Fabrication and covalent modification of highly chelated hybrid material based on silica-bipyridine framework for efficient adsorption of heavy metals: Isotherms, kinetics and thermodynamics studies

Article abstract of DOI:10.1039/c6ra14349k

Adsorbent materials are essential in clean-up processes. Research of efficient materials is a well-established technology. In this work, a novel and excellent host for heavy metals was synthesized by covalent immobilization of bipyridine tripodal receptor onto silica particles. The new engineered surface was well analyzed and evaluated by BET, BJH, EA, FT-IR, SEM, TGA and solid-state ¹³C NMR. The adsorption properties were investigated using Pb(ii), Cd(ii), Zn(ii) and Cu(ii) metals by varying all relevant parameters such as pH, contact time, concentration, thermodynamic parameters, kinetics, Langmuir and Freundlich isotherms, etc. The hybrid material has been found to exhibit high distribution coefficients for heavy metals. Adsorption kinetics follows a pseudo-second-order model, as a rapid process as evidenced by equilibrium achieved within 20 min. The resulting adsorption isotherms of the material were better represented by the Langmuir model than the Freundlich model. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) revealed that the adsorption was endothermic and spontaneous. In addition, the proposed material demonstrates a high degree of reusability over a number of cycles, thus enhancing its potential for application in heavy metals recycling. All metal ions were determined by atomic absorption measurements.

Full text of DOI:10.1039/c6ra14349k

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ARTICLE
Fabrication and Covalent Modification of Highly Chelate Hybrid
Material Based on Silica-Bipyridine Framework for Efficient
Adsorption of Heavy Metals: Isotherms, Kinetics and
Thermodynamics Studies
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
*
a,b
a
c
c
c
Smaail Radi, Said Tighadouini, Maryse Bacquet, Stéphanie Degoutin, Ludovic JANUS, and
www.rsc.org/
d
Yahia N. Mabkhot
Adsorbent materials are essential in the cleanup process. Research of efficient materials is a well
established technology. In this work, a novel and excellent host for heavy metals was synthesized by
covalent immobilization of bipyridine tripodal receptor onto silica particles. The new engineered
1
3
surface was well analyzed and evaluated by BET, BJH, EA, FT-IR, SEM, TGA and solid state C NMR.
The adsorption properties were investigated using Pb(II), Cd(II), Zn(II) and Cu(II) metals by varying all
relevant parameters such as pH, contact time, concentration, thermodynamic parameters, kinetics,
Langmuir and Freundlich isotherms, etc… The hybrid material has been found to exhibit higher
distribution coefficients for heavy metals. Adsorption kinetics follows a pseudo-second-order model,
with rapid process as evidenced by equilibrium achieved within 20 min. The resulting adsorption
isotherms of the material were better represented by the Langmuir model than the Freundlich
model. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) revealed that the adsorption was
endothermic and spontaneous. In addition, the proposed material demonstrates a high degree of
reusability over a number of cycles, thus enhancing its potential for application in heavy metals
recycling. All metal ions were determined by atomic absorption measurements.
1
3
from aqueous solution, such as activated carbon , clays
14
18
,
.
1
chelating resin , cellulose , zeolites , and silica gel
5
16
17
Introduction
Nevertheless, it is of importance to further develop cheaper
and available adsorbent with good performance.
Water pollution caused by heavy metal ions has become a
major issue globally due to their persistence and harmful
To this end, silica-based organic-inorganic hybrids have rapidly
emerged as a versatile and attractive class of adsorbents with
advanced properties that are often difficult to achieve either
from totally inorganic or from totally organic materials. These
hybrids are robust solids displaying both: (i) high specific
surface area, (ii) three dimensional structure giving rise to
highly and regularly porous framework, (iii) good mechanical
and hydrothermal stabilities, (iv) exceptionally good
accessibility to active centers, (v) fast mass transport rates
1
,2
3-5
effects upon aquatic life, human health and environment
It has been reported that metals such as lead (Pb), cadmium
Cd), Zinc (Zn) and Copper (Cu) are among the most hazardous
and are included on the US Environmental Protection Agency’s
EPA) list of priority pollutants. Therefore, their removal of
.
(
(
from natural and waste water has been drawing more and
more attention.
Several techniques have been developed for the removal of
these toxic metals from aqueous solution such as ion exchange
inside the porous structure, and (vi) can be manufactured
6
7
reverse osmosis , adsorption
8,9
10
precipitation , and
,
19-22
quite easily under mild conditions
these organic-inorganic hybrids have become powerful
. Indeed, in recent years,
1
1
filtration . Compared with other techniques, adsorption is
considered to be one of the most promising and widely
23,24
adsorbent materials for removal of organic
and inorganic
contaminants from waters and wastewaters. Furthermore,
the silica network exhibits good mechanical properties and
stability in a wide range of pH. Also, it can be easily derivatized
to a variety of organic functionalities by chemical and covalent
applied methods owing to its low cost, high efficiency, simple 25-29
feature to operate, and reversibility . Many kinds of
adsorbents have been used for the removal of heavy metals
1
2
30-36
a.
coupling
corresponding sepharoses
, and it is much less expensive than the
.
Laboratoire de Chimie Appliquée et Environnement (LCAE), Faculté des Sciences,
3
7
Université Mohamed I, 60 000 Oujda, Morocco. E-mail : radi_smaail@yahoo.fr;
Tel: +212536500601; Fax: +212536500603
Centre de l’Oriental des Sciences et Technologies de l’Eau (COSTE), Université Med
Some Organic-inorganic hybrid materials containing pyridine
derivatives were already reported, showing high bond stability
b.
I, 60 000 Oujda, Morocco.
Université Lille 1, Unité Matériaux et Transformations (UMET) UMR CNRS 8207,
3
8-40
c.
for transition metal
. In this context, the ability of pyridine
5
9655 Villeneuve d’Asc Cedex, France.
d.
Department of Chemistry, Faculty of Science, King Saud University, P.O. Box 2455,
Riyadh 11451, Saudi Arabia.
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and its derivatives to act as ligands with sp2 hybrid nitrogen surface were then reacted with the ligand (L ) under gentle
2
donors have been the research subjects of many conditions to form the new chelating adsorbent SiNPr
2
(Schema 1).
preconcentration and coordination chemists. This is evident Surface of adsorbent was determined on the basis of the
corresponding analytical and spectroscopic data.
4
1-43
from the large number of articles on this topic
.
We therefore propose the use of a new designed pyridine ligand
with the aim of developing a selective recovery system for heavy Characterization of the materials
metals. Indeed, we successfully fabricate new highly chelated
Elemental analysis: The surface immobilization of silica particles
was confirmed by the presence of carbon and nitrogen in the
modified materials, which were primarily absent in native silica. The
hybrid material based on silica-supporting N,N-bipyridine
tripodal ligand. The active donor atoms (of grafted ligand) are
so oriented to act as a convergent chelating bidentate donor elemental analysis in each synthetic step is shown in Table 1; the C
due to the possible coordination to the same metal center, and N content appeared in SiNH indicated the successful
forming thus a more stable five-membered ring . The aminopropylation reaction. In the final step, the increase of C and N
2
3
8
content in SiNPr
attached to SiNH2.
2 2
indicated that the ligand (L ) was perfectly
synthesized adsorbent showed high affinity, high adsorption
capacity and less equilibrium time for efficient removal of
heavy metals. Parameters that can affect the sorption
efficiency of the metal ions: Pb(II), Cd(II), Zn(II) and Cu(II) were
studied in aqueous solutions using atomic absorption.
Table1. Elemental analysis
Sample
SiNH
SiNPr
%C
%N
2
4.46 ± 0.06
6.21 ± 0.04
1.66 ± 0.02
1.82 ± 0.05
2
Results and discussion
Linker synthesis
FT-IR characterization: The modified silica was also confirmed by
FT-IR analysis, as shown in Fig.1. A characteristic feature of the 3-
The synthetic procedure for the new organic-inorganic hybrid
material can be summarized in Scheme 1. The first stage of the
amonopropylsilica (SiNH
2
) (b) when compared with the native silica
-1
(
a) was the appearance of a ν(NH ) around 1560 cm and a ν(C-H)
2
preparation was the synthesis of ligand (L
carried out from ethyl picolinate which was converted in the
presence of lithium aluminum hydride to the hydroxyl product (L ).
The last product was then chlorinated using thionyl chloride to give
the desired product (L ). The structure of compounds was
2
). The reaction was
-1
weak bands at 2941 cm corresponding to the carbon chain of the
pendant group attached to the inorganic silica matrix. The spectrum
1
of the final material (SiNPr ) (c) reveals the disappearance of the
2
-1
absorption band at 1560 cm due to the reaction of the primary
2
2
amine (-NH ) and the appearance of new characteristic bonds
determined on the basis of the corresponding analytical and
spectroscopic data.
The second stage involves reacting the activated silica with 3-
aminopropyltrimethoxysilane in toluene to form the amino groups
-1
-1
around 1552 cm and 1451 cm resulted from C=N and C=C
vibration respectively. These results showed that the
methylpyridine units had been grafted onto the surface of silica gel
after modification.
2
attached to the silica surface. These NH -groups onto the silica
8
7
7
6
6
5
5
4
4
3
3
2
2
1
1
0
5
0
5
0
5
0
5
0
5
0
5
0
5
0
5
0
5
(SiNP2)
1459.15
(SiG)
1531.77
1600
970
(SiNH2)
3446
1582.35
1100
2932.66
-
4
500
4000
3500
3000
2500
2000
1500
1000
500
-
1
cm
Scheme 1. Synthesis route of modified chelating material.
2 2
Fig. 1. FT-IR spectra of native silica (SiG), SiNH and SiNPr
Scanning electron micrographs (SEM): Micrographs were obtained
on the native silica and chemically modified materials (SiNH
2
and
SiNPr ) in order to detect differences in their surfaces (Fig.2). The
2
surface of the native silica is composed of a macro particle
structure. After the modification, the surface was changed. It was
evident that the loaded functional groups were distributed on the
whole surface that made the surface of the product SiNPr
rough.
2
become
2 2
Fig. 2. SEM images of native silica (A), SiNH (B) and SiNPr (C).
2
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Thermogravimetric analysis (TGA): The TGA curve reflect the Surface properties: The surface areas for the materials were
thermal stability and the degradation process of the materials. determined through the BET method and gave the results as SBET of
Curves of the native silica, SiNH and SiNPr have been established native silica > SiNH > SiNPr . The decrease in surface area (Fig.5)
2
2
◦
2
2
◦
at the temperature range of 25 C to 800 C, and the results are after incorporation of organic groups can be easily interpreted by
shown in Fig.3. The profile confirms the high thermal stability for the presence of pendant organic groups which partially block the
the prepared material. Indeed, the native silica presents a first mass adsorption of nitrogen molecules on surface and consequently
◦
loss stage of 3.15% in the interval of 25 C to 110°C assigned to cause a decrease in the surface area. This hindrance is more
◦
physically adsorbed water, and a second loss of 5.85% from 110 C to pronounced for the largest organic moiety, originating from the
8
00°C assigned to condensation of the free silanol groups which bipyridine tripodal units. Moreover, the isotherm curves are of type
4
4-45
causes siloxane bond formation (Si-O-Si)
. Again two distinct IV according to the classification of IUPAC and show for partial
mass loss steps were detected for the SiNH sample. The first one pressures P/P0 > 0.4 a pronounced hysteresis. In addition, the
2
was a small mass loss of 1.56% in the room temperature to 100 °C hysteresis loops are of type H2 which indicates that there is a
range attributed to the remaining silanol hydration water. The uniform pore diameter distribution.
second mass loss increase of 9.77% was observed between 208 and Table 2, summarized the physical parameters for the native silica,
8
00°C, which correspond to the organic matter immobilized on the SiNH and SiNPr that were calculated from nitrogen adsorption-
2 2
2
surface. The final SiNPr material presented two distinct mass loss desorption isotherms. It was observed that the surface area and
stages. Following the preceding interpretation, the first mass loss of total pore volume decrease in sequence, respectively. The results
.01% in the 25-109°C range is assigned to adsorbed water, and can be attributed to the introduction of organic functional groups
other mass loss of 10.6% between 242 and 800°C is attributed to into the mesoporous channels which may reduce the pore size and
2
46-48
the decomposition of the pyridine fraction immobilized on the increase the density of material
surface of silica, together with the condensation of the remaining
silanol groups. The pronounced increase in mass loss reflects the
higher amount of the anchored organic groups.
.
Fig. 5. Nitrogen adsorption-desorption isotherm plots of SiNH
Table 2. Physical properties of silica derivatives
2 2
and SiNPr
2 2
Fig. 3. Thermogravimetric profiles of native silica (a), SiNH (b) and SiNPr (c).
1
3
C-NMR characterization: Important features related to
immobilization of pendant group on the inorganic structure of the
1
3
hybrid formed can be obtained through C NMR spectra in solid
state (Fig. 4). Indeed, spectrum of SiNH
Specific surface
Pore volume
(cm g )
Silica derivatives
Native silica
45
2
−1
3
−1
2
presented three well-
S
BET (m g )
formed peaks, at 9.02, 24.79 and 42.62 ppm attributed to the
propyl carbon. The signal at 50.62 ppm was assigned to the carbon
of unreacted methoxy. Spectrum of SiNPr material showed peaks
2
in the range of 122–156 ppm referred to carbon atoms of
dimethylpyridine units.
305.21
283.08
272.09
±
±
±
0.79
0.77
0.99
0.770
±
±
±
0.002
SiNH
SiNPr2
2
0.690
0.680
0.002
0.011
Chemical stability: Chemical stability of the newly synthesized
material SiNPr was examined in various acidic and buffer solutions
pH 1-7). No destruction in the material structure was noticed even
2
(
after 24h of contact justified by elemental analysis. The high
stability exhibited by the attached organofunctional group is
presumably due to the pendant group. It has been shown that
when the length of the hydrocarbon bridge was more than two
methylene groups, the rupture of Si–C bond did not occur in a
mineral acid medium, due to the length of the chain; longer chains
can no longer have a functional handle that can undergo beta-
4
9-50
elimination of the Si cation
.
1
3
2 2
Fig. 4. C NMR spectra of SiNH and SiNPr
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Heavy metal adsorption
Effect of pH: pH is one of the main variables affecting the sorption
process, the speciation of the metal ions, the surface charge of the
sorbent and the degree of ionization of the adsorbate during the
5
1
reaction . Indeed, the effect of solution pH on the removal of
Pb(II), Zn(II), Cu(II) and Cd(II) by SiNPr was determined within the
2
pH range of 1-7 and the results are given in Fig.6. The removal of
metals increased with the increase in solution pH. The maximum
removal of Pb(II), Zn(II), Cu(II) was observed at pH 6-7 while for
Cd(II), it was in the range 5-7.
At lower pH values, the retention of metal ions by the
2
functionalized silica SiNPr is not significant since the donor atoms
of the ligand must be almost entirely in its protonated form and a
low interaction or a strong electrical repulsion forces occurred
between the donor atoms and the metal ions. With increasing pH,
the protonation becomes weak, and the interactions donor atoms
with metal ions become stronger, which enhances the chelation
and adsorption of metal ions. Over pH 7, the variation of metal
species in solutions occurred because of the hydrolysis of metal
Fig.6. Effect of pH on the adsorption of metal ions on SiNPr2, at
optimum concentration, t = 60 min and Temp: 25°C. The coefficients of
variation were lower than 5 % for the data presented.
2
ions; leading to the precipitation of metal hydroxide M(OH) , this
makes it difficult to distinguish between the M(II) hydrolyzed or
adsorbed.
This is consistent with the point of zero charge (PZC)
corresponding to the pH of the medium at which the material
surface charge is zero. Indeed, the pHPZC value of native silica
52
.
was 2.3, determined by using a simple described method
Surface coverage of SiNPr leads to an increase of the PZC to
2
give pHPZC 6.3 due to the basicity of the ligand used. This pHPZC
corresponds to the total deprotonation of the ligand, and
therefore to a maximum sorption of metal ions.
Effect of Adsorption kinetics: The kinetics of the adsorption
process was investigated to study the effect of the initial concentration
of metal ions on the qe with respect to time, and the time required to
53
achieve equilibrium between aqueous and solid phase . The kinetics
study was carried out using optimum pH, optimum concentration and
temperature at 25°C. Two simple kinetic models, namely the pseudo-
54
first-order (equation 1) and the pseudo-second-order (equation 2)
are the most often used to analyze the rate of sorption:
Fig.7. Effect of shaking time on the adsorption capacity of Pb(II),
Zn(II), Cu(II) and Cd(II) at optimum pH, optimum concentration and
Temp: 25°C. The coefficients of variation were lower than 5 % for the
data presented.
ln(q
e
– q
t
) = ln q
e
– k
1
t
(1)
t
1
1
(2)
=
+
t
2
qt k2 qe
qe
On the other hand, the rate of metal ions adsorption is one of the
important characteristics that define the efficiency of sorption. It
was evaluated by fitting the experimental data to the linear form of
pseudo-first-order and pseudo-second-order kinetics using
equations (1) and (2) respectively. The fitted kinetic parameters are
summarized in Table 3. The results show that the pseudo-second-
where q
e t
and q are the amounts of metal ions adsorbed on the
-
1
adsorbent (mg.g ) at equilibrium and at time t, respectively. k
1
and
2
(min ) are the rate constant of the pseudo-first-order and the
-1
k
pseudo-second-order adsorption respectively.
The effect of contact time on the adsorption of metals by SiNPr
2
material is shown in Fig.7. Indeed, the kinetic curve showed that the
adsorption was rapid and the plateau was reached after about 20
min of contact. The rapid adsorption can be explained by the
availability and the orientation of the three nitrogens (active
donor atoms), as convergent chelating sites, in the
coordination of metal ions forming thus a more stable five-
2
order model has a better correlation coefficient R . Moreover, the
calculated values of qe by this model are also much closer to the
experimental data than those of the pseudo-first-order kinetic
model. These results suggested that the chemical process was likely
55
to be the rate-limiting step of the adsorption mechanism
. Indeed,
3
8
it is well known that the pseudo-second order equation may
be applied for chemisorptions processes with a high degree of
correlation in several literature cases where a pseudo-first
order rate mechanism has been arbitrarily assumed.
membered ring
.
We also note that the adsorption affinity depends on several
factors such as the nature, charge and size of metal ions, and
the affinity of donor atoms towards each metal. It is therefore
not surprising to have different affinities and adsorption of the
same adsorbent with respect to different metals.
4
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Table 3. Kinetics of heavy metals removal onto SiNPr
2
Parameters
Metal
Pb(II)
99.68
Zn(II)
82.68
Cu(II)
64.84
Cd(II)
42.18
q
e(exp) (mg/g)
Pseudo-first-
order
q
k
e
(mg/g)
30.63
0.118
0.991
15.95
0.108
0.923
09.55
0.108
0.978
30.16
0.251
0.921
-1
1
(min )
2
R
Pseudo-second-
order
q
e
(mg/g)
100.00
15.87.10
0.995
83.33
28.80.10
0.997
64.93
51.56.10
0.998
42.91
38.24.10
0.995
-3
-3
-3
-3
k
2
(g/mg min)
2
R
Fig.8. Effect of concentration on metal ion adsorption onto SiNPr
2
adsorption dose: 10mg, V=10ml, Temp: 25°C and pH=6 for Pb(II),
Zn(II), Cu(II) and Cd(II). The coefficients of variation were lower than 5
Adsorption isotherms: In order to determine the relationship
between the amount of metal ions adsorbed and the concentration
of remaining metal ions in the aqueous phase, the adsorption
isotherm studies were performed at equilibrium conditions. These
adsorption data for each metal ions were fitted into both the
Langmuir and Freundlich isotherm equations. The Langmuir
isotherm described the monolayer sorption of metal ions on the
surface of the sorbent, while The Freundlich isotherm model
described both multilayer sorption and sorption on heterogeneous
surfaces. The linearized from of the Langmuir isotherm (equation 3)
%
for the data presented.
Thermodynamic studies : In order to evaluate the temperature
effect on the sorption, the experimental values were fitted to the
plots of the distribution coefficient value K
temperature. The thermodynamic of metal ions sorption onto
SiNPr from aqueous solution were studied between 25-45°C. The
thermodynamic parameters such as change in Gibbs free energy
d
as a function of
2
5
6-57
58
and the Freundlich isotherm (equation 4) are expressed as
follows:
(
ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were determined using the
5
9
following equations
:
C − Ce
Ce
V
0
Ce Ce
1
Kd =
(5)
(
3)
=
+
m
qe
q
qKL
0
0
lnCe
ꢀS
R
ꢀH
RT
ln Kd =
−
(6)
ln q = ln K +
(4)
e
F
n
0
0
0
ꢀ
G = ꢀH − TꢀS
(7)
e
where q is the amount of solute sorbed on the surface of the
-1
sorbent (mg.g ), C is the equilibrium ion concentration in the where C (mg/L) is the initial concentration of metal solution, Ce
e
0
-1
-1
solution (mg.L ), q is the saturated adsorption capacity (mg.g ) and (mg/L) is the equilibrium concentration, V(mL) is the volume of
n is the Freundlich constant. KL (L.g ) and K (mg.g ) are the solution, m (g) is the dosage of sorbents, R is the universal gas
-1
-1
F
Langmuir and the Freundlich adsorption constants respectively.
constant (8.314 J/mol.K) and T(K) is the absolute temperature.
The adsorption behavior of heavy metal ions onto the adsorbent
SiNPr at different initial heavy metal ions concentration was
2
Table 4. Adsorption isotherm parameters for the removal of heavy metals
onto SiNPr
2
investigated in Fig.8. The isotherms showed a sharp initial slope
indicating that the material acts as a high efficiency adsorbent at
low metal concentration. In addition, when aqueous Pb(II), Zn(II),
Cu(II) and Cd(II) concentration increased, the saturation constant
value were reached.
Metal
Langmuir isotherm model
Freundlich isotherm model
2
R
2
R
q
K
L
K
F
n
(mg/g)
111.11
91.743
68.027
45.045
(L/mg)
0.061
0.072
0.221
0.139
(mg/g)
8.490
7.42
Parameters of the Langmuir and Freundlich models were calculated
by plotting the Ce/qe versus Ce and lnqe versus lnCe plots,
respectively. The fitted curve of linear Langmuir model is given in
Fig.10. The Langmuir and Freundlich isotherm parameters for
adsorption of Pb(II), Zn(II), Cu(II) and Cd(II) are given in Table 4.
Pb(II)
Zn(II)
Cu(II)
Cd(II)
0.991
0.991
0.997
0.994
1.88
1.808
2.529
2.794
0.942
0.939
0.823
0.824
12.54
8.985
2
Comparison of the R values shows that the Langmuir isotherm
The thermodynamics of Pb(II), Zn(II), Cu(II) and Cd(II) sorption onto
SiNPr from aqueous solution was studied between 25-45°C using
2
fitted quite well with the experimental data (R > 0.99), indicating a
2
uniform solid surface on the sorbent, and a regular monolayer
sorption.
optimum concentration of all metal ions (Fig.9). The ΔH°, ΔS° and
ΔG° values were obtained from the slop and intercept of lnkd verses
1
/T using the equations (5), (6) and (7) respectively.
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Fig.10. Effect of foreign metal ions
Fig.9. Effect of temperature for the sorption of metal ions onto
SiNPr (shaking time 60 min, pH = 6, V =10 mL, m =10mg of SiNPr
at optimum concentration)
2
2
2
Applicability of SiNPr for extraction of heavy metals from real
samples: The applicability of the studied adsorbent was tested
by its application for removal of Pb(II) and Zn(II) from water
samples. To this end, two water samples were collected, (i)
Ghiss River (Al Hociema) and (ii) Touissit-boubekker River
Table 5 results showed that the values of ΔG° are negative at all
studied temperature, indicating the spontaneous nature of the
adsorption process. The positive values of enthalpy ΔH° showed
that the adsorption is endothermic. The positive value of ΔS°
reveals the increase in randomness at solid solution interface
(Jerada-Oujda), using polyethylene bottle and filtered through
a nylon 0.45μm. As the selected samples do not contain lead,
we proceeded by adding an optimal concentration of standard
Pb(II) (150 mg/g) to solutions. This investigation revealed
2
during the adsorption of all four ions onto SiNPr .
(
Table 6) that significant elimination of existing metals can be
Selectivity of SiNPr2 : The competitive adsorption experiments of
Pb(II) by the SiNPr were carried out from the mixed Pb(II)-Zn(II)-
Cu(II)-Cd(II) quaternary system using the aqueous solution
containing optimum concentration of each metal ions, through
batch method. Fig.10 shows the adsorption capacity of metal ions in
achieved in less than one hour of contact. However, the
extraction seems to decrease compared to the value obtained
in aqueous solutions because of possible interference with the
organic matter and alkali metals naturally existing in the real
water.
2
2
the quaternary system. It can be seen that the SiNPr has excellent
adsorption and high affinity especially for Pb(II). However, the
extraction seems to decrease compared to the value obtained in
the absence of foreign metal ions. Yet, the remarkable selectivity
toward Pb(II) favorites the material to be used as a good promising
potential adsorbent, for the removal of Pb(II) from aqueous
solutions containing competing ions.
Table 6. Results of the application of SiNPr
2
for extraction of
heavy metals from water samples (with and without adding
1
2
50 mg/L of Pb ).
+
water samples
Metal
ion
C
found ± 0.05
(mg/L)
Adsorption
capacity
Adsorption
capacity
b
c
(
mg/g)
(mg/g)
Table 5. Adsorption models used in this work and their parameters
Zn(II)
Cd(II)
Cu(II)
Pb(II)
Zn(II)
Cd(II)
Cu(II)
Pb(II)
1.15
1.45
nd
nd
12.05
2.25
nd
0.4
0.02
-
-
6.35
0.41
-
-
-
-
Ghiss river
(Al Hociema)
-
1
-1
-1
-1
a
Metal
ΔH°(kJ mol )
ΔS°(Jk mol )
T(°C) ±1°C
ΔG°(kJmol )
70.65
Pb(II)
4.33
14.77
25
-0.08
-0.22
-0.37
-0.08
-0.47
-0.85
-0.92
-1.53
-2.15
-0.40
-1.74
-0.78
-
-
-
3
4
5
5
Touissit river
(
Jerada)
Zn(II)
Cu(II)
Cd(II)
11.46
17.46
9.92
38.62
61.46
34.53
25
nd
-
72.39
3
4
5
5
a
b
c
nd: not detectable.
adsorption capacity without adding lead
adsorption capacity with adding 150 mg/L of lead
25
3
4
5
5
2
Regenerability of SiNPr : The sample was easily regenerated by
25
soaking the sample in 6N HCl for a few minutes (5-10 mL of 6N HCl
per g of support). This new solid extractor has a good stability and
can be reused many times without decreasing its extraction
percentage. Indeed, after five cycles of adsorbent regeneration
3
4
5
5
(
Table 7), no significant change in the percentages of adsorption
was observedة which is remarkable. The stability of the organic
groups onto the solid surface was also confirmed by TGA, with no
distinct changes in the sorbent material being observed after five
6
| J. Name., 2016, 00, 1-3
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cycles. This suggests that SiNPr2 has excellent chemical stability as a These results suggest that this newly material is potential for
highly efficient adsorbent for the recovery of heavy metals.
the removal of heavy metals form aqueous solution, thus
opening important perspectives.
Table 7. Adsorption / regeneration of hybrid material toward: Pb(II), Zn(II),
Cu(II) and Cd(II).
Experimental
Cycle number
Pb(II)
99.68
99.00
99.03
98.89
99.10
Zn(II)
82.68
82.12
82.08
81.87
81.80
Cu(II)
64.84
64.80
64.81
64.70
64.55
Cd(II)
42.18
42.01
42.03
42.06
42.01
1
2
3
4
5
Materials and methods
All solvents and other chemicals (Aldrich, purity > 99.5%) were of
analytical grade and used without further purification. Silica (E.
Merch) with particle size in the range of 70-230 mesh, median pore
diameter 60 Å, was activated before use by heating it at 160°C
during 24h. The silylating agent 3-aminopropyltrimethoxtsilane
Comparison with alternative sorbents: Table
8 shows the (Janssen Chimica) was used without purification. All metal ions
adsorption of Pb(II), by other sorbent reported in the literature. It is determined by atomic absorption measurements were performed
clear that the functionalized silica described in this work presents by Spectra Varian A.A. 400 spectrophotometer, equipped with air–
further improvement and shows better values and higher affinity acetylene flame. The wavelength used for monitoring Pb, Cd, Cu
for the effective adsorption for Pb(II).
and Zn is 283.3, 228.8, 324.8 and 213.9 nm, respectively. Metal ions
detection are in the range: 1-12 ppm, 0.1-0.6 ppm, 1-4 ppm and
0.1-0.6 ppm for Pb, Cd, Cu and Zn respectively. The calibration-
curve method was used to elucidate the results of measurements.
The pH value was controlled by a pH 2006, J. P. Selecta; s. a.
Elemental analyses were performed by Microanalysis Centre
Service (CNRS). FT-IR spectra were obtained with Perkin Elmer
System 2000. SEM image were obtained on an FEI-Quanta 200. The
mass loss determinations were performed in 90:10 oxygen/nitrogen
atmospheres on a Perkin Elmer Diamond TG/DTA, at a heating rate
of 10°C min . The C NMR spectrum of the solid state was
obtained with a CP MAX CXP 300MHz. A specific area of modified
silica was determined by using the BET equation. The nitrogen
adsorption-desorption was obtained by means of a Thermoquest
Sorpsomatic 1990 analyzer, after the material had been purged in a
stream of dry nitrogen.
Table 8. Comparison of the adsorption capacity (mg/g) of various sorbents
toward: Pb(II), Zn(II), Cu(II) and Cd(II) from the literatures.
Support : silica gel/ligand
This work
Pb(II) Zn(II) Cu(II) Cd(II)
Ref
99.68 82.68 64.84 42.18
-
TOES
75.60 71.50 54.70 65.80
52.41 35.72 61.52 38.45
[28]
[29b]
[29c]
[29e]
[60]
Nitrothiophene
C,N-Bipyrazole
Ketoenol Furane
Gallic acid
2.28
0.56
-
0
18.75 23.36 32.08 52.15
-1
13
12.63
64.61
23.70
-
-
-
15.38
-
6.09
Tris(2-aminoethyl) amine
36.42
[61]
3
-Aminopropyl
19.20 14.10
[62]
PMAEEDA
61.90 17.16 19.96 19.34
42.19 26.01 25.00 10.01
[63]
Dithiocarbamate
[64]
Conclusions
Syntheses
Synthesis of pyridine-2-ylmethanol: To a solution of LiAlH
0
3
after cooling water (5.66 mL), 15% aqueous sodium hydroxide (5.66
mL) and then water (17 mL) were added successively to the mixture
at 0°C. The solid material was filtered and the residue was washed
with hot THF. The filtrate and THF washing were concentrated
under reduced pressure. The residue was passed through a short
4
(5.66g;
.14 mol) in 90 mL of THF was slowly added ethyl picolinate (6g;
9.69 mmol) at 0°C. The mixture was stirred under reflux for 4h,
Based on the experimental results, the following conclusions
are made:
1
- Novel engineered material based on hybrid material
(SiNPr ) with highly chelate bipyridine receptor has been
successfully synthesized via
2
a simple heterogeneous
procedure and the surface was well characterized.
2- The adsorption depends on pH in the range from 1 to 7.
The maximum adsorption value of 99.68 mg/g, 82.68 mg/g,
silica column (CH
brown liquid; R = 50% (CH
ν(OH) = 3411; ν (C=N) = 1553; ν (C=C) = 1452; H NMR (DMSO-d6): δ
.53 (s, 2H, -CH ); 5.38 (s, 1H, OH); 7.21 (m, 1H, Py-H ); 7.44 (d, 1H,
Py-H ); 7.76 (t, 1H, Py-Hγ); 8.44 (d, 1H, Py-Hᾳ); C NMR (DMSO-d6):
δ 64.52 (1C, CH ); 120.60 (1C, Py-C ); 122.35 (1C, Py-C ); 137.02 (1C,
2
Cl
2
/MeOH, 9/1) to give a 86% yield of L
1
as a
6
4.84 mg/g and 42.18 mg/g for Pb(II), Zn(II), Cu(II) and Cd(II)
-1
f
2
Cl /MeOH, 9/1; silica); IR (KBr, cm ):
2
respectively, was obtained in the pH range 6-7, and can be
reached in only 20 min, suggesting rapid external diffusion
and surface adsorption.
1
4
2
β
13
δ
3
- The adsorption kinetics fit into the pseudo-second-order
model, and shows the homogeneous characteristics. The
comparison of different isotherm models indicated that the
Langmuir model gave the best fit to the experimental data.
2
β
δ
Py-C
δ
);+ 148.89 (1C, Py-Cᾳ); 162.31 (1C, Py-Cε); MS: m/z, 110.05
(
M+H) .
4-
The increase in adsorption capacity at increased Synthesis of 2-(chloromethyl)pyridine: A solution of 2.5 mL of
temperature indicates that the adsorption of heavy metals thionnyl chloride in 5 mL of methylene chloride was slowly added to
onto hybrid sorbent is endothermic in nature.
a compound L (1.5g; 13.74 mmol) in 30 mL of methylene chloride
1
5
- The functionalized material displayed an excellent at 0°C. This mixture was stirred for one night at room temperature.
adsorption capacity for Pb(II) in competitive mode and in The solvent was removed under reduced pressure and the residue
natural real water samples .
- The hybrid material (SiNPr
for heavy metal removal compared to literature reports.
was dissolved in 60 mL of ether. The mixture was then neutralized
) showed higher performance with about 10 mL of saturated sodium bicarbonate solution and the
6
7
2
ether solution was dried over anhydrous sodium sulfate. After
- The adsorbent can be regenerated several times without evaporating the mixture, the residue was filtered through a short
loss of its mining capacity.
2 2 2
alumina column (CH Cl ) to give a 76% yield of L as a red viscous
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Journal Name
-1
product; Rf = 0.72 (CH Cl / alumina); IR (KBr, cm ): ν (C=N) = 1555; were tested and evaluated by batch method. The adsorption
2
2
1
ν (C=C) = 1454; H NMR (DMSO-d6): δ 4.79 (s, 1H, CH
2
); 7.43 (t, 1H, properties of (SiNPr2) for Pb(II), Zn(II), Cu(II) and Cd(II) have been
Py-Hβ); 7.60 (d, 1H, Py-Hδ); 824 (t, 1H, Py-Hγ); 8.37 (d, 1H, Py-Hᾳ); investigated. After the extraction, the suspension was separated;
1
3
C NMR (DMSO-d6): δ 56.08 (1C, CH
2 β
); 124.21 (1C, Py-C ); 125.60 the residual metal concentration was determined by FAAS using
(
1C, Py-C ) 145.45 (1C, Py-Cγ); 146.70 (1C, Py-Cᾳ); 149.02 (1C, Py- standard solutions for calibration.
δ
+
Cε); MS: m/z, 129.63 (M+2) .(32.45%).
Acknowledgements
2
Synthesis of 3-aminopropylsilica (SiNH ): 25 g of activated silica gel
The authors extend their appreciation to the PPR2-MESRSFC-
CNRST-P10 project (Morocco). Sincere appreciation was also
extended to the Deanship of Scientific Research at King Saud
University for its supporting this Prolific Research group (PRG-1437-
was dispersed into dried toluene (150 mL) in a necked flask,
refluxed and mechanically stirred under N (g) atmosphere for 2h,
2
and then 3-aminopropyltrimethoxysilane (10 mL) was gradually
added into the solution with continuous stirring. The mixture was
refluxed for 24h. The final product was filtered, washed with
toluene and ethanol. It was then Soxhlet extracted with a mixture
of ethanol and dichloromethane (1/1) for 12h, to remove the
silylating reagent residue. The immobilized silica gel was dried in
vacuum at room temperature. Elemental analyses: %C = 4.46; %N =
2
9).
References
1
2
3
L. Carro, V. Anagnostopoulos, P. Lodeiro, J.L. Barriad, R. Herrero
and M.E.S. Vicente, Bioresource Technol. 2010, 101, 8969-8974.
J.X. Wang, X.B. Feng, C.W.N. Anderson, Y. Xing and L.H. Shang, J.
Hazard. Mater. 2012, 221-222, 1-18.
1.66.
J.E. Fergusson, editor. The Heavy Elements: Chemistry,
Environmental Impact and Health Effects. Oxford: Pergamon
Press; 1990.
Synthesis of bipyridine tripodal-substituted (SiNPr ): For the
2
2 2
synthesis of SiNPr , the mixture of 3-aminopropylsilica (SiNH ) (4g),
L2 (6.75g, 52.91 mmol) and sodium carbonate (8.41 g, 79.36 mmol)
were reacted in 150 mL of dry acetonitrile. The reaction was stirred
and refluxed under nitrogen for 6 days. Then the substituted silica
was filtered off and washed with hot water to dissolve sodium
carbonate. The product was transferred to the Soxhlet extraction
apparatus for reflux-extraction in acetonitrile, methanol and
dichloromethane for 12h, respectively. The product was dried
under vacuum at 70°C over 24h.
4
5
H. Bradl, editor. Heavy Metals in the Environment: Origin,
Interaction and Remediation, Volume 6. London: Academic
Press; 2002.
P.B. Tchounwou, C.G. Yedjou, A.K. Patlolla and D.J. Sutton,
Heavy Metal Toxicity and the Environment, Volume 101.
Experientia Supplementum, 2012; pp. 133–164.
6
7
A.A. Khan and L. Paquiza, Desalination, 2011, 265, 242-254.
F.N. Liu, G.L. Zhang, Q. Meng and H.Z. Zhang, Chin. J. Chem. Eng.
Heavy metal adsorption experiments
2
008, 16, 441-454.
In order to test the metal adsorption ability of the synthesized
materials, a set of adsorption experiments was carried out by
stirring 10 mg of functionalized silica in 10 mL of a single metal
solution at 25°C. The aqueous systems selected were Pb(II), Zn(II),
Cu(II) and Cd(II) with optimum concentration. The pH values were
8
9
W.S. Ngah, L.C. Teong and M.A.K.M. Hanafiah, A review,
Carbohyd. Polym. 2011, 83, 1446-1456.
A. Afkhami, M. Saber-Tehrani and H. Begheri, J. Hazard. Mater.
2
010, 181, 836-844.
adjusted with dilute hydrochloric acid and sodium hydroxide 10 H. Sakai, S. Matsuoka, A.A. Zinchenko and S. Murata, Colloid.
solution. After shaken for 1h, Adsorbent-solution mixtures were
Surf. A. 2009, 347, 210-214.
filtered to collect the final solutions. Metal concentrations, both in 11 S.K. Nataraj, K.M. Hosamani and T.M. Aminabhavi, Desalination,
the initial and final solution, were determined by a FAAS. The
2
009, 249, 12-17.
equilibrium adsorption capacity of adsorbent was calculated by the
1
1
1
1
1
1
2
3
4
5
6
7
F. Ke, L.G. Qiu, Y.P. Yuan, F.M. Peng, X. Jiang, A.J. Xie, Y.H. Shen
and J.F Zhu, J. Hazard. Mater. 2011, 196, 36-43.
4
4
following equations
:
F. Di Natale, A. Erto, A. Lancia and D. Musmarra, J. Hazard.
Mater. 2011, 192, 1842-1850.
Q
M
= (C
0
− Ce) × V / W (8)
T. Phothitontimongkol, N. Siebers, N. Sukpirom and F. Unob,
Appl. Clay. Sci. 2009, 43, 343-349.
Q
W
= Q × M (9)
M
where Q
M
is the amount of the metal ion on the adsorbent
mmol/g), Q is the amount of the metal ion on the adsorbent
mg/g), V is the volume of the aqueous solution (L), W is the weight
the initial concentration of metal ion
the equilibrium metal ion concentration in solution
mmol/L) and M the atomic weight for metals (g/mol).
R.J. Qu, C.M. Sun, Y. Zhang, J. Chen, C.H. Wang, C.N. Ji and X.G.
Liu, J. Chem. Eng. Data, 2010, 55, 4343-4351.
(
(
W
Y.M. Zhou, X.Y. Hu, M. Zhang, X.F. Zhuo and J.Y. Niu, Ind. Eng.
Chem. Res. 2013, 52, 867-884.
of the adsorbent (g), C
0
(mmol/L), C
e
X.Y. Zhang, Q.C. Wang, S.Q. Zhang, X.J. Sun and Z.S. Zhang, J.
Hazard. Mater. 2009, 168, 1575-1580.
(
For each set of data present, standard statistical methods were
used to determine the mean values and standard deviations.
Confidence intervals of 95% were calculated for each set of samples
in order to determine the margin error.
1
1
8
9
S L. Mercier, J. Mater. Chem. A, 2010, 20, 4478–4511.
C.A. Quirarte-Escalante, V. Soto, W.D.L Cruz, G.R. Porras, R.
Manríquez and S. Gomez-Salazar, Chem. Mater. 2009, 21, 1439–
1
450.
H.-T. Fan, Q. Tang, Y. Sun, Z.-G. Zhang and W.-X. Li, Chem. Eng. J.
014, 258, 146–156.
Batch experiments
2
2
0
1
2
The effect of pH, time of contact, concentration, kinetics,
temperature of the system and competitive extraction of metals
S. A. El-Safty and T. Hanaoka, Chem. Mater., 2004, 16, 384–400.
8
| J. Name., 2016, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 9 of 10
Journal Name
View Article Online
DOI: 10.1039/C6RA14349K
ARTICLE
2
2
H.-T. Fan, Y. Sun, Q. Tang, W.-L. Li and T. Sun, J. Taiwan Inst. 47 G.Z. Fang, J. Tan and X.P. Yan, Anal. Chem. 2005, 77, 1734-1739.
Chem. Eng. 2014, 45, 2640–2648.
48 M. Najafi, Y. Yousefi and A.A. Rafati, Sep. Purif. Technol. 2012,
85, 193-205.
2
2
3
4
J. Hu, L. Liu and Z. Xiao, RSC Adv., 2015, 5, 68092–68098.
L. Wang, C. Cheng, T. Sen, J. Lei, M. Matsuoka, J. Zhang and F. 49 P. Roumeliotis, A.A. Kurganov and V.A. Davankov, J.
Zhang, J. Mater. Chem. A, 2015, 3, 13357-13364. Chromatogr. A. 1983, 266, 439-450.
H.-T. Fan, W. Sun, B. Jiang, Q.-J. Wang, D.-W. Li, C.-C. Huang, K.- 50 G.V. Kudryavtsev, D.V. Milchenko, S.Z. Bernadyuk, T.E
2
5
J. Wang, Z.-G. Zhang and W.-X. Li, Chem. Eng. J. 2016, 286, 128–
38.
Vertinskaya and G.V. Lisichkin, Theor. Exp. Chem. USSR 1988,
23, 658-663.
1
2
2
2
2
6
7
8
9
H.-T. Fan, J.-X. Liu, H. Yao, Z.-G. Zhang, F. Yan and W.-X. Li, Ind. 51 J.X. Yu, L.Y. Wng, R.A. Chi, Y.E. Zhang, Z.G. Xu and J. Guo, Appl.
Eng. Chem. Res. 2014, 53, 369–378. Surf. Sci. 2013, 268, 163-170.
X. Zheng, C. Wang, J. Dai, W. Shi and Y. Yan, J. Mater. Chem. A, 52 B.K. Nandi, A. Goswami and M.K. Purkait, J. Hazard. Mater.
015, 3, 10327-10335. 2009, 161, 387–395.
J. Hu, X. Wang, L. Liu and L. Wu, J. Mater. Chem. A., 2014, 2, 53 A. Shahbazi, H. Younesi and A. Badiei, Chem. Eng. J. 2011, 168,
9771-19777. 505-518.
(a) S. Radi, Y. Toubi, M. Bacquet, S. Degoutin, Y. N. Mabkhot 54 J. Febrianto, A.N. Kosasih, J. Sunarso, Y.H. Ju, N. Indraswati and
and Y. Garcia, RSC Adv., 2016, 6, 34212–34218. (b) S. Radi, S. S. Ismadji, J. Hazard. Mater. 2009, 162, 616-645.
Tighadouini, M. Bacquet, and M. Zaghrioui, J. Sulfur Chem., 55 L.M. Zhou, J.H. Liu and Z.R. Liu, J. Hazard. Mater. 2009, 172,
016, 37, 296-306. (c) S. Radi, A. Attayibat, M. El Massaoudi, M. 439-446.
Bacquet, S. Jodeh, I. Warad, S. S. Al-Showiman and Y. N. 56 M.F. Sawalha, J.R. Peralta-Videa and J. Romero-Gonzales, J.
Mabkhot, Talanta, 2015, 143, 1-6. (d) S. Tighadouini, S. Radi, M. Colloid. Interf. Sci. 2006, 300, 100-104.
2
1
2
Bacquet, J.P. Dacquin. Y.N. Mabkhot, S. Jodeh, I. Warad and M. 57 I. Langmuir, J. Am. Chem. Soc. 1916, 38, 2221-2295.
Zaghrioui, Sep. Sci. Technol., 2015, 50, 710-717. (e) S. Radi, S. 58 H.M.F. Freundlich, Z. Phys. Chem. 1906, 57, 385-470.
Tighadouini, M. El Massaoudi, M. Bacquet, S. Degoutin, B. Revel 59 A. Sari, M. Tuzen, Ö.D Uluözlü and M. Soylak, Biochem. Eng. J.
and Y. N. Mabkhot, J. Chem. Eng. Data, 2015, 60, 2915-2925.
2007, 37, 151-158.
3
0
S. Parambadath, A. Mathew, S.S. Park and C.S. Ha, J. Environ. 60 F. Xie, X. Lin, W. Wu and Z. Xie, Talanta 2008, 74, 836–843.
Chem. Eng., 2015, 3, 1918-1927.
61 X. Huang, X. Chang, Q. He, Y. Cui, Y. Zhai and N. Jiang, J. Hazard.
Mater. 2008, 157, 154–160.
3
3
1
2
S. A. Ahmed, J. Environ. Chem. Eng., 2014, 2, 1713-1721.
M. Li, M.Y. Li, C.G. Feng and Q.X. Zeng, Appl. Surf. Sci., 2014, 62 A. Shahbazi, H. Younesi and A. Badiei, Chem. Eng. J. 2011, 168,
14, 1063-1069. 505–518.
Z. Ezzedine, I. Batonneau-Gener, Y. Pouilloux, H. Pouilloux, H. 63 H.-T. Fan, X.-T. Sun, Z.-G. Zhang, and W.-X. Li, J. Chem. Eng. Data
3
3
3
Hamad, Z. Saad and V. Kazpard, Micropor. Mesopor. Mat., 2015,
12, 125-136.
2014, 59, 2106−2114.
2
64 S. He, C. Zhao, P. Yao and S. Yang, Des. Water Trait. 2016, 57,
3
3
3
3
3
4
5
6
7
8
Y. Niu, R. Qui, H. Chen, L.Mu, X. Liu, T. Wang, Y. Zhang and C.
Sun, J. Hazard. Mater. 2014, 278, 267-278.
1722−1732.
P. Wang, M. Du, H. Zhu, S. Bao, T. Yang and M. Zou, J. Hazard.
Mater. 2015, 186, 533-544.
S. Radi, S. Tighadouini, Y. Toubi and M. Bacquet, J. Hazard.
Mater. 2011, 185, 494-501.
M.A. Esteves, A. Cachud, S. Chaves and M.A. Santos, J. Inorg.
Biochem. 2005, 99, 1762-1768.
E.G. Vieira, I.V. Soares, N.L. Dias Filho, N.C. da Silva, E.F. Garcia,
A.C. Bastos, S.D. Perujo, T.T. Ferreira, A.H. Rosa and L.F. Fraceto,
J. Colloid Interface Sci. 2013, 391, 116-124.
3
9
S. Radi, S. Tighadouini, M. Bacquet, S. Degoutin, B. Revel and M.
Zaghrioui, J. Environ. Chem. Eng., 2015, 3, 1769-1778.
S. Watanesk and A.A. Schilt, Talanta, 1986, 33, 895-899.
Y.Y. Hui, H.H. Shu, H.M. Hu, J. Song, H.L. Yao and X.L. Yang,
Inorg. Chimi, Acta. 2010, 82, 3238-3243.
4
4
0
1
4
4
2
3
M.M. Matlock, B.S. Howerton, K.R. Henke and D.A.A. Atwood, J.
Hazard. Mater. 2001, 82, 55-63.
T. Kawato. H. Koyama, H. Kanatomi and Y. Muramoto, Inorg.
Chim. Acta. 1991, 183, 107-112.
4
4
4
5
X. Xue and F. Li, Micropor. Mesopor. Mater. 2008, 116, 116-122.
J.A.A. Sales, F.P. Faria, A.G.S. Prado and C. Airoldi, Polyhedron
2004, 23, 719-725.
4
6
Y. Liu, Z. Liu, J. Gao, J. Dai, J. Han, Y. Xang, J. Xie and Y. Yan, J.
Hazard. Mater. 2011, 186, 197-205.
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DOI: 10.1039/C6RA14349K