Synthesis and characterization of nanocomposite NiFe2O4@SalenSi and its application in efficient removal of ni(II) from aqueous solution

Article abstract of DOI:10.4314/bcse.v32i1.7

In this work, nano ferrite spinel NiFe2O4 was synthesized by sol-gel method and characterized by SEM, XRD, FT-IR, and VSM. In second step Schiff base made from salicylaldehyde and amino propyl triethoxy silane was used for modification of the synthesized

Full text of DOI:10.4314/bcse.v32i1.7

Bull. Chem. Soc. Ethiop. 2018, 32(1), 77-88.
2018 Chemical Society of Ethiopia and The Authors
DOI: https://dx.doi.org/10.4314/bcse.v32i1.7
ISSN 1011-3924
Printed in Ethiopia

2 4
SYNTHESIS AND CHARACTERIZATION OF NANOCOMPOSITE NiFe O @SalenSi
AND ITS APPLICATION IN EFFICIENT REMOVAL OF Ni(II)
FROM AQUEOUS SOLUTION
1
1*
2
Narjes Babadi , Haman Tavakkoli and Mozhgan Afshari
1
Department of Chemistry, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran
Department of Chemistry, Shushtar Branch, Islamic Azad University, Shushtar, Iran
2
(Received June 15, 2017; Revised January 6, 2018; Accepted January 8, 2018)
2 4
ABSTRACT. In this work, nano ferrite spinel NiFe O was synthesized by sol-gel method and characterized by
SEM, XRD, FT-IR, and VSM. In second step Schiff base made from salicylaldehyde and amino propyl triethoxy
silane was used for modification of the synthesized nano ferrit. In the third step removal of Ni(II) was done using
modified adsorbent and 95% efficiency was achieved. The removal rate was determined by atomic absorption
spectroscopy. These studies showed that the Freundlich isotherm model was fitted well with adsorption data.
Moreover, the pseudo-second order kinetic model was fitted very well with experimental data. The results
2 4
demonstrated that NiFe O @SalenSi nanoadsorbent can be used for the removal and recovery of metal ions from
wastewater over a number of cycles, indicating its suitability for the design of a continuous process.
KEY WORDS: Nano ferrite, Sol-gel method, Schiff base, Removal of Ni(II), Magnetic nanocomposite
INTRODUCTION
The scarcity of water in terms of both quantity and quality has become a significant threat to the
well-being of humanity. In particular, the quality of drinking water has become a serious
concern, with the rapid escalation of industrialization towards a developed society. The waste
products generated from the textiles, chemicals, mining and metallurgical industries are mainly
responsible for contaminating the water [1]. This contaminated water contains non-
biodegradable effluents, such as heavy metal ions (arsenic, zinc, copper, nickel, mercury,
cadmium, lead and chromium, etc.) and organic materials that are carcinogenic to human beings
and harmful to the environment [2]. According to the WHO, the limit of the toxicity value for
nickel is 130 μg/L, assuming a 60 kg adult, drinking two liters of water per day. However, the
presence of nickel at higher levels in the human body can cause serious lung and kidney
problems as well as gastrointestinal distress, pulmonary fibrosis and skin dermatitis [3].
Several conventional methodologies such as precipitation [4], ion exchange [5], filtration
membrane technology [6], electrochemical processes [7] and adsorption process [8] are
available for heavy metal removal and other pollutants from wastewaters. Generally, they are
expensive or ineffective sometimes, especially when the metal concentration is higher than 100
mg/L [9]. Among all the treatments proposed, adsorption using sorbents is one of the most
popular methods. It is now recognized as an effective, efficient and economic method for water
decontamination applications and for separation for pilot purpose.
Some nanoadsorbents can be easily recovered or manipulated with an external magnetic
field and show a good capacity for the rapid and efficient adsorption of multivalent metal
cations from aqueous solutions. Composite microspheres can be applied to remove heavy metal
ions from industrial wastewater because the surface of the microspheres is covered with SiO ,
2
2
+
2+
2
and the SiO is inactive and can adsorb heavy metal ions (such as Hg and Pb ) [10], or using
supplementary material modification process magnetic nano particles, for example: capped by
thiol [11], capped by amine [12] or capped by Schiff base [13]. The use of monodisperse amine-
_
*
_________
Corresponding author. E-mail: h.tavakkoli@iauahvaz.ac.ir, htavakkoli59@gmail.com
This work is licensed under the Creative Commons Attribution 4.0 International License

78
Narjes Babadi et al.
terminated Fe
3
O
4
@SiO
2
–NH
2
for the removal of metal ions was recently reported. These amine-
2
+
terminated core-shell magnetic nanoparticles show effective removal of Pb [14] and removal
heavy metals hybrid composite such as: Fe –SiO -poly(1,2-diaminobenzene) [15], amine-
Fe O @SiO @meso-SiO [16] and EDTA-γ-Fe O @SiO /Thiol-γ-Fe O @SiO [17]. The
3
O
4
2
3
4
2
2
3
4
2
3
4
2
effective removal of heavy metal ions from an aqueous solution using modified magnetic
nanoparticles by polymer [18] for example polypyrrole [19] has been developed by the covalent
binding of poly(acrylic acid) on the surface of Fe O nanoparticles followed by sulfonation
3 4
using sulfanilic acid via carbodiimide activation [20] capped by EDA polymers [21]. Amine-
functionalized magnetite chitosan nanocomposites as a recyclable tool was used for the removal
of heavy metals (amine-Fe
acids such as humic acid (humic acid-Fe
Also to remove heavy metals by magnetic nanoparticles surface modification using some
chemicals such as DMSA (DMSA-Fe ) [24]. There is recent research from composite to
remove heavy metal ions from aqueous solutions used. The optimum conditions for this research
3
O
4
@SiO
2
) [22], magnetic nanoparticles surface modification using
3
O
4
) [11] and ascorbic acid (ascorbic acid-Fe ) [23].
3 4
O
3
O
4
2
+
2+
2+
3+
2+
pH 6, 24 h as well as the reaction efficiency100% (Cu , Pb , Hg , As ), 40% (Co ), 22%
2
+
2+
(
Cd ) and 25% (Ni ) [25, 26].
In this work, nano ferrite spinel NiFe O was synthesized. In second step Schiff base made
2
4
from salicylaldehyde and amino propyl triethoxysilane was used for modification of synthesized
nano ferrit, also the characterization of such new phases and their capabilities toward Ni(II)
removal were done, respectively. Therefore, in the batch system the effects of pH, adsorbent
dosage, initial concentration and contact time on the adsorption capacity were investigated.
EXPERIMENTAL
Reagents
Ni(NO ) .6H O (99.99% purity) and Fe(NO ) .9H O (99.99% purity) were obtained from
3
2
2
3
3
2
Merck, Germany; citric acid (CA) (99.5% purity) was purchased from Aldrich, USA. NaOH
(
99.99% purity), HCl (37.00% purity), CH OH (99.99% purity), C H OH (99.99% purity),
3
2
5
salicylaldehyde (C
7
O
2
H
7
), 3-amino propyl triethoxysilane (C
6
H
6
O
3
2
NH Si) were provided by
Merck. All the reagents were of analytical grade and thus used as received. Also deionized
water was used throughout the experiments.
2 4
Preparation of NiFe O
The nickel ferrite was synthesized by sol-gel method. First the aqueous solution of metal nitrate
with nominal atomic ratios Fe:Ni = 2:1 was mixed together in deionized water. Citric acid (CA)
was proportionally added to the metal ion solution to gain the same amounts of equivalents. The
o
solution was concentrated by evaporation at approximately 50 C with simultaneous stirring for
1
h to convert it to stable (Fe, Ni)/CA complex. The solution was heated (while being stirred) at
o
approximately 75 C to remove excess water. Then the dry gel was obtained by letting the sol
into an oven heating it slowly up to 110 C and keeping it for 6 h in a baking oven. The gel
o
2 4
pieces were grounded in an agate mortar to form fine powder. Finally NiFe O nanoferrite was
obtained.
Preparation of the Schiff base
The Schiff base was synthesized according to the literature [27]. A solution of salicylaldehyde
4 mmol) in CH CN or CH OH (20 mL) was treated with amino propyl triethoxysilane in a
(
3
3
molar ratio of 1:1.5. The reaction mixture was refluxed for four hours. The result was a pale
yellow Schiff base that is shown in (Scheme 1).
Bull. Chem. Soc. Ethiop. 2018, 32(1)

Synthesis and characterization of nanocomposite NiFe
2
O
4
@SalenSi
79
Scheme 1. Preparation process of Schiff base bonding to nickel ferrite.
Preparation of nano composites NiFe O @SalenSi
2
4
At this stage nickel ferrite (1 mmol) was added to the solution. Then the reaction mixture was
refluxed for twenty-four hours. The solid residue was filtered and washed with CH OH (8
3
drops) and chloroform (3 drops). After that it was laid in the desiccators for a few hours in order
to be dried, shown in (Figure 1).
2 4
Figure 1. An illustration for NiFe O @SalenSi nanoadsorbents.
Adsorbent characterization
Several techniques were employed to analyze and validate the synthesized powder. For
o
structural investigation of calcinated powder at 700 C, powder X-ray diffraction (XRD)
o
measurements were carried out in the region of (2θ = 20 to 70 ) using CuK
α
radiation on a
Rigaku D/MAX RB XRD diffract meter equipped with a curved graphite monochromator. To
study the surface morphology scanning electron microscopy (SEM) images were carried out.
The complex polymeric gel and derived powders have been also analyzed by Fourier transform
infrared spectroscopy (FTIR) on Perkin Elmer BX II FTIR spectrometer. The magnetic
properties (M-H curve) were evaluated on a BHV-55 vibrating sample magnetometer (VSM).
This analysis was measured at room temperature using the magnetic field 1000 Oe to -1000 Oe.
Finally with the help of atomic absorption spectroscopy AAS final concentration of nickel ions
was achieved.
Ni(II) removal experiments
A prepared solution of Ni(II) was distributed into different flasks (1 L capacity) and pH was
adjusted with the help of the pH meter (HORIBA F 11 E, Japan made). The initial pH value of
the soluble metal ion was adjusted to the desired levels, using either HCl (0.5 M) or NaOH (0.5
2 4
M). A known mass of NiFe O @SalenSi powder (adsorbent dosage) was then added to 20 mL
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80
Narjes Babadi et al.
of soluble [Ni(II)], and the obtained suspension was immediately stirred for a predefined time.
All experiments were done at room temperature. The investigated ranges of the experimental
variables were as follows: concentrations of pollutants (10-50 mg/L), pH of solution (2-11),
adsorbent dosage (0.02, 0.03 and 0.04 g) and mixing time (30-120 min).
Adsorption capacity and removal efficiency were calculated according to the following
equations [28]:
C  C (e)
o
(1)
Removal rate % 
100
Co
where qe (mg/g) is adsorption capacity; E (%) is removal efficiency; C (mg/L), and C (mg/L)
0
e
are initial and equilibrated adsorbate concentrations, respectively;
Reusability of nanoadsorbents
2 4
To test the reusability of the nanoadsorbents, the NiFe O @SalenSi nanoadsorbents containing
Ni(II) were washed with CH OH. After that NiFe @SalenSi nanoadsorbents were thoroughly
3
2 4
O
o
washed with deionized water till. Then, the washed nanoadsorbents were at 150 C for 15 min
and reused for the subsequent adsorption cycle. Five cycles of consecutive adsorption–
desorption–regeneration were carried out to validate the reusability of NiFe
2 4
O @SalenSi
nanoadsorbents for the removal and recovery of Ni(II).
RESULTS AND DISCUSSION
X-Ray diffraction
o
XRD patterns of the synthesized powder which was calcinated at temperature 700 C for 9 h
o
(
heating rate: 3 C/min) is shown in (Figure 2). XRD results reveal the existence of nano ferrite
o
for sol-gel method. When the precursor was calcinated at 700 C for 9 hours, several sharp
peaks were observed attributed to the nano ferrite NiFe by comparison with standard XRD
spectra. The diffraction peaks at 2θ angels appeared in the order of 30.27 , 35.75 , 43.33 ,
2
O
4
o
o
o
o
o
o
4
3.56 , 57.4 and 62.9 can be assigned to scattering from the (2 2 0 ), (3 1 1), (4 0 0), (5 1 1)
and (4 4 0) planes of the nano ferrite NiFe O type crystal lattice, respectively. XRD data shows
2
4
2 4
NiFe O crystallizes in a hexagonal phase with (a = b = 4.866, c = 12.652) and space group
-
3
R m (166). The crystallite sizes were calculated using XRD peak broadening of the (311) peak
using the Scherer’s formula:
0
.9
(2)
Dhkl

hkl coshkl
where Dhkl is the particle size perpendicular to the normal line of (hkl) plane, βhkl is the full width
at half maximum, θhkl is the Bragg angle of (hkl) peak, and λ is the wavelength of X-ray. The
o
particle size of nanoparticles calcinated at 700 C is about 52.75 nm.
SEM analysis
Scanning electron microscopy (SEM) of nanoferrite prepared by the sol-gel method and
modified by Schiff base is shown in Figure 3 (a, b). (a): This image, exhibit typical morphology
for prepared nanopowders (NiFe O ) with uniform particles distribution and regular shapes. (b):
2 4
The micrograph represents formation of agglomerated particles with Schiff base addition.
However, appearance of bigger particles on the surface seems to be dominant.
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Synthesis and characterization of nanocomposite NiFe
2
O
4
@SalenSi
81
o
Figure 2. XRD patterns of samples of the NiFe O nanopowder calcinated at 700 C.
2
4
2 4
Figure 3. (a) SEM images of the NiFe O nanopowders and (b) SEM images of the
NiFe @SalenSi nanoadsorbents.
2
O
4
FT-IR spectroscopy
The FT-IR spectra of the NiFe O fresh xerogel and calcinated xerogel and NiFe O @SalenSi in
2
4
2
4
-
1
the range of 500-4000 cm are shown in Figure 4 (a, b, c). The dried gel of the sample shows
the characteristic peaks at about 1778.17, 1643.81 and 1427.58 cm , which correspond to the
symmetric and anti-symmetric stretching mode of carboxylate group [29, 30]. The peak around
-
1
-
1
1
027.55 cm is attributed to C–O bond [31]. As seen in (Figure 4), the bands correspond to
o
O–H group, NO
3
, and carboxylate ligand disappears as the gel which was calcinated at 700 C.
This indicates the possibility of metal carboxylate dissociation and conversion to metal oxides
-
1
during the calcination process. Also, the observed peak at about 607.20 cm is due to the
stretching internal vibrations of octahedral oxygen in nickel ferrite oxide structure.
In the FT-IR spectrum Schiff base nickel ferrite nanoparticles deposited on the surface,
-
1
Figure 4 (c), the broad peak in 1200-1000 cm belongs to Si-O-Si stretching vibration. In
-
1
addition, a peak at 1652 cm observed is attributed to the stretching vibration of C=N bond.
Bull. Chem. Soc. Ethiop. 2018, 32(1)

82
Narjes Babadi et al.
o
Figure 4. FT-IR spectra of NiFe
2 4
O nanopowders (a) and the calcinated powders at 700 C (b),
and spectra of NiFe O @SalenSi nano adsorbents (c).
2
4
Vibrating sample magnetometer (VSM) analyses
Ferromagnetism properties of the NiFe O at room temperature are shown in Figure 5 (a, b). (a)
2
4
s s
The saturation magnetization (M ) is 9.87 emu/g. The high M and low remnant magnetization
(
M = 43.616 emu/g) means that NiFe O can be separated easily from solution under an external
r
2
4
magnetic field and distribute well in reused cycles, which is favorable for reusing of the
adsorbent. (b) Ferromagnetism properties of the NiFe @SalenSi also include the saturation
magnetization (Ms) of 10.42 emu/g. The high M and low remnant magnetization (M = 54.125
2
O
4
s
r
emu/g).
Figure 5. VSM
spectra
of
NiFe
2
O
4
nanopowders
(a)
and VSM
spectra
of
NiFe O @SalenSinanoadsorbents (b).
2 4
Adsorption study
Effect of pH
The solution pH is an important parameter that affects the adsorption of Ni(II). The effect of the
initial solution pH on the metals removal efficiency of Ni(II) by NiFe O @SalenSi nanoparticles
2
4
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Synthesis and characterization of nanocomposite NiFe
2
O
4
@SalenSi
83
was evaluated at different pH values, ranging from 2 to 11, with a stirring time of 45 min. The
initial concentrations of Ni(II) and adsorbent dosage were set at 10 mg/L and 15.0 mg/L,
respectively. As shown in Figure 6, pH 9 seems to lead to the best result; so this pH was
selected to run further experiments.
1
00
90
80
70
60
50
40
30
20
10
0
0
5
10
15
pH
Figure 6. Effect of pH on Ni(II) adsorption onto NiFe O @SalenSi nanoadsorbents. (Initial
2
4
Ni(II) concentration 10 mg/L, adsorbent dose 15.0 mg/L, shaking rate: 200 rpm,
contact time: 45 min).
Effect of contact time and adsorbent dosage
To further assessing of Ni(II) removal, the effects of contact time and adsorbent concentration
on the removal of Ni(II) by NiFe O @SalenSi nanoparticles were examined. Ni(II)
2 4
concentrations and pH of the solutions were fixed at 10 mg/L and 9 respectively for all batch
experiments. Results are shown in. Figure7. As indicated, increasing of contact time in different
dosages of adsorbent led to decrease the concentration of Ni(II). This behavior was also
observed when the adsorbent dosage increased from 10.0 and 15.0 to 20.0 mg/L. This
decreasing in the concentration is due to the adsorption of Ni(II) on NiFe
nanoparticles and the greater number of adsorption sites for Ni(II) made available at greater
NiFe @SalenSi dosages. The removal efficiency of Ni(II) at the initial dosage of 15.0 mg/L,
and 45 min by keeping constant stirring was attained about 94.6%.
2 4
O @SalenSi
2
O
4
1
00
90
80
70
0
.02
.03
0
0.04
2
0
70
120
Time(min)
Figure 7. Effect of contact time on the removal of Ni(II) at different initial. (Initial Ni(II)
concentrations: 10 mg/L, shaking rate: 200 rpm, initial pH: 9).
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84
Narjes Babadi et al.
96
94
92
90
88
86
0
10
20
30
40
50
60
Ni+2 Concentration
Figure 8. Effect of initial metal ion concentration on removal of Ni(II). (Initial pH: 9, adsorbent
dose 15.0 mg/L, shaking rate: 200 rpm, contact time: 45 min).
Effect of Ni(II) concentration
The Ni(II) concentration is another important parameter that can affect the adsorption process.
The effect of initial Ni(II) concentration on metal removal efficiency by NiFe O @SalenSi
2 4
particles was studied by varying the initial Ni(II) concentration from 10 to 50 mg/L at pH 9, a
nanoadsorbent dosage of 15.0 mg/L and contact time of 45 min, as shown in Figure 8. Results
verify that metal removal of Ni(II) decreases with increasing the initial concentration.
Obviously, the percentage removal of Ni(II)was around 94.6% at a concentration of 10 mg/L .
2 4
Reusability of nano adsorbent NiFe O @SalenSi
Figure 9 shows the removal efficiency, R (%), of Ni(II), during five cycles of adsorption–
desorption–regeneration, from a 20 mL solution of initial Ni(II) concentration 10 mg/Lat pH 9.
As can be seen, no significant decrease in the adsorption capacity of NiFe
nanoadsorbent during the five cycles was observed. The results demonstrated that
NiFe @SalenSi nanoadsorbent can be used for the removal and recovery of metal ions from
2 4
O @SalenSi
2
O
4
wastewater over a number of cycles, indicating its suitability for the design of a continuous
process. It is noteworthy that commercially available adsorbents such as activated carbon are
costly, time-consuming and their regeneration is essential. Actually, the regeneration and
recovery of spent activated carbons is the most expensive part of the adsorption technology and
it accounts for about 75% of the total operating and maintenance costs [32]. However, it seems
that this is not the case for the regeneration of spent NiFe
Therefore, NiFe @SalenSi nanoadsorbent is a cost-effective alternative with fast adsorption
rate and its regeneration is simple and may be not necessary, especially for in situ applications
33].
2 4
O @SalenSi nanoadsorbents.
2
O
4
[
Adsorption kinetic studies
The kinetic studies describe that the solute uptake rate for choosing optimum operating
conditions for designing purposes. In order to investigate the mechanism of adsorption and
potential rate controlling steps such as chemical reaction, diffusion control and mass transport
process, kinetic models have been used to test experimental data from the adsorption of Ni(II).
These kinetic models were analyzed using pseudo-first-order and pseudo-second-order which
were respectively presented as follows in Eqs.
ꢄ
ꢅ
log(ꢀ − ꢀ ) = log ꢀ − ꢃ
ꢉ ꢊ
(3)
(4)
ꢁ
ꢂ
ꢁ
ꢆ/ꢇꢈꢇ
ꢂ
ꢍ
ꢍ
=
+ ꢋꢏ t
ꢋꢌ
ꢎꢆꢋ
ꢏ
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Synthesis and
c
haracterization of nanocomposite NiFe
2
4
O @SalenSi
85
where t is the contact time of adsorption experiment (min); q
e
(mg/g) and q
t
(mg/ gg ) are
respectively the adsorption capacity at equilibrium and at any time t. The values of t hh e rate
−
1
−1
constant, k
1 2
and k are -0.053 aa nd 0.161 (M min ), respectively.
The adsorption process of Ni(II) can be well fitted by using the pseudo-second ord
e
e
r rate.
stant.
an the R value (0.907) for first-order kinetics. This indicat ee s that
tic model provided good correlation for the adsorption of Ni(II)
2
The linear regression coeffic
Kinetics was closer to unity t
the pseudo-second-order kine
ions onto NiFe @SalenSi.
ii ent value R (0.999) obtained for pseudo-second-order co nn
2
h
h
t
2
O
4
100
9
4.49
94.6
9
2.47
89. 77 4
80
8
3.89
60
40
20
0
5
4
3
Cycel namber
2
1
22 4
Figure 9. Reusability of NiFe O @SalenSi nanoadsorbents for adsorption/desorption of Ni(II)
concentration 10 mg/L, adsorbent dose 15.0 mg/L, shaking rate: 200 rpm, cc ontact
time: 45 min, initial pp H: 9).
Adsorption isotherm studies
Adsorption isotherm studies a
n
n
alysis of the equilibrium data is important to develop an equation
e results which could be used for designing purposes. The esults
II) ions were analyzed by the use of well-known models given by
metal
whereas solution pH and amount of adsorbent were held con ss tant.
which accurately represents t
hh
rr
obtained for adsorption of Ni
((
the Langmuir, Freundlich and Temkin isotherm models. For the sorption isotherms, initia
ll
ion concentration was varied
w
Ce
1
Ce
(5)
6)
(7)
ration in the solution (mg/L), q is the Ni(II) concentration in the


qe
klqmax qmax
1
(
log q  log K

F
log Ce
e
n
qe  A  Bln Ce
where C is the Ni(II) concen
tt
e
e
solid adsorbent (mg/g), q
the energy of adsorption (L/g
m
is t
h
e maximum adsorption capacity (mg/g), K
l
is a constant related to
nstant
rption
)
, K and n are constants of the Freundlich equation. The coo
F
K
F
represents the capacity of the adsorbent for the adsorbate and n is related to the adsoo
1
-1/n
1/n
distribution (mg
L /g), A (L/g) is Temkin constant representing adsorbent–adsorbate
-
1
2
interactions and B (mg .L ) i
ss
another constant related with adsorption heat. The R val uu es for
Bull. Chem. Soc. Ethiop. 2018, 32(1)

86
Narjes Babadi et al.
2
the Freundlich model (R = 0.999) are closer to unity than those for the other isotherm models
2
2
(
Langmuir: R = 0.958 and Temkin: R = 0.955) for adsorption process onto NiFe O @SalenSi.
2 4
2 4
This indicates that the adsorption of Ni(II) on NiFe O @SalenSi particles is better described by
the Freundlich model than the Langmuir and Temkin models and generally it has been found
better suited for characterizing monolayer adsorption process onto the homogenous adsorbent
surface (Figure 10 (a, b, c)) [34].
2 4
Figure 10. Isotherm plots of Ni(II) adsorption onto NiFe O @SalenSi nanoadsorbents. (Initial
Ni(II) concentration 10 mg/L, adsorbent dose 15.0 mg/L, shaking rate: 200 rpm,
contact time: 45min, initial pH: 9). a: Langmuir isotherm, b: Freundlich isotherm and
c: Temkin isotherm.
CONCLUSION
This study showed that NiFe
conventional adsorbents for the removal of metal ions from wastewater in a very short time with
high removal efficiency, whereas, single NiFe was not be able to removal of metal ions. The
removal of Ni(II), as a typical metal ion commonly present in wastewater, by adsorption onto
NiFe @SalenSi nanoadsorbents was successfully accomplished. Adsorption was very rapid
2 4
O @SalenSi nanoadsorbent could be used as an alternate to
2
O
4
2
O
4
and equilibrium was achieved in less than 45 min. Also the adsorption was highly dependent on
the initial concentration of Ni(II) and pH. Maximum removal was observed at pH 9. Adsorption
increased as the initial concentration of Ni(II). The adsorption isotherms were also determined
and were appropriately described by both Langmuir and Freundlich models, with a better fitting
to the Freundlich model than the Langmuir model. Therefore, NiFe O @SalenSi nanoadsorbents
2 4
are recommended as fast, effective and inexpensive adsorbents for rapid removal and recovery
Bull. Chem. Soc. Ethiop. 2018, 32(1)

Synthesis and characterization of nanocomposite NiFe
2
O
4
@SalenSi
87
of metal ions from wastewater effluents. The pseudo-second-order kinetic model provided good
correlation for the adsorption of Ni(II) ions onto NiFe @SalenSi. The desorption and
regeneration studies indicated that nanoadsorbents can be used repeatedly, without impacting
the adsorption capacity. Therefore, NiFe @SalenSi nanoadsorbents are recommended as fast,
2
O
4
2
O
4
effective and inexpensive adsorbents for rapid removal and recovery of metal ions from
wastewater effluents.
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Gómez-Álvarez, A.; Valenzuela-García, J.L.; Meza-Figueroa, D.; De, M.; O-Villanueva,
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