, metal concentration and solution
temperature. The optimum values of activated pure rice hulls
dosage and stay time were determined to be 0.5 gm/50 ml
solution and 60 min, respectively, for the adsorption of Cr
ions. The constant for the Freundlich, D-R and Langmuir
isotherms were calculated at (293 – 323 K). The adsorption
of Cr from industrial wastage was found to be exothermic.
Thermodynamic parameters such as free energy (∆G°),
enthalpy (∆H°) and entropy (∆S°)
of adsorption was also calculated and interpreted from the
slope and intercept of the plots of In KD vs I/T.
The ∆G°
value decreases with rise in temperature and the negative
values of ∆H°
indicate that the adsorption of Cr from industrial wastage
was an exothermic process while positive values of change in
entropy (∆S°)
were also observed.
Key
words:
Adsorption, Cr metal, activated pure rice hulls. |
