Biomedical Engineering Reference
In-Depth Information
dQ
dt
)
2
(8)
t
=−
1
kQ Q
(
e
t
where
k
2
is the equilibrium rate constant of the pseudo-second-order kinetic model (g/
mg h). Integration of equation (8) between the boundary conditions of equation (6)
yields the following equation:
2
tQ kQ tQ
t
/
=
1
/ () /
+
(9)
2
e
e
The value of
k
2
can be determined by plotting
t
/
Q
t
versus
t
to obtain a straight line of
slope 1/
Q
e
and intercept of 1/(
k
2
Q
e
2
).
Since, the above two models cannot give definite mechanisms for the adsorption
process, another simplified model that represents the intra-particle diffusion model is
tested (Wu et al., 2001).
This model, which is based on the theory proposed by Weber
and Morris assumes that the intra-particle mass transfer resistance is the rate determin-
ing step which means that the adsorption process is pore diffusion controlled (Weber
and Morris, 1962). According to this theory, the initial rates of intra-particle diffusion
can be obtained from the following equation:
=+
12
/
Qxkt
t
(10)
i
p
where
x
i
is a constant proportional to the boundary layer thickness, mg/g,
k
p
is the in-
traparticle diffusion rate constant (mg/(g h
1/2
)) (Kavitha and Namasivayam, 2007). For
pore diffusion controlled sorption, a plot of
Q
t
versus
t
1/2
gives a straight line of slope
k
p
and an intercept of
x
i
.
CoNClusioN
Chitosan, a biopolymer, has attracted considerable attention due to its many physi-
cal and chemical properties and due to its many applications including its usage as
a material for medical applications, such as artificial skin and immunosuppressant.
In addition, resins derived from chitosan have been synthesized and characterized.
The chelation and sorption properties of these chitosan-based polymers towards heavy
metal ions in aqueous solutions have been investigated by several research groups.
Therefore, the aim of this article will be to shed some light on some of these chitosan-
derived resins and their application to sorption of heavy metal ions and some anions.
KeyWords
•
Biodegradable
•
intraparticle diffusion
•
magnetic field
•
Polychlorinated biphenyl
•
thermodynamic
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