JOURNAL OF
ENVIRONMENTAL
SCIENCES
ISSN 1001-0742
CN 11-2629/X
www.jesc.ac.cn
Available online at www.sciencedirect.com
Journal of Environmental Sciences 2012, 24(8) 1425–1432
Adsorptive removal of iron and manganese ions from aqueous solutions with
microporous chitosan/polyethylene glycol blend membrane
Neama A. Reiad
1,∗
, Omar E. Abdel Salam
2
, Ehab F. Abadir
2
, Farid A. Harraz
3
1. Sanitary & Environmental Department, Housing & Building National Research Center, 87 el Tahrir st., Dokki, Egypt
2. Department of Chemical Engineering, Faculty of Engineering, Cairo University, Giza, Egypt
3. Advanced Materials Technology Department, Central Metallurgical R & D Institute, Helwan, Egypt
Received 13 October 2011; revised 28 December 2011; accepted 31 December 2011
Abstract
Microporous chitosan (CS) membranes were directly prepared by extraction of poly(ethylene glycol) (PEG) from CS/PEG blend
membrane and were examined for iron and manganese ions removal from aqueous solutions. The different variables affecting the
adsorption capacity of the membranes such as contact time, pH of the sorption medium, and initial metal ion concentration in the
feed solution were investigated on a batch adsorption basis. The affinity of CS/PEG blend membrane to adsorb Fe(II) ions is higher
than that of Mn(II) ions, with adsorption equilibrium achieved after 60 min for Fe(II) and Mn(II) ions. By increasing CS/PEG ratio in
the blend membrane the adsorption capacity of metal ions increased. Among all parameters, pH has the most significant effect on the
adsorption capacity, particularly in the range of 2.9–5.9. The increase in CS/PEG ratio was found to enhance the adsorption capacity
of the membranes. The effects of initial concentration of metal ions on the extent of metal ions removal were investigated in detail.

–NH
2
, –SO
3
H, and –COOH that can interact with heavy
metal ions (Liu and Bai, 2006).
Chitosan is a natural biopolymer with a high content
of –NH
2
and –OH functional groups and is inexpen-
sive, abundant, biodegradable, and widely available from
sea food-processing wastes (Guibal, 2004; Ravi-Kumar,
2000). The high adsorption potential of chitosan for heavy
metals can be attributed to (1) high hydrophilicity due
to large number of hydroxyl groups of glucose units, (2)
presence of large functional groups, (3) high chemical
reactivity of these functional groups, and (4) flexible struc-
ture of the polymer chain (Grini, 2005). Polymer blending
technology is an effective way to obtain new polymeric
materials with optimized properties. The advantages of
this technology include versatility, simplicity and inexpen-
siveness (Li et al., 2007; Rodrigues et al., 2008). New
tubular alumina/chitosan composite membrane is synthe-
sized, where a porous alumina support was manufactured
with a centrifugal casting technique. The porosity of the
coating was controlled with a phase inversion method
using silica as a porogen, and the capacity of adsorption
was about 0.2 g Cu
2+
/g chitosan (Steenkamp et al., 2002).

Chitosan (CS) powder (high molecular weight, > 75%
deacetylated) was purchased from Sigma Aldrich. Acetic
acid (glacial, 99%–100%), Poly (ethylene glycol) (PEG
6000), and glutaraldehyde were obtained from Mer-
ck (Mumbai, India). Mineral salts, manganese chloride
(MnCl
2
·4H
2
O), and ferric chloride (FeCl
3
·6H
2
O) were
obtained from SD fine Chemistry Ltd. (Mumbai, India).
The water used for experiments was obtained by double
distillation of de-ionized water.
1.2 Preparation of chitosan-PEG blend (CSB) mem-
branes
Chitosan dissolved in 2% acetic acid (75 mL) and the coun-
terpart polymer (PEG 6000) dissolved in water (25 mL)
with different mass ratios (CS/PEG: 1:1, 2:1 and 4:1) were
mixed thoroughly and stirred for 1 hr. To this solution, 1
mL of 2% glutaraldehyde solution (cross-linking agent)
was added under stirring at room temperature (27°C).
The solution was transferred immediately into a Teflon
covered glass plate (100 mm × 100 mm × 3 mm) and
dried at 80°C in an electric oven (TK 3108, EHRET,
Germany) for 4 hr. The formed cross-linked chitosan-
PEG blend membranes were neutralized with 2% aqueous

1.4 Characterization of chitosan-PEG blend mem-
branes
The structures and morphologies of the blend membranes
were examined through scanning electron microscopy
(Inspect S, FEI Ltd., Holland) after gold coating. The
fractured cross-sections of the membranes were achieved
by breaking the samples deeply cooled in liquid nitrogen.
The crystallinity of the blend membranes was measured
by X-ray diffraction (X Pert Bro, Panalytical, Holland).
XRD measurements were carried out at room temperature,
using Nickel-filtered Cu Kα radiation generated at 45 kV,
CS:PEG 1:1 CS:PEG 2:1 CS:PEG 4:1
Fig. 1 Photos of CSB membranes with different compositions of CS:PEG.
No. 8 Adsorptive removal of iron and manganese ions from aqueous solutions with microporous chitosan/polyethylene glycol blend membrane 1427
and 50 mA. The diffraction patterns were determined over
adiffraction angle range of 2θ = 5–80
◦
.
Thermal studies of the blend membranes were measured
using a differential scanning calorimeter (DSC-H50, Shi-
madzu, Japan). Heating and cooling rates were 10°C/min.
All experiments were done with dry N
2
at flow rate 10
mL/min from room temperature to 400°C.
1.5 Adsorption and desorption experiments
The membranes were cut into pieces at about 1 cm length
then dried in a vacuum oven at 80°C for 2 hr. Then it
was removed quickly and stored in desiccators over a fresh
silica gel at ambient temperature. The adsorption and des-

(C
0
− C)
C
× 100% (3)
where, C
0
(mg/L) and C (mg/L) are the concentrations of
the metal ions in the sorption medium before and after
equilibrium, respectively; V (mL) is the volume of the
sorption medium; and m (g) is the weight of the dry
membrane.
Adsorption kinetic studies were conducted for the CSB
membranes with CS:PEG ratio of 1:1 and 2:1. Certain
amounts of the dried CSB membrane pieces was added
into Fe(II) (pH 5) and Mn(II) (pH 5.9) ions solutions.
Initial Fe(II) and Mn(II) ions concentrations were 2 mg/L.
The samples were taken at desired time intervals for the
analysis of metal ion concentrations.
The mixture of Fe(II) and Mn(II) ions solution and CSB
membranes was agitated during the period of 0–90 min
to determine the time required to reach equilibrium at
ambient temperature. The adsorption capacity is referring
to the maximum amount of metal ions removed from
the solution when the ionic sites of the membranes are
saturated.
pH dependent metal adsorption was performed by agi-
tating the mixture of CSB membrane samples, Fe(II) and
Mn(II) solutions, separately for 1 hr and varying pH in the
range 2–9.

is in agreements with the results obtained by Zeng and
Fang (2004) for preparation of sub-micrometer porous
membrane from chitosan/polyethylene glycol semi-IPN.
Differential scanning calorimeter (DSC) analysis was
carried out to determine the thermal properties of the
membranes. Special care must be taken during DSC mea-
surements since chitosan and the counterpart polymer are
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 90 120 180 240 300 360 400
Swelling rate (g/g)
Time (min)
CS:PEG 1:1
CS:PEG 2:1
CS:PEG 4:1
Fig. 2 Swelling rate of CSB membranes prepared at different composi-
tion of CS:PEG.
1428 Journal of Environmental Sciences 2012, 24(8) 1425–1432 / Neama A. Reiad et al. Vol. 24
a
b
c
d
e
f

0
2
4
6
8
10
12
23.0 24.6 47.1 217.4 285.5 344.5 394.0
Heat flow endo up
Temperature (°C)
CS
CS:PEG 1:1
CS:PEG 2:1
Fig. 4 DSC curves of CS, CS:PEG blend 1:1 and CS:PEG blend 2:1.
state.
The XRD patterns of CS powder and CSB membranes
are shown in Fig. 5. Crystalline peaks for CS appears at 2θ
= 20.1
◦
, 12.5
◦
, and 8.9
◦
. While for CSB membranes with
CS:PEG ratio 1:1, its reflection pattern at 2θ = 12.5
◦
, 8.9
◦
are almost the same as those of CS but its reflection pattern
at 2θ = 20.1

kinetics can be seen within the first 20 min, while equilib-
rium was attained after 60 min for Fe(II) and Mn(II). The
maximum values of metal adsorption capacities in CSB
membranes were found to be 38 and 18 mg/g membrane
for Fe(II) and Mn(II), respectively.
Kinetics in a chelating polymer are not only relying on
the availability of chelating functional groups, but also
on their accessibility by counter ions without a steric
hindrance, which is greatly determined by the polymeric
matrices characteristics (Kantipuly et al., 1990). The rapid
metal adsorption kinetics in the CSB membranes can be
attributed to the strongly acidic and hydrophilic nature
of the membrane caused by the presence of amine and
hydroxyl groups which are responsible of interaction with
the metal ions by electrostatic attraction. However, time
required to attain equilibrium in this study for the adsorp-
tion of Fe(II), and Mn(II) ions in CSB membranes seems
to be suitable from kinetic considerations when compared
with the results stated in the literature (Denizli et al., 1998)
where time required to attain equilibrium ranged from 30
min to 7 hr.
The pH of a solution is an important parameter in
the adsorption process because of the pH dictates not
only the dissociation of functional groups but also the
complexation reactions or electrostatic interactions at the
adsorption surface (Elliot and Huang, 1981). Since CSB
membrane is anionic sorbent with its molecular structure
having pendant amine and hydroxyl functional groups,
the effect of pH on the adsorption capacities of heavy
metal ions was examined in the pH range 2–9. As shown

20
25
30
35
40
45
10 20 40 60 80
Time (min)
CS:PEG 1:1
CS:PEG 2:1
0
2
4
6
8
10
12
14
16
18
10 20 40 60 80
Mn (mg/g membrane)
Fe (mg/g membrane)
Time (min)
Fe(II) Mn(II)
Fig. 6 Effect of contact time on Fe(II) and Mn(II) removal using CSB membranes with different CS:PEG ratios. Adsorption conditions: initial
concentration 2.0 mg/L; sorption medium volume 250 mL; agitation rate 300 r/min; temperature 27°C, pH 5.
0
5
10

0
10
20
30
40
50
60
70
80
90
0.5 1 3 5 7 10
Q
e
(mg metal/g membrane)
Initial metal concentration (mg/L)
0
5
10
15
20
25
30
35
40
0.5 1 3 5 7 10
Q
e
(mg metal/g membrane)
Initial metal concentration (mg/L)
CS:PEG 1:1

of metal ions even after four cycles as listed in Table 1.
This clearly shows that, CSB membranes can be effectively
and economically used for the removal of heavy metal ions
from aqueous solutions.
Table 1 Reusability of CSB membranes for removal of Fe(II) and
Mn(II)
Cycle Amount of adsorbed metal ions (mg/g)
Fe(II) Mn(II)
1 80.0 35.0
2 78.8 35.0
3 76.1 34.5
4 76.0 34.4
Adsorption conditions: initial concentration of metal ions 5 mg/L; vol-
ume of adsorption medium 250 mL; agitation rate 300 r/min; pH 5.9;
temperature 27°C; adsorption time 60 min.
Desorption conditions: desorption medium 0.1 mol/L HCl; volume of
desorption medium 250 mL; desorption time 6 hr, temperature 27°C.
2.5 Adsorption isotherm
An adsorption isotherm equation is an expression of the
relation between the amount of solute adsorbed and the
concentration of the solute in the fluid phase. As the
adsorption isotherms are important to describe how adsor-
bates interact with the adsorbents and so are critical for
design purposes; therefore, the correlation of equilibrium
data using an equation is essential for practical adsorption
operation (Deomall et al., 2003). Freundlich and Langmuir
sorption isotherm equations were adopted in this study.
Freundlich sorption isotherm, one of the most widely
used mathematical descriptions, gives an expression en-
compassing the surface heterogeneity and the exponential

=
(bq
m
C
e
)
(1 + bC
e
)
(5)
where, q
m
and b are Langmuir constants related to the
sorption capacity, and sorption energy, respectively. The
plots of C
e
/q
e
against C
e
are shown in Fig. 9c and d.
The constants and correlation coefficients (R
2
) of Fre-
undlich and Langmuir isotherm are listed in Table 2.
As can be observed, experimental data were better fitted
to Freundlich equation than to Langmuir equation, and
therefore it is more suitable for the analysis of kinetics.
No. 8 Adsorptive removal of iron and manganese ions from aqueous solutions with microporous chitosan/polyethylene glycol blend membrane 1431
y = 0.064x

0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.5 1 3 5 7 10
C
e
/q
e
(g/L)
C
e
(mg/L)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.30
0.40
0.5 1 3 5 7 10
C
e
/q

0.001
R² = 0.921
log(C
e
/q
e
)
logC
e
a
c
d
bFe(II)
Fe(II)
Mn(II)
Mn(II)
Fig. 9 Freundlich plot of CSB membranes (a, b); and Langmuir plot of CSB membranes (c, d) for Fe(II) and Mn(II) removal.
Table 2 Freundlich and Langmuir parameters for the sorption of Fe(II) and Mn(II) onto CSB membranes
Adsorbent Freundlich Langmuir
knR
2
bq
m
R
2
Fe(II) CS:PEG 1:1 0.050 15.6 0.832 0.359 71.4 0.787
CS:PEG 2:1 0.040 16.4 0.703 0.333 90.9 0.682
Mn(II) CS:PEG 1:1 0.053 7.5 0.994 –6.760 18.5 0.923
CS:PEG 2:1 0.050 7.9 0.990 –46.100 21.7 0.921
3 Conclusions

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