Removal of Ni(II) and Zn(II) from Aqueous Media …
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Table 1 Models and their parameters
Models (adsorption and kinetic) Governing equations
Parameters
Langmuir model
q e =
qmax K b Ce
1+K b Ce
q e (mg/g): An amount of ions
adsorbed at equilibrium per unit
mass of adsorbent.
q max (mg/g): Maximum
adsorption capacity
K b (1/mg): Langmuir
adsorption constant
Freundlich model
q t = K F C
1
n
e
K F : Freundlich adsorption
constant
n: The empirical parameter
indicating adsorption
favorability
Harkins-Jura model
1
q 2
e
=
B
A −
1
A log C e
A, B: Harkins Jura adsorption
constants
Pseudo-First order
q t = q e
1 − exp(−K 1 t)
q t (mg/g): Adsorption capacity
at time t
q e (mg/g): Adsorption capacity
at equilibrium
K 1 (1/min): Rate constant of
Pseudo first order adsorption
t(min): Time of contact
Pseudo-Second order
q t =
q 2
e K2t
1+t K2qe
q t (mg/g): Adsorption capacity
at time t
K 2 (g/mg min): Rate constant of
Pseudo Second order adsorption
Intra-Particle diffusion model
q t = K id t 2 + I
q t (mg/g): Adsorption capacity
at time t
K id
mg/g min 2
: Intra particle
diffusion rate constant
I : Intercept representing
boundary layer thickness
Table 2 Isotherm parameters for Zn(II) and Ni(II) adsorption onto the ABC
Models
Parameters
Metal ions Zn(II) Ni(II)
Langmuir
q max
mg
g
125
142.85
K b
L
g
0.25
0.028
R 2
0.9633
0.9707
Freundlich
K F
7.4
9.7
n
1.82
1.859
R 2
0.9234
0.95
Harkins-Jura
A
714
970.87
B
1.992
1.893
R 2
0.701
0.723