One-pot synthesis of pyrano[3,2-c]quinoline-2,5-dione derivatives by Fe3O4@SiO2-SO3H as an efficient and reusable solid acid catalyst

Article abstract of DOI:10.1007/s00706-016-1788-5

Abstract: In this study, Fe₃O₄@SiO₂-SO₃H was prepared as an efficient and reusable solid acid catalyst and its catalytic activity was considered in the synthesis of pyrano[3,2-c]quinoline-2,5-dione derivatives b

Full text of DOI:10.1007/s00706-016-1788-5

Monatsh Chem
DOI 10.1007/s00706-016-1788-5
ORIGINAL PAPER
One-pot synthesis of pyrano[3,2-c]quinoline-2,5-dione derivatives
by Fe3O4@SiO2-SO3H as an efficient and reusable solid acid
catalyst
Esmayeel Abbaspour-Gilandeh1 Mehraneh Aghaei-Hashjin2
•
•
Parivash Jahanshahi3 Mir Saleh Hoseininezhad-Namin2
•
Received: 19 January 2016 / Accepted: 23 May 2016
Ó Springer-Verlag Wien 2016
Abstract In this study, Fe3O4@SiO2-SO3H was prepared
as an efficient and reusable solid acid catalyst and its cat-
alytic activity was considered in the synthesis of
pyrano[3,2-c]quinoline-2,5-dione derivatives by the three-
component reaction of 4-hydroxyquinolin-2(1H)-one,
Meldrum’s acid and arylaldehydes under thermal solvent-
free conditions at 70 °C. This catalytic system can be
reused minimally for five times without any noticeable loss
of activity. In addition, the characteristic analysis of Fe3-
O4@SiO2-SO3H, such as thermogravimetric analysis,
Fourier-transform infrared spectroscopy, vibrating sample
magnetometer, scanning electron microscope, and X-ray
diffraction was performed.
Keywords Heterogeneous catalyst Á
Pyrano[3,2-c]quinoline-2,5-dione Á
Solvent-free conditions Á Three component reaction
Introduction
Heterocyclic compounds have wide applications and their
major contribution is clearly evident among various phar-
maceutical compounds. Constructing various structures to
achieve the desired functions is among the main reasons for
the widespread use of heterocyclic compounds [1, 2].
Nitrogen-containing heterocyclic molecules due to massive
presence in the nature with regard to the provision of
appropriate biological activity are noteworthy and this has
caused scientists to consider to this part of organic chem-
ical science more [3–8].
Graphical abstract
4-Hydroxyquinolones are among quinolines, which are
highly beneficial derivatives and develop activities such as
analgesic, anti-inflammatory, and anti-allergy with respect
to the existing substituents in the structure [9–11]. These
compounds as herbicides and dyes have good performance
and are used in the synthesis of heterocyclic compounds,
for example, oxazinoquinolines, isoxazoloquinolines, and
pyranoquinolines [12–14]. Pyranoquinoline is an example
of heterocyclic compounds that studying their attributes
due to the important biological properties and various
medicinal applications is highly important. In addition to
the above-mentioned activities for the quinolones deriva-
tives, various biological activities such as antibacterial,
antifungal and anti-platelet aggregation has been also
reported on them [15–17]. Natural resources for the
preparation of these compounds are limited and in most
cases, should be handled as a difficult process for their
isolation and purification of them [18, 19]. Therefore, in
Electronic supplementary material The online version of this
article (doi:10.1007/s00706-016-1788-5) contains supplementary
material, which is available to authorized users.
& Esmayeel Abbaspour-Gilandeh
abbaspour1365@yahoo.com
1
Young Researchers and Elites Club, Ardabil Branch, Islamic
Azad University, Ardabil, Iran
2
Department of Chemistry, Payame Noor University (PNU),
Tehran, Iran
3
Young Researchers and Elites Club, Rasht Branch, Islamic
Azad University, Rasht, Iran
123

E. Abbaspour-Gilandeh et al.
order to synthesize of compounds from this group,
derivatives development and their medicinal properties
have been considered [20–23].
Magnetic nanoparticles (MNPs) have been recently
developed as an attractive candidate to support catalysts
owing to their unique properties such as easy synthesis and
functionalization, good stability, high surface area, and low
toxicity [24]. The surface functionalization of magnetic
particles has received considerable interest as a picturesque
way to bridge the gap between heterogeneous and homo-
geneous catalysis. This type of heterogeneous catalysis can
be easily extracted and recovered from the final product
using an external magnet Thus, the development of silica-
coated magnetite nanoparticles as an efficient, cheap and
eco-friendly catalyst creates a new way to introduce an
amazing efficient system to facilitate catalyst recovery in
different organic reactions [25–28].
Fig. 1 TGA curve of Fe3O4@SiO2-SO3H
Figure 2 demonstrates the FT-IR spectra of Fe3O4@
SiO2-SO3H nanoparticles. The FT-IR analysis of the
Fe3O4@ SiO2-SO3H presents the basic characteristic peaks
at 578, 1091, 795, and 463 cm-1, which were attributed to
the presence of Fe–O vibration, Si–O–Si asymmetric
stretching vibration, Si–O–Si symmetric stretching vibra-
tion, and Si–O–Si bending vibration, respectively. In
addition, the presence of O–H stretching vibration near
3381 cm-1 and O–H deformed the vibration near
1637 cm-1 were confirmed for Fe3O4@ SiO2-SO3H.
The magnetic feature of the catalyst was investigated by
vibrating-sample magnetometer (VSM). The magnetization
diagram for the bare Fe3O4, Fe3O4@SiO2, and Fe3O4@-
SiO2-SO3H nanoparticles are shown in Fig. 3. The
saturation magnetization value of Fe3O4@SiO2 and Fe3-
O4@SiO2-SO3H nanoparticles appeared to be 38.67 and
16.57 emu/g, respectively, which are much lower than the
bare Fe3O4 MNPs (61.22 emu/g) [33].
Owing to our interest in the synthesis of heterocyclic
compounds and in the performance of reactions with the
aid of catalyst [29–31], we reported our results in the
efficient and rapid synthesis of pyrano[3,2-c]quinoline-2,5-
dione derivatives using Fe3O4@SiO2-SO3H as an efficient
and reusable heterogeneous solid acid catalyst under sol-
vent-free conditions (Scheme 1).
Results and discussion
The thermogravimetric analysis (TGA) of Fe3O4@SiO2-
SO3H indicates several regions corresponding to different
weight lose ranges (Fig. 1). The first weight loss below
150 °C can be due to the loss of adsorbed solvent or
trapped water from the catalyst. The second weight loss
between 150 and 500 °C can be attributed to the loss of
SO3H groups. The occurrence of further weight losses at
the temperature higher than 600 °C was likely a conse-
quence of the decomposition of silica shell [32]. These
results demonstrate that the catalyst is stable up to
approximately 250 °C, supporting that it could be safely
applied in organic reactions at the temperatures range
70–150 °C.
The X-ray diffraction (XRD) patterns of the bare Fe3O4
and Fe3O4@ SiO2-SO3H (Fig. 4), present broad peaks 2h
from 22° to 28°, which is typical for amorphous silica [33].
Some explicit peaks at 2h values of 30.29, 35.73, 42.84,
53.65, 57.9, and 62.74° are dedicated to the (220), (311),
(400), (422), (511), and (440) planes of Fe3O4 [34, 35].
Figure 5 shows the scanning electron microscope (SEM)
images of Fe3O4@SiO2 and Fe3O4@ SiO2-SO3H
Scheme 1
123

One-pot synthesis of pyrano[3,2-c]quinoline-2,5-dione derivatives by Fe3O4@SiO2-SO3H as an…
Fig. 2 FT-IR spectra of Fe3O4@ SiO2-SO3H
Fig. 4 XRD patterns of a Fe3O4 and b Fe3O4@ SiO2-SO3H
4-chlorobenzaldehyde (3g) in the presence of Fe3O4@-
SiO2-SO3H as a model reaction. The effect of temperature,
amounts of catalyst, and reaction time were surveyed and
optimized to develop the optimum conditions for this
model reaction. For this purpose, a condensation between
4-hydroxyquinolin-2(1H)-one (1 mmol), Meldrum’s acid
(1 mmol), and 4-chlorobenzaldehyde (1 mmol) were
inquired (Table 1). To obtain the optimal reaction solvent,
different solvents such as H2O, CH2Cl2, CH3CN, DMF,
toluene, and EtOH in the presence of a certain amount of
catalyst were applied. Among these solvents, EtOH pro-
duced the highest yield of product (Table 1, entry 6), but
the most favorable conditions in terms of rate and yield
when obtained that no solvent was used for the reaction
Fig. 3 VSM magnetization curves of the bare Fe3O4, Fe3O4@SiO2,
and Fe3O4@ SiO2-SO3H nanoparticles
nanoparticles. According to Fig. 5, Fe3O4@ SiO2-SO3H
has a spherical shape with nano dimension ranging from
100 to 140 nm in size.
Screening of reaction conditions
Initially, we investigated the one-pot condensation of
4-hydroxyquinolin-2(1H)-one (1), Meldrum’s acid (2), and
123

E. Abbaspour-Gilandeh et al.
Fig. 5 SEM images of Fe3O4, Fe3O4@SiO2, and Fe3O4@ SiO2-SO3H
Table 1 Effect of the solvent, temperature, reaction time, and amount of the catalyst in the synthesis of pyrano[3,2-c]quinoline-2,5-dione
Entry
Solvent
Cat/mol%
Temp/°C
Time/min
Yield/%
1
CH2Cl2
10
10
10
10
10
10
–
70
80
80
80
80
80
80
80
80
20
20
20
60
80
20
51
58
57
61
68
72
Trace
83
92
86
53
22
86
2
CH3CN
3
Toluene
70
4
DMF
110
100
80
5
H2O
6
EtOH
7
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
70
8
10
10
10
5
60
9
70
10
11
12
13
a
90
70
10
15
25
70
4-Hydroxyquinolin-2(1H)-one (1 mmol), Meldrum’s acid (1 mmol), and 4-chlorobenzaldehyde (1 mmol)
(Table 1, entry 9). To explore the optimal amount of cat-
alyst, the reactions were carried out at different amount of
Fe3O4@SiO2-SO3H ranging from 5 to 15 mol%. It was
found that when the concentration of the catalyst was
10 mol%, we obtained an excellent yield of product in a
short time. Increasing the amount of catalyst beyond this
123

One-pot synthesis of pyrano[3,2-c]quinoline-2,5-dione derivatives by Fe3O4@SiO2-SO3H as an…
led to no substantial improvement in the yield (Table 1,
entry 13), whereas the lower amount of catalyst leads to
reducing the efficiency of the reaction (Table 1, entry 11).
In the absence of the catalyst, the yields of the product fell
sharply and negligible stain was observed on TLC
(Table 1, entry 7). To evaluate the optimum condition, we
also performed several experiments at variable tempera-
tures. At room temperature, the reaction rate is extremely
and the yield is considered low (Table 1, entry 12). The
yield of the product increased up to 70 °C (Table 1, entries
8 and 9). After 70 °C, increasing the reaction temperature
did not show any sign of the enhancement (Table 1, entry
10).
of Meldrum’s acid (2) and aldehyde 3 via the nucleophilic
addition of Meldrum’s acid on the aldehyde activated by
the hydrogen groups of sulfonic acid. The resulting adduct
5 undergoes dehydration to give the intermediate 6. Double
bond in the formed intermediate is highly active due to the
presence of presented oxygen groups in the structure of
Meldrum’s acid and converts it to a strong electrophile. In
the next step, 4-hydroxyquinoline 1 attack to the elec-
trophilic intermediate via the Michael-type addition and
converts to the transition state 7 that via tautomerization
process produced intermediate 8. The resultant intermedi-
ate due to instability produces the final product 4 during a
cyclic process which is accompanied by the release of a
molecule of acetone and carbon dioxide (Scheme 2).
In order to evaluate the performance of the recycled
solid acid catalyst, it was reused after five periods of
recovery for the preparation of the compound (Table 2,
entry 4g). Negligible change in the reaction efficiency is
indicative of recycling solid acid catalyst performance and
expressing the cost-effectiveness of this method (Fig. 6).
Furthermore, a comparative evaluation of the catalytic
efficacy of Fe3O4@SiO2-SO3H was compared with some
of the obtained results in this study with those method-
ologies which have been reported using other earlier
homogeneous catalysts for the synthesis of pyrano[3,2-
c]quinoline-2,5-dione (Table 3). The present methodology
has several merits such as: solvent-free condition, high
reaction rates, effective recovery, use of an inexpensive
catalyst, and less time consuming for the synthesis of
pyrano[3,2-c]quinoline-2,5-dione 4b.
The condensation of 4-hydroxyquinolin-2(1H)-one,
Meldrum’s acid, and aryl aldehydes (carrying both elec-
tron-donating and electron-withdrawing groups), in the
presence of Fe3O4@SiO2-SO3H 10 mol% as a solid acid
catalyst under solvent-free conditions using conventional
heating at 70 °C, prepared desired pyrano[3,2-c]quinoline-
2,5-diones in high purity with good to high yields. The
reactions required 20–38 min with conventional heating at
70 °C (Table 2, compounds 4a–i). The nature of the
functional group on the aryl ring of the aldehyde demon-
strated a slightly different on the reaction time and the
yield of pyrano[3,2-c]quinoline-2,5-dione. More precise
analysis shows that aryl aldehydes with electron donating
substituents (Table 2, compounds 4b–d) react slower than
aryl aldehydes with electron-withdrawing and halogen
substituents (Table 2, compounds 4e–i). These results
clearly indicate that the reactions can tolerate a wide range
of differently substituted aldehydes.
A reasonable pathway of the reaction of 4-hydroxy-
quinolin-2(1H)-one, Meldrum’s acid, and benzaldehyde
conducted in the presence of Fe3O4@SiO2-SO3H is pre-
sented in Scheme 2. The pyrano[3,2-c]quinoline-2,5-dione
synthesis probably begins with Knoevenagel condensation
Conclusion
In summary, a simple, efficient, and green procedure for
the one-pot preparation of pyrano[3,2-c]quinoline-2,5-
dione derivatives in the presence of eco-friendly and reu-
sable solid acid catalyst (Fe3O4@SiO2-SO3H) was
described. The use of green catalyst, lower loading of
catalyst, lack of organic solvent, easy work-up, and good-
to-excellent yields are the advantages of the procedure.
Table 2 Fe3O4@SiO2-SO3H catalyzed synthesis of pyrano[3,2-
c]quinoline-2,5-dione derivatives (Scheme 1)
Product
R
Time/
min
Yield/
a
%
M.p./
°C
References
4a
4b
4c
4d
4e
4f
4g
4h
4i
H
32
35
91
89
85
87
91
90
92
94
87
[300
[300
[300
[300
[300
[300
[300
[300
[300
[29]
[29]
[29]
[30]
[30]
[29]
[29]
[29]
[29]
Experimental
4-CH3
4-OCH3 38
All the pure chemicals were purchased from Merck and
Fluka Chemical Companies and used in the reaction. The
separation and purification of the products were performed
with extraction and recrystallization techniques. Melting
points were measured with an electrothermal-9100 appa-
4-OH
4-NO2
4-F
30
25
27
20
22
28
4-Cl
2,4-Cl2
3-Br
1
ratus. H and 13C NMR spectra were recorded on Bruker
DRX-400 Avance spectrometer at 400.22 and
100.63 MHz, respectively. Mass spectra were determined
a
Yield refers to isolated product
123

E. Abbaspour-Gilandeh et al.
Scheme 2
H
O
O
O3SO
H
O
O
O
O
OH
H
O
O
R
O
H
R
O
H
2
3
5
O
N
R
O
R
4
O
COOH
R
O3SO
H
O
O
O
CO2
H
O
O
O
O
N
R
H
R
9
SiO2
F3O4
6
O
N
R
1
=
Acetone
O
O
O
O
O
O
O
O
O H O3SO
O
H
R
O
R
O
N
N
R
7
8
R
on a Shimadzu QP1100EX mass spectrometer operating at
an ionization potential of 70 eV. Thermogravimetric
analyses (TGA) were conducted using a TGA thermoana-
lyzer (PerkinElmer) instrument. Samples were heated from
25 to 800 °C at ramp 10 °C min-1 under N2 atmosphere.
FT-IR spectra were recorded on a Bruker Alfa FTIR
spectrometer. XRD was performed on a Philips X-Pert
diffractometer using CO tube. SEM was achieved on a
PHILIPS XL30 electron microscope. The magnetic prop-
erties of catalyst were accomplished using vibrating sample
magnetometer/Alternating Gradient Force Magnetometer
(VSM/AGFM, MDK Co, Ltd, Iran).
Fig. 6 Recycling of Fe3O4@SiO2-SO3H as a catalyst under solvent-
free conditions
123

One-pot synthesis of pyrano[3,2-c]quinoline-2,5-dione derivatives by Fe3O4@SiO2-SO3H as an…
Table 3 Comparison of the present method with other reported strategies for the synthesis of compound 4b
Entry
Conditions
Catalyst loading
Time/min
Yield/%
References
1
2
3
4
[Bmim]HSO4/rt
0.5 cm3
50 mol%
1 cm3
80
150
60
85
78
87
89
[29]
L-Proline/EtOH/80 °C
[Hmim]HSO4/ultrasonic
Fe3O4@SiO2-SO3H/70 °C
[29]
[30]
10 mol%
35
This work
General procedure for the synthesis of Fe3O4 nanoparti-
cles (Fe3O4)
General procedure for the preparation of 4-chlorophenyl-
3,4-dihydro-6H-pyrano[3,2-c]quinoline-2,5-diones (4g)
To the mixture of 0.161 g 4-hydroxyquinoline (1 mmol),
0.144 g Meldrum’s acid (1 mmol), and 0.119 g
4-chlorobenzaldehyde (1 mmol) in a vial containing a
magnetic stirring bar was added Fe3O4@SiO2-SO3H
(10 mg) as a catalyst and stirred at 70 °C under solvent-
free conditions. After the completion of the reaction, the
mixture was washed with water (2 9 15 cm3) and then
recrystallized from EtOAc/n-hexane (1:3) to afford the
pure product (92 %).
Fe3O4 MNPs were synthesized using simple chemical co-
precipitation described in the literature [36]. Typically,
2.7 g of FeCl3Á6H2O and 1 g of FeCl2Á4H2O were
dissolved in 100 cm3 of 1.2 mmol aqueous HCl (1:1) by
ultrasonic bath for 30 min. Thereafter, under rapid
mechanical stirring, 150 cm3 of NaOH (1.25 mol dm-3
)
was added under vigorous stirring and a black precipitate
was immediately formed. The resulting transparent solu-
tion was heated at the 80 °C with rapid mechanical stirring
and ultrasound treatment under continuous N2 atmosphere
bubbling. After vigorous stirring for 2 h, the resulting black
MNPs were magnetically separated and washed three times
with deionized water and then, the dried under vacuum at
60 °C for 12 h.
Acknowledgments We gratefully acknowledge financial support
from the Research Council of Islamic Azad University.
References
General procedure for the synthesis of silica functionalized
Fe3O4 nanoparticles (Fe3O4@SiO2)
1. Al-Assar F, Zelenin KN, Lesiovskaya EE, Bezhan IP, Chakchir
BA (2002) Pharm Chem J 36:598
The synthesized Fe3O4 nanoparticles (1 g) were initially
diluted with 20 cm3 water, 60 cm3 ethanol, and 2 cm3
concentrated aqueous ammonia (25 wt%). The suspension
was homogenized under ultrasonification for 25 min. Then,
under continuous mechanical stirring, a solution of 0.5 cm3
TEOS in 10 cm3 ethanol was slowly added to this
dispersion for 16 h. In the final step, the coated particles
were finally separated from the liquid by a magnetic
decantation and washed three times with ethanol. Then, the
dried under vacuum at 70 °C for 5 h [37].
2. Jain RP, Vederas JC (2004) Bioorg Med Chem Lett 14:3655
3. Patil VS, Padalkar VS, Chaudhari AS, Sekar N (2012) Catal Sci
Technol 2:1681
4. Kumar S, Ila H, Junjappa H (2009) J Org Chem 74:7046
5. Wen LR, Shi YJ, Liu GY, Li M (2012) J Org Chem 77:4252
6. Li M, Hou YL, Wen LR, Gong FM (2010) J Org Chem 75:8522
7. Alizadeh A, Rostamnia S, Zhu LG (2010) Tetrahedron Lett
51:4750
8. Rostamnia S, Hassankhani A (2013) RSC Adv 3:18626
9. Ukrainets IV, Bereznyakova NL, Mospanova EV (2007) Chem
Heterocycl Compd 43:856
10. Liang J, Wang S, Wang X, Xu T, Pu X, Shang R, Guo W, Guo Z,
Liu Y, Guo Y, Hua L (2009) 4(3H)-quinolone for preventing
H1N1 type influenza virus. Chinese patent CN 101554380, Oct
14, 2009; (2009) Chem Abstr 151:440623
General procedure for the synthesis of sulfuric acid func-
tionalized Fe3O4 nanoparticles (Fe3O4@SiO2-SO3H)
Fe3O4@SiO2-SO3H microspheres were prepared as fol-
lows; initially, a 500 cm3 suction flask was charged with
1 g Fe3O4@SiO2 MNPs and dispersed in 10 cm3 dry
CH2Cl2 by ultrasonic bath for 30 min. Subsequently, 1 cm3
chlorosulfonic acid (in dry CH2Cl2) was added drop-wise
to a cooled (ice-bath) solution over a 30 min at room
temperature. After the addition was completed, the mixture
was stirred for a further 6-h period until HCl gas evolved
from the reaction vessel. The resulted brown solid MNPs
were collected using an external magnet and washed with
ethanol and water before being dried in an oven at 70 °C.
11. Arya K, Agarwal M (2007) Bioorg Med Chem Lett 17:86
12. Neville CF, Grundon MF, Ramachandran VN, Reisch G, Reisch J
(1991) J Chem Soc Perkin Trans 1:2261
13. Reil E, Hofle G, Draber W, Oettmeier W (2001) Biochim Bio-
phys Acta 1506:127
14. Leeson PD, Williams BJ, Rowley M, Moore KW, Baker R, Kemp
JA (1991) Bioorg Med Chem Lett 3:71
15. Ito C, Itoigawa M, Furukawa A, Hirano T, Murata T, Kaneda N,
Hisada Y, Okuda K, Furukawa H (2007) J Nat Prod 67:1800
16. Koizumi F, Fukumitsu N, Zhao J, Chanklan R, Miyakawa T,
Kawahara S, Iwamoto S, Suzuki M, Kakita S, Rahayu ES, Hos-
okawa S, Tatsuta K, Ichimura M (2007) J Antibiot 60:455
17. Chen JJ, Liao PH, Huang CH, Chen SY (2007) J Nat Prod
70:1444
123

E. Abbaspour-Gilandeh et al.
18. Hostettmann K, Petti MJ, Kubo I, Nakanishi K (1997) Helv Chem
Acta 60:670
29. Rad-Moghadam K, Azimi SC, Abbaspour-Gilandeh E (2013)
Tetrahedron Lett 54:4633
19. Taniguchi M, Haraguchi H, Higuchi F, Oi S, Chapya A, Kubo I
(1985) Agric Biol Chem 49:3051
30. Abbaspour-Gilandeh E, Azimi SC (2015) Iran Chem Commun
3:218
20. Xuesen F, Dong F, Yingying Q, Xinying Z, Jianji W, Philippe
ML, Graciela A, Robert S, Erik DC (2010) Bioorg Med Chem
Lett 20:809
21. Kishore N, Mishra BB, Tripathi V, Tiwari VK (2009) Fitoterapia
80:149
22. Matteelli A, Carvalho AC, Dooley KE, Kritski A (2010) Future
Microbiol 5:849
23. Schiemann K, Finsinger D, Zenke F, Amendt C, Knochel T,
Bruge D, Buchstaller H, Emde U, Stahle W, Anzali S (2010)
Bioorg Med Chem Lett 20:1491
31. Abbaspour-Gilandeh E, Azimi SC, Mohammadi-Barkchai A
(2014) RSC Adv 4:54854
32. Yu JJ, Wang LM, Liu JQ, Guo FL, Liu Y, Jiao N (2010) Green
Chem 12:216
33. Safari J, Zarnegar Z, Heydarian M (2012) Bull Chem Soc Jpn
85:1332
34. Chen Z, Xue Z, Chen L, Geng Z, Yang R, Chen L, Wang Z
(2013) New J Chem 37:3731
35. Sun Y, Duan L, Guo Z, Duan-Mu Y, Ma M, Xu L, Zhang Y, Gu
N (2005) J Magn Mater 285:65
24. Zheng X, Luo S, Zhang L, Cheng JP (2009) Green Chem 11:455
25. Nemati F, Saeedirad R (2013) Chin Chem Lett 24:370
26. Nemati F, Heravi MM, Saeedirad R (2012) Chin J Catal 33:1825
27. Lin Y, Chen H, Lin K, Chen B, Chiou C (2011) J Environ Sci
23:44
36. Hu Y, Zhang Z, Zhang H, Luo L, Yao S (2012) J Solid State
Electrochem 16:857
37. Deng HY, Wang CC, Hu JH, Yang WL, Fu SK (2005) Colloids
Surf A 262:87
28. Mahmoodi NM, Khorramfar S, Najafi F (2011) Desalination
279:61
123