BIOSORPTION OF Pb2+, Cd2+, & Ni2+ FROM WATERS BY ...

where ce is the equilibirium concentration (mg/L), qe the amount of Pb 2+ , Cd 2+ , and
Ni 2+ ions biosorbed (mg/g), cm is qe for a complete monolayer sorption capacity
(mg/g), Ka is a sorption equilibrium constant (L/mg). The values of cm and Ka were
determined from the intercept and the slope of 1/qe versus 1/ce; the linearized form of
Langmuir equation 2.2.
Freundlich isotherm model is based on the assumption of heterogeneous
surfaces as well as multilayer sorption and also being the binding sites are not
equivalent. It is expressed by the equation (Şeker, et al. 2008):
q e = K f c e n
The above equation can be rearranged to the following linear form:
log q e = log K f + n log c e
q e = c m exp(-kɛ 2 )
ɛ = RT Ln (1 + 1/ce) The equation (5) can be rearranged to the following linear form:
Ln q e = Ln c m - kɛ 2
(2.3)
(2.4)
where Kf and n are isotherm constants, respectively. The values of Kf and n are
calculated from the intercept and the slope of logqe versus logce; the linear form of
Freundlich equation 2.4.
Another isotherm model applied in this study is Dubinin-Radushkevich
isotherm model. The basic principles of this model is the Polany’s adsorption
potential theory and Dubinin’s minipore filling theory. Dubinin-Radushkevich
isotherm model can be given by the equation (Shahwan, et al. 2005):
where
(2.5)
(2.6)
(2.7)
where cm and k are the constants of Dubinin-Radushkevich isotherm
model,respectively, the maximum adsorption capacity (mol/g) and the adsorption
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