Shape-selective production of zinc phosphate in aqueous and nonaqueous media using (2-hydroxyethyl) trimethylammonium hydroxide-assisted sonochemical route

Article abstract of DOI:10.1007/s13738-011-0053-4

Zinc phosphatemolecular sieveswere synthesized using zinc chloride, phosphoric acid and (2-hydroxyethyl) trimethylammonium hydroxide as template, respectively. Synthesized samples were characterized by XRD, SEM and FT-IR techniques. The morphology and crystal size of the samples were investigated using ultrasonic during aging process. Large particle size (7.2 × 20.4 μm) was obtained by ultrasonication. Imperfect orthorhombic particles were obtained when the sample was mixed with magnetic stirrer; meanwhile, some rod-like particles were obtained when the mixture was stirred with ultrasonic. In addition, the rod-like b-Zn₃(PO₄)₂· 4H₂O phase was prepared using ethylene glycol as co-solvent. Iranian Chemical Society 2012.

Full text of DOI:10.1007/s13738-011-0053-4

J IRAN CHEM SOC (2012) 9:431–439
DOI 10.1007/s13738-011-0053-4
ORIGINAL PAPER
Shape-selective production of zinc phosphate in aqueous
and nonaqueous media using (2-hydroxyethyl)
trimethylammonium hydroxide-assisted sonochemical route
•
Abdolraouf Samadi-Maybodi
Seyed Karim Hassani Nejad-Darzi
Received: 26 May 2011 / Accepted: 5 August 2011 / Published online: 10 January 2012
Ó Iranian Chemical Society 2012
Abstract Zincphosphatemolecularsievesweresynthesized
using zinc chloride, phosphoric acid and (2-hydroxyethyl)
trimethylammonium hydroxide as template, respectively.
Synthesized samples were characterized by XRD, SEM and
FT-IR techniques. The morphology and crystal size of the
samples were investigated using ultrasonic during aging pro-
cess. Large particle size (7.2 9 20.4 lm) was obtained by
ultrasonication. Imperfect orthorhombic particles were
obtained when the sample was mixed with magnetic stirrer;
meanwhile, some rod-like particles were obtained when the
mixture was stirred with ultrasonic. In addition, the rod-like
b-Zn3(PO4)2Á4H2O phase was prepared using ethylene glycol
as co-solvent.
phosphates materials show structures similar to zeolites and
exhibit the same topologies of aluminosilicates [7]. Zinc
phosphates have found wide applications, such as ion
exchange materials, chelating agents, corrosion-resistant
coatings, glass ceramics, biomedical cements, and high
quality fertilizers [8–11]. The most frequent applications of
zinc phosphates were as pigments for coating products (iron
and steel alloys), which possess very good anticorrosive
properties and are nontoxic substances [12, 13]. Especially,
nowadays these materials have been used in electric motors
and transformers and in the automotive industry [14].
Zn3(PO4)2Á4H2O, one of the important zinc phosphates, has
found widespread application as mentioned above [8].
A generic approach based on the basic principles of bio-
mineralization has been applied to the synthesis of zinc
phosphate nanoparticlesbychemicalprecipitation using yeast
cells[15].Openframeworkphosphatesaregenerallyprepared
by employing hydro/solvothermal methods in the presence of
an organic amine. The amine molecule generally occupies
cavities and channels and in some cases can be removed by
post-synthesis treatments, such as calcination, acid leaching,
etc. [1]. Templates are usually incorporated into pores or
cavities of anionic zinc phosphate frameworks in their pro-
tonated forms [7]. Shape-selective fabrication of zinc phos-
phate hexagonal bipyramids via a disodium phosphate with
ultrasonic were selectively synthesized by Jung et al. [16].
Sonochemistry is related to the use of power ultrasound
to enhance chemical reactivity in a liquid medium.
Applying ultrasound was shown to provide significant
changes in the rates, yields and product properties of sev-
eral processes [17]. The sonochemistry is the research area
in which molecules undergo a chemical reaction due to the
application of ultrasound radiation (20 kHz–10 MHz).
Ultrasound can improve and change dissolution processes,
chemical reactions, nucleation and growth of particles [18].
Keywords Zinc phosphate Á (2-Hydroxyethyl)
trimethylammonium Á Ethylene glycol Á Ultrasonic
Introduction
Research in the area of solids with open framework is inter-
esting for many potential applications, such as catalysis,
sorption, and separation processes [1, 2]. Zinc phosphates
with open architectures are interesting due to the fact that the
total charges associated with them (?2 and ?5) are similar to
those of the aluminosilicates (?3 and ?4) [3–6]. Zinc
A. Samadi-Maybodi (&) Á S. K. H. Nejad-Darzi
Analytical Division, Faculty of Chemistry,
University of Mazandaran, P.O. Box 47416-95447,
Babolsar, Iran
e-mail: samadi@umz.ac.ir
Present Address:
S. K. H. Nejad-Darzi
Faculty of Basic Science, Babol Noshirvani University
of Technology, P.O. Box 47148-71167, Babol, Iran
123

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J IRAN CHEM SOC (2012) 9:431–439
Application of ultrasound clearly offers potential for effect
on the hydrothermal crystallization process and some of the
final properties and shape of the synthetic zeolite samples.
The most important result of using sonication in the syn-
thesis of zeolite has been shown previously for the prepa-
ration of aluminosilicate zeolites [19–26].
used without further purification. Ortho-phosphoric acid
(85% wt) and Amberlite resin CG-400 (OH) were pur-
chased from Fluka company. Double distilled water was
used throughout. The 2-HETMACl was converted to its
hydroxide forms by dissolving it in minimum amount of
water and passing it down from a column of Amberlite
resin CG-400 (OH).
Polyethylene glycol (pEG) is an important precursor for the
preparation of many surfactants, which has good emulsifica-
tion and lubrication ability. Tian et al. [27] has investigated the
effect of pEG molecules on the growth of Me-AlPO4-5 crys-
tals. The volume ratio of pEG:H2O in the reaction mixtures
has significant influence on the morphology of the synthesized
crystals. This new synthetic strategy may be applied to the
control of the crystal morphology of other zeolites and related
materials, such as phosphate-based molecular sieves.
Synthetic procedure
Zinc phosphate molecular sieves were synthesized using
zinc chloride and phosphoric acid as zinc and phosphor
source, respectively. A mixture containing zinc, phos-
phorous, (2-hydroxyethyl) trimethylammonium hydroxide
(2-HETMAOH) and deionized water was prepared with
the molar ratio of Zn:3 H3PO4:4.2 (2-HETMAOH):250
H2O. In a typical synthesis, ZnCl2Á6H2O was first dis-
solved in water with stirring, followed by successive
addition of H3PO4 and 2-HETMAOH. A white precipitate
was formed during the addition of the 2-HETMAOH,
followed by stirring for 30 min at ambient temperature
(ca. 22 °C). The reaction mixture was subjected to
microwave oven at low power (e.g. 100 W) for 1 h. The
reactants were transferred in a 60 mL Teflon lined stain-
less steel autoclave and heated at 180 °C under static
conditions for appropriate times. The colorless crystals
were filtered, washed several times with distilled water
and dried at 90 °C overnight. It is pertinent to point out
that the pH of the mixture was decreased from 8 to 6
during the synthesis processing. The compositions and
synthesis conditions are presented in Table 1.
To the best of our knowledge, no new topology of the
zinc phosphate molecular sieves has been synthesized
using a (2-hydroxyethyl) trimethylammonium hydroxide
(2-HETMAOH) as template. In this work, crystallization of
the zinc phosphate with conventional hydrothermal (CH)
method and microwave assisted hydrothermal (MAH)
method has been investigated using above template. The
effects of the stirring aging and ultrasonic-assisted aging
were investigated on the crystallization of zinc phosphate
before heat treatment. In addition, the effect of EG on the
crystal’s shape of zinc phosphate was investigated. Zeolites
were characterized by XRD, SEM and FT-IR techniques.
Experimental
Materials
Apparatus and characterization
Zinc chloride (ZnCl2), 2-hydroxyethyl trimethylammoni-
um chloride (2-HETMACl), sodium hydroxide and ethyl-
ene glycol (EG) were obtained from Merck company and
XRD patterns were recorded by an X-ray diffractometer
(XRD, GBC–MMA Instrument) with Be Filtered Cu Ka
Table 1 Synthetic conditions such as method and time of heating and composition of as-synthesized zinc phosphate molecular sieves listed in
this study
Sample no.
Composition of reactant (mole ratio)
MW time (h)
CH time (h)
Method of aging
ZP1a
ZP2
ZP3
ZP4
ZP5
ZP6
ZP7
ZP8
ZP9
ZP10
Zn:3 H3PO4:4.2 (2-HETMAOH):250 H2O
0.0
0.0
1.0
1.0
1.0
0.0
0.0
0.0
0.0
0.0
72.0
72.0
48.0
48.0
48.0
48.0
72.0
72.0
72.0
72.0
Stirring aging
Zn:3 H3PO4:4.2 (2-HETMAOH):250 H2O
Ultrasonic-assisted
Stirring aging
Zn:3 H3PO4:4.2 (2-HETMAOH):250 H2O
Zn:3 H3PO4:4.2 (2-HETMAOH):250 H2O
Ultrasonic-assisted
Stirring aging
Zn:2.6 H3PO4:3.7 (2-HETMAOH):17.7 EG:225 H2O
Zn:2.6 H3PO4:3.7 (2-HETMAOH):17.7 EG:225 H2O
Zn:2.6 H3PO4:3.7 (2-HETMAOH):17.7 EG:225 H2O
Zn:2.6 H3PO4:3.7 (2-HETMAOH):17.7 EG:225 H2O
Zn:2.6 H3PO4:3.7 (2-HETMAOH):22.1 EG:208.3 H2O
Zn:2.6 H3PO4:3.7 (2-HETMAOH):29.4 EG:185.4 H2O
Stirring aging
Stirring aging
Ultrasonic-assisted
Ultrasonic-assisted
Ultrasonic-assisted
MW microwave, CH conventional hydrothermal
a
Samples ZP1–ZP4 were heated at 180 °C and samples ZP5–ZP10 were heated at 160 °C
123

J IRAN CHEM SOC (2012) 9:431–439
433
˚
radiation (1.5418 A) operating at 35.4 kV and 28 mA. The
scanning range of 2h was set between 28 and 508 with scan
rate of 0.05 degree/s. Scanning electron microscopy (SEM,
VEGA2–TESCAN) was employed to study morphology
and size of obtained crystals.
A microwave oven
(2.45 GHz, 100 W) was used as a part of synthesis pro-
cessing. It should be mentioned that for avoiding of water
evaporation, the solution was refluxed during microwave
irradiation. IR spectra were obtained by a Bruker FT-IR
spectrometer (Vector 22).
Results and discussion
Synthesis of zinc phosphate in aqueous media
Four different procedures were applied for synthesis of zinc
phosphate molecular sieves in aqueous media: (1) mixing
by stirring aging (sample ZP1), (2) mixing with ultrasonic-
assisted aging (sample ZP2) which those heated with
conventional hydrothermal method (72.0 h at 180 °C), (3)
mixing by stirring aging (sample ZP3) and (4) mixing with
ultrasonic-assisted aging (sample ZP4) that those irradiated
by microwave (1 h) and heated by hydrothermal (48.0 h at
180 °C). The conditions for synthesis of the samples are
presented in Table 1.
Fig. 2 FT-IR spectra of zinc phosphate molecular sieves in aqueous
media: a sample ZP1, b sample ZP2, c sample ZP3 and d sample ZP4.
The synthesis conditions are presented in Fig. 1
XRD patterns of the above samples are shown in
Fig. 1a–d. As shown in Fig. 1a and b, for samples ZP1 and
ZP2 respectively, two kinds of as-prepared zinc phosphate
have similar XRD patterns, except for relative peak
intensities which can be related to the random orientation.
The XRD analyses confirmed that as-prepared zinc phos-
phate with or without ultrasonication correspond to the
same phase because there is no diffraction peak observed
due to impurities in the XRD patterns. However, there is
moderate difference between XRD patterns of samples ZP3
and ZP4 (Fig. 1c, d). As a result, the crystal structure can
be influenced by microwave irradiation.
Fig. 1 Representation XRD
pattern of zinc phosphate
molecular sieves in aqueous
media without MW and with
CH of 72.0 h at 180 °C: a ZP1
with stirring aging, b ZP2 with
ultrasonic-assisted aging and
with MW of 1.0 h and CH of
48.0 h, c ZP3 with stirring aging
and d ZP4 with ultrasonic-
assisted aging
123

434
J IRAN CHEM SOC (2012) 9:431–439
Fig. 3 Representative SEM
images of zinc phosphate
molecular sieves in aqueous
media: a sample ZP1, b sample
ZP2, c sample ZP3 and
d sample ZP4. SEM
magnification is 5,000. The
synthesis conditions are
presented in Fig. 1
Fig. 4 XRD pattern of zinc
phosphate molecular sieves in
EG:H2O (1:4, v/v) with stirring
aging at 160 °C: a ZP5 with
MW of 1.0 h and CH of 48.0 h,
b ZP6 without MW and CH of
48.0 h and c ZP7 without MW
and CH of 72.0 h
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J IRAN CHEM SOC (2012) 9:431–439
435
Figure 2 shows FT-IR spectra of as-synthesized zinc
phosphate (samples ZP1–ZP4) in aqueous media with dif-
ferent conditions. Two strong broad bands at 3,400–
Table 2 Powder XRD data for b-Zn3(PO4)2.4H2O (b-Hopeite)
h
k
l
dcalc
˚
(A)
Int.
h
k
l
dcalc
˚
(A)
Int.
3,700 cm-1 and1,600–1,700 cm-1 (centeredat 1,640 cm-1
)
0
2
2
0
0
1
1
2
0
2
1
2
2
1
2
0
2
0
3
2
3
4
3
2
4
1
0
1
3
1
0
2
0
0
1
3
1
2
0
4
1
4
2
2
3
2
0
1
1
4
1
2
3
3
0
3
4
2
4
3
6
5
5
1
4
2
0
3
5
2
6
0
0
4
1
2
6
7
8
3
5
7
2
4
3
4
5
3
8
6
0
0
0
1
0
1
1
0
1
1
1
0
1
1
1
0
0
1
1
1
1
0
1
1
0
1
2
2
1
2
2
1
1
0
2
1
1
2
2
1
2
0
2
0
1
9.1600
5.3110
5.0950
4.8550
4.5760
4.4140
4.0720
4.0050
3.8800
3.6480
3.6480
3.4680
3.3910
3.2250
3.1340
3.0530
3.0150
2.9630
55
17
25
30
55
35
7
3
2
4
3
4
3
2
5
2
3
4
5
4
5
4
3
2
6
2
5
3
4
1
3
2
1
0
4
3
5
2
6
2
5
6
1
6
5
0
0
2
3
2
1
4
1
4
6
2
5
7
8
2
9
4
7
3
0
4
2
5
9
2
2
2
0
2
1
1
1
1
0
2
0
1
2
1
2
2
1
0
0
1
2
2
2
1
1
3
3
0
2
2
3
0
3
2
1
1
0
2
0
3
2
3
3
3
0
2.0380
2.0380
3
3
are denoted to the stretching and bending vibration of water
molecules adsorbed on OH groups, respectively [16, 28–30].
The broad bands shown at 900–1,300 cm-1 (peak at
1,033 cm-1) and 500–700 cm-1 were attributed to the
2.0020 16
2.0020 16
3-
1.9770
2
complex stretching and bending vibrations of the PO4
1.9400 25
1.9400 25
group, respectively [11, 16]. The bands at region of
1,000–1,250 cm-1 belong to the asymmetric stretch of TO4
tetrahedra and were characteristic of all zeolites and zeolite
like materials [22]. There are some differences among the IR
spectra of the corresponding samples. As clearly observed,
the band located at 3,570 cm-1 for the samples ZP1 and ZP2
is more intense than that of samples ZP3 and ZP4. Never-
theless, the band positioned at 1,600 cm-1 for the samples
ZP3 and ZP4 was not detectable. As a consequence, the route
of synthesis can be affected by adsorbed water on the final
product.
20
14
9
1.9111
1.8994
1.8715
1.8618
1.8618
2
1
1
2
2
9
30
40
1
1.8247 15
1.7985
1.7896
1.7896
1.7772
1.7361
1.7306
1.7252
1.7014
1.6953
1.6719
1.6646
1.6370
1.6298
1.6169
1.6143
1.6143
1.5974
1.5931
1.5931
1.5755
1
1
1
3
5
4
3
2
6
6
5
5
3
3
4
4
4
4
4
1
9
1
The SEM images of the above samples are illustrated in
Fig. 3a–d. The results indicated that atypical particles with
small amounts of imperfect orthorhombic shape were
produced using magnetic stirrer. The results obtained from
SEM images of the samples ZP1 and ZP2 indicated that
crystal growth is highly improved by application of ultra-
sonic. Average particle size of the crystals was increased
from 4.4 9 11.8 to 7.2 9 20.4 lm by ultrasonication.
Ultrasound is known to result in acoustic streaming pro-
viding enhanced mass transfer close to the crystal surface
which is expected to increase the crystal growth rate [25].
However, increasing in the nucleation rate in the presence
of ultrasound may also cause increase in the crystallization
rate; nonetheless, crystal growth is generally dominant in
this process.
4
8
2.8550 100
2.8550 100
10
5
2.7600
2.6520
2.6140
2.5850
2.5480
2.5350
2.5150
2.4450
2.4450
2.4260
2.4260
2.3420
2.3210
2.2880
2.2710
2.2710
2.2680
2.2060
2.2060
2.1900
2.1580
2.1480
2.1300
2.1000
2.1000
3
19
25
3
6
4
8
9
15
11
15
3
10
2
3
9
3
7
10
10
7
2
1
By comparison of Fig. 3a and c, it can be said that
crystal size of the sample is affected by microwave irra-
diation. In conventional heating, heat is transferred to the
material by convection and conduction. Here, the sample is
heated relatively slow and due to a temperature gradient
and consequently it can be expected to obtain samples with
less uniform crystals (e.g. sample ZP1). In sample ZP3
with MW heating, the oscillating electromagnetic field
‘‘generated by microwaves’’ interacts with the dielectric
properties of materials resulting in the rotation of molec-
ular dipoles and therefore, energy dissipates as heat from
internal resistance to that rotation [31]. In this case, the
sample is heated very rapidly and hence particle size of the
sample is reduced. Obtained results from SEM photographs
specify that the sample ZP4 has larger particle size than
5
1
2
7
3
1.5672 10
1.5672 10
15
15
13
4
4
11
6
1.5633
1.5295
1.5295
9
9
9
4
4
12
5
1.5254 10
1.5254 10
2
7
9
1.5161
1.5161
3
3
3
0
1
4
1.5092 10
1.5092 10
11
11
5
10
1.5068
7
123

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J IRAN CHEM SOC (2012) 9:431–439
Table 3 Crystal data and structure refinement parameters for b-Zn3(PO4)2.4H2O (b-Hopeite)
3
Cell volume (A )
Formula weight (g mol-1
)
Space group
Pnma (62)
dcalc (g cm-3
)
˚
a (A)
˚
b (A)
˚
c (A)
˚
458.14
10.611
18.312
5.0309
977.55
3.113
stirring aging at 160 °C with different circumstances: (1)
with MW irradiation of 1.0 h and CH of 48.0 h (sample
ZP5); (2) with CH of 48.0 h without MW irradiation
(sample ZP6) and (3) CH of 72.0 h without MW irradiation
(sample ZP7). On the basis of literature [15, 32], XRD
patterns that are shown in Fig. 4 can be ascribed to the
lattice of b-Zn3(PO4)2Á4H2O. As can be seen, XRD patterns
contain narrow and high intensity peaks indicating the
prepared samples have small size as well as excellent
crystallinity. It is pertinent to point out that a small
impurity was observed in sample ZP6 which pronounces
CH time of 48.0 h without MW is not enough for prepa-
ration of pure b-Zn3(PO4)2Á4H2O crystals. The crystal
structure data of this phase obtained by XRD are summa-
rized in Table 2. Powder X-ray diffraction data for
b-Zn3(PO4)2Á4H2O including miller indices and d-space are
listed in Table 3.
Figure 5 displays FT-IR spectra of as-synthesized zinc
phosphate in the mixture of EG:H2O (1:4, v/v) with different
experimental conditions. Two strong broad bands at
3,400–3,700 cm-1 and 1,600–1,700 cm-1 (centered at
1,640 cm-1) are denoted to the stretching and bending
vibration of water molecules adsorbed on OH groups,
respectively [16, 28–30]. The broad bands shown at 900–
1,300 cm-1 (peak centered at 1,030 cm-1) and 500–
700 cm-1 were attributed to the complex stretching and
bending vibrations of the PO43- group, respectively [11, 16].
As can be seen in Fig. 5, the features of the FT-IR spectra
for all three samples are the same, which means that all
above samples have similar phase. However, transmit-
tance percentage (T%) for the corresponding samples is
different. The same results were obtained in XRD pat-
terns, i.e., no significant difference are observed among
the XRD data. It is noticeable that all three XRD patterns
(Fig. 4) are the same and also the FT-IR spectra (Fig. 5)
are similar. This fact indicates a good agreement between
the XRD and FT-IR results. The FT-IR spectra of the
samples ZP5–ZP7 shown in Fig. 5 are different from the
FT-IR spectra of the samples ZP1–ZP4 in Fig. 2. Similar
observations hold for the XRD patterns of the corre-
sponding samples.
Fig. 5 FT-IR spectra of zinc phosphate molecular sieves in EG:H2O
(1:4, v/v) with stirring aging at 160 °C: a sample ZP5, b sample ZP6
and c sample ZP7. The synthesis conditions are presented in Fig. 4
sample ZP3 (see Fig. 3c, d). It is accepted that the ultra-
sound causes increasing crystal growth and consequently
obtaining larger particles. As can be seen in Fig. 3d, some
rod-like particles are obtained when the precursor solution
was stirred with ultrasonic and heated by microwave-
assisted hydrothermal method. The results obtained from
XRD, FT-IR and SEM analysis (Figs. 1, 2, 3) specified that
the phases of the synthesized compounds are not the
favorite phase (i.e., b-Zn3(PO4)2Á4H2O). Hence, we deci-
ded to use a mixture of water and ethylene glycol as a
solvent.
It is pertinent to point out that samples ZP5–ZP7 have
similar XRD patterns with sample ZP8 except for relative
peak intensities which can be related to the random ori-
entation. Hence, the SEM images of the samples ZP5–ZP7
resemble the SEM image of sample ZP8 (see following
section).
Synthesis of zinc phosphate in nonaqueous media
Synthesis in ethylene glycol/H2O mixture
Three kinds of zinc phosphate molecular sieves were
synthesized in ethylene glycol (EG)/H2O (1:4, v/v) with
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J IRAN CHEM SOC (2012) 9:431–439
437
Fig. 6 XRD pattern of zinc
phosphate molecular sieves with
ultrasonic-assisted aging and
CH of 72.0 h at 160 °C with
different volume ratios of
EG:H2O: a 1:4 for sample ZP8,
b 3:7 for sample ZP9 and c 2:3
for sample ZP10
effect, several samples were prepared with different vol-
ume ratios of ethylene glycol/water (EG:H2O). The XRD
patterns of as-synthesized zinc phosphate crystals, namely,
samples ZP8 (1:4, EG:H2O), ZP9 (3:7, EG:H2O) and ZP10
(2:3, EG:H2O) are illustrated in Fig. 6a–c, respectively.
According to Fig. 6a and b, the b-Zn3(PO4)2Á4H2O phase
was obtained at CH time of 72.0 h with ultrasonication
(i.e., ZP8 and ZP9). Comparison of Fig. 6a and b (samples
ZP8 and ZP9) reveal that two XRD patterns are the
same except the former has higher intensity than the lat-
ter. However, the XRD pattern of the sample ZP10 is
completely different (Fig. 6c). This stated that the
b-Zn3(PO4)2Á4H2O phase disappeared for a EG:H2O
volume ratio of 2:3 (ZP10).
Figure 7 exhibits FT-IR spectra of the as-synthesized
zinc phosphate with different volume ratios of EG:H2O.
Two strong broad bands at 3,400–3,700 cm-1 and
1,600–1,700 cm-1 are observed in this figure which was
explained before. The broad bands shown at 900–1,300 and
500–700 cm-1 are attributed to the complex stretching and
3-
bending vibrations of the PO4 group, respectively [11,
16]. A new strong band located at 1,480 cm-1 and a weak
band at its left hand side appeared for the sample ZP10, but
these bands are not observed for samples ZP8 and ZP9.
There is a good agreement between the results obtained
from the XRD patterns and FT-IR spectra of the corre-
sponding samples. These results are consistent with SEM
results (see below).
Fig. 7 FT-IR spectra of zinc phosphate molecular sieves in EG:H2O
solution: a sample ZP8, b sample ZP9 and c sample ZP10. The
synthesis conditions are presented in Fig. 6
Figure 8a–c, illustrates the SEM images of samples
ZP8, ZP9 and ZP10, respectively. The results revealed that
the shapes, size and morphology of zinc phosphate are
changed by variation of EG:H2O volume ratio. The rod-
like b-Zn3(PO4)2Á4H2O crystal with average size of
Effect of ethylene glycol:H2O volume ratios
It is known that the nature of solvent can influence shape,
size and morphology of the crystal [27]. To realize this
123

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J IRAN CHEM SOC (2012) 9:431–439
Fig. 8 SEM image of zinc phosphate molecular sieves in EG:H2O solution: a sample ZP8, b sample ZP9 and c sample ZP10. SEM
magnification is 10,000. The synthesis conditions are presented in Fig. 6
0.27 9 1.44 and 0.23 9 1.17 lm were obtained with
volume ratios of EG:H2O, 1:4 and 3:7, respectively
(Fig. 8a, b). The spherical particles with average diameter
of 0.95 lm were achieved with EG:H2O of 2:3 volume
ratio (Fig. 8c). Clearly, no rod-like crystals are observed in
the SEM image of sample ZP10. The results are in good
agreement with XRD patterns where no signal has
appeared at 2h equal 9.6°, 19.4° and 31.5°. Therefore,
ethylene glycol plays a role of solvent as well as co-sur-
factant during the synthesis of zinc phosphate which it
leads to produce spherical particles. It is believed that
ethylene glycol can induce a curvature in the bilayers of
this phase which leads to the formation of vesicles and
thus, to spherical zinc phosphate structures. First, this
effect was reported in the synthesis of mesostructured al-
uminophosphate materials in a tetraethylene glycol/water
medium [33–35].
b-Zn3(PO4)2Á4H2O crystals were obtained with EG:H2O
volume ratios of 1:4 and 3:7, meanwhile spherical crystals
were achieved at higher concentration of ethylene glycol.
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