Facile synthesis of TiO2-zeolite composite and its enhanced photocatalytic activity

Article abstract of DOI:10.1007/s10562-013-1119-y

TiO₂-zeolite composite was prepared through synthesis of X-type zeolite in the presence of anatase type TiO₂. The composite had higher acetaldehyde photocatalytic activity than the mixture of the two. In the composite, TiO₂ particle was closely attached to zeolite crystal, and the attachment might support the transfer of acetaldehyde molecules from zeolite to TiO₂. Graphical Abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-013-1119-y

Catal Lett (2013) 143:1255–1259
DOI 10.1007/s10562-013-1119-y
Facile Synthesis of TiO –Zeolite Composite and Its Enhanced
2
Photocatalytic Activity
Satoru Fukugaichi
Naoto Matsue
•
Teruo Henmi
•
Received: 3 September 2013 / Accepted: 22 September 2013 / Published online: 12 October 2013
Ó Springer Science+Business Media New York 2013
Abstract TiO –zeolite composite was prepared through
2
complex and high cost because the precursors of TiO are
2
synthesis of X-type zeolite in the presence of anatase type
expensive. From the above background, Yamaguchi et al.
TiO . The composite had higher acetaldehyde photocata-
2
[18] proposed that simple physical mixture of TiO and
2
lytic activity than the mixture of the two. In the composite,
zeolite can solve the above problems, and showed that
photocatalytic decomposition of 2-propanol increased by
TiO particle was closely attached to zeolite crystal, and
2
the attachment might support the transfer of acetaldehyde
molecules from zeolite to TiO2.
the mixing. In this study, we obtained TiO –zeolite com-
2
posite material through the synthesis of zeolite in the pre-
sence of TiO , and evaluated photocatalytic activity of the
2
Keywords Titanium oxide ꢀ Zeolite ꢀ Composite
material ꢀ Photocatalysis
composite material.
2
Experimental
1
Introduction
2.1 Synthesis Methods
TiO has been extensively investigated as photocatalyst in
2
the oxidative removal of various pollutants [1–7], and
A TiO –zeolite composite material (T/Z) was synthesized
2
composition of photocatalytic TiO with materials with
2
by the following method. A 3.0 g of sodium aluminate
(WAKO, Japan, 1st grade), 10.86 g of sodium hydroxide
(WAKO, Japan, analytical grade), 153 g of distilled water,
2.0 g of TiO2 (TO; FURUKAWA Co. Ltd, FA-55W,
adsorption ability such as activated carbon [8], alumina [9]
and zeolite [10–20] have been studied. Most of these
studies employed preparation methods in which TiO was
2
loaded on the adsorbents, and titanium alkoxide and TiCl4
Japan, 98 %), and 19.28 g of a water glass (SiO : 28 wt%,
2
were used as precursors of TiO . It is difficult to obtain
2
Na O: 9 wt%; MITSUWA Chemical Co. Ltd, Japan), were
2
crystalline TiO2 from the above methods [13] and the
put into a 300 mL flask with a reflux condenser in this
order, then the mixture was stirred for 30 min at room
temperature. The mixture was aged at room temperature
for 24 h, and was boiled on a hot plate for 4 h. Then the
mixture was washed thrice with 30 mL of distilled water,
and heated in an oven at 378 K for 12 h. As described later,
resultant T/Z was composed of X-type zeolite and TiO2,
fabrication process of TiO -loaded zeolite become
2
S. Fukugaichi (&)
Ehime Institute of Industrial Technology, 487-2 Kumekubota,
Matsuyama 791-1101, Japan
e-mail: satoru.fukugaichi@gmail.com
and the content of TiO was 22.6 mass%. Alkali-treated
2
T. Henmi ꢀ N. Matsue
TiO (ATO) was prepared from TO in the same way as T/Z
2
Faculty of Agriculture, Ehime University, 3-5-7 Tarumi,
Matsuyama 790-8566, Japan
e-mail: henmi@agr.ehime-u.ac.jp
except for the addition of sodium aluminate and water
glass. An X-type zeolite with sodium form (ZE) was syn-
thesized by the same way as T/Z except for the addition of
N. Matsue
e-mail: matsue@agr.ehime-u.ac.jp
TO. A physical mixture of zeolite and TiO (T ? Z) was
2
123

1
256
S. Fukugaichi et al.
prepared by mixing mechanically ATO and ZE in the mass
To evaluate the photocatalytic activity of the samples,
the first order reaction rate constant was obtained by the
first order equation using data of the concentration of
acetaldehyde (Eq. 1) and CO2 (Eq. 2) during UV
irradiation.
ratio of 0.226:0.774, in accordance with the TiO content
2
of T/Z.
2
.2 Characterization of Samples
ꢁ
ꢁ
dQ/dt ¼ kacet
Q
ð1Þ
ð2Þ
Elemental analysis was conducted by using a wavelength-
dispersive X-ray fluorescence (WDXRF) spectrometer
dQ/dt ¼ kCO ðQ
ꢁ QÞ
2
max
(
(
PANalytical, PW2400). X-ray powder diffractometry
XRD; Rigaku, RINT2000) was carried out at ambient
where Q is a concentration of acetaldehyde or CO and k is
2
a first order reaction rate constant. Qmax is the amount of
temperature at 2h range of 3°–60° at a scan speed of
CO expected for the complete degradation of acetalde-
2
-
1
˚
0
.05° s using Cu-Ka (k = 1.54056 A). Morphology of
samples was observed with a scanning electron microscope
SEM; JEOL, JSM-6335F). The samples were coated with
hyde injected into the chamber. In this experiment, the
Qmax was 640 ppm.
(
platinum prior to observation. Secondly electron images of
the samples were obtained. Specific surface area from
nitrogen adsorption isotherms at 77 K was measured using
volumetric adsorption equipment (QUANTA CHROME,
Autosorb1). About 30 mg of sample was put into a u6 mm
glass cell. Prior to the measurement, the sample was heated
at 350 °C for 1 h in order to remove water in the sample. The
BET surface area was calculated by seven point BET method
from 0.05 to 0.3 of relative pressure in nitrogen adsorption
data using the Brunauer–Emmett–Teller equation.
3
Results and Discussion
3.1 Characterization of Samples
Figure 1 shows XRD patterns of TO, ATO, ZE, T ? Z,
and T/Z. The untreated TiO (TO) was identified as anatase
2
type from its diffraction peaks at 3.51, 2.38, 1.89, 1.70 and
˚
1
.66 A. No change in the diffraction peak positions was
observed in the XRD pattern of ATO which was boiled
with sodium hydroxide. The XRD peaks of TiO in T/Z
2
2
.3 Photocatalytic Activity Measurement
also showed no change in their position. These observa-
tions confirmed that the boiling treatment with sodium
2
A 100 mg of the sample was put on a glass plate (18 cm ),
and about 1 mL of distilled water was dropped on it. The
suspension was evenly spread out on the glass plate. The
glass plate was air-dried, and heated in an oven at 423 K
for 30 min, and cooled to room temperature in a desiccator.
The glass plate was then exposed to UV irradiation with
UV lamp (AS ONE Corporation, LUV-4, UV intensity:
hydroxide did not change the type of TiO . In addition,
2
SEM images of TiO crystals in ATO (Fig. 2b) and in T/Z
2
(Fig. 2e) were almost the same with those of untreated
TiO (TO; Fig. 2a). The BET surface area of ATO was
2
slightly higher than that of TO (Table 1), and XRD peak
heights of ATO were a little bit lower than those of TO.
These indicated partial dissolution of TiO crystals during
2
-
2
7
5 lW cm ) for 48 h to decompose organic substances.
the boiling treatment with sodium hydroxide. In the XRD
Then the glass plate was placed on the bottom of a chamber
with volume of 314 mL. The chamber was covered with a
lid made of quartz and was evacuated for 10 min, then
synthetic air (21 % O and 79 % N ) passed through a
2
2
water tank kept at 4 °C was flowed through the chamber.
Standard acetaldehyde gas (1.0 vol%) was introduced into
the chamber by syringe so that the concentration of acet-
aldehyde reached 320 ppm (vol/vol). The concentration of
acetaldehyde and carbon dioxide were analyzed by a gas
chromatography (SHIMADZU, GC-12A) with flame ioni-
zation detector equipped with the methanizer (SHIMA-
DZU, MTN-I). After the concentration of acetaldehyde in
the chamber reached adsorption equilibrium in the dark,
UV with a central wavelength of 365 nm (AS ONE Cor-
poration, LUV-4) was irradiated on the sample from above
the chamber. The UV intensity on the samples was mea-
-
2
sured as 75 lW cm by an UV power meter (CUSTOM,
UVA-365).
Fig. 1 XRD patterns of TO, ATO, ZE, T ? Z and T/Z. X X type
zeolite, A anatase type TiO
2
1
23

Facile Synthesis of TiO
2
–Zeolite Composite
1257
Fig. 2 SEM images of a TO (950,000), b ATO (950,000), c ZE (920,000), d T ? Z (955,000) and e T/Z (960,000)
Table 1 BET surface area and the first order reaction constant
pattern of synthetic zeolite, all of the peaks were identified
as those of X-type zeolite (ZE). Diameter of the crystals
was determined as between 1 and 2 lm from SEM
observation (Fig. 2c), and BET surface area was calculated
2
BET (m g
-1
)
-1
acet (s
-1
)
Samples
k
)
kCO2 (s
To
6.62
8.76
514
478
694
2.09
0.73
0.50
3.40
–
0.25
0.22
0.13
0.46
–
ATO
T ? Z
T/Z
2
-1
as 694 m g
.
The composite material, T/Z, showed XRD pattern
containing peaks of both TiO and X-type zeolite, indi-
2
ZE
cating that X-type zeolite was successfully synthesized in
the presence of TiO . The XRD peak positions of TiO and
2
2
X-type zeolite were same as those of TO and ZE samples,
2 -1
was 478 m g , and this is somewhat lower than the
respectively. The content of TiO in T/Z was determined as
2
2
-1
2
2.6 mass% by WDXRF, ignoring the dissolution of TiO2
during the synthesis of X-type zeolite. The SEM image
Fig. 2e) showed that TiO particles were plunged into the
weighted average of 539 m g calculated by considering
contents and BET surface areas of TO and ZE. The
decrease in BET surface area can be ascribed to the close
(
2
large crystals of zeolite, indicating the formation of com-
attachment between TiO and zeolite particles observed by
2
posite of TiO and zeolite. Calculated BET surface area
2
SEM (Fig. 2e).
123

1
258
S. Fukugaichi et al.
acetaldehyde was greater inTO than in ATO. Figure 4
shows changes in the concentration of CO after the UV
2
irradiation, and this indicated that the generation of CO2
with the decomposition of acetaldehyde was higher inTO
than in ATO. The kacet and kco2 values in Table 1 also
showed that photocatalytic activity in the decomposition of
acetaldehyde was higher in TO than in ATO. These
observations indicated that the photocatalytic activity of
TiO2 reduced by the boiling treatment with sodium
hydroxide.
The composite material (T/Z) showed the highest
adsorption and decomposition abilities of acetaldehyde
within the samples (Figs. 3, 4). After the UV irradiation,
Fig. 3 Changes in acetaldehyde concentration with time. UV was
irradiated at 18 min from the beginning of experiment
calculated reaction rate constant for CO generation, kco2 ,
2
-
was 0.46 s (Table 1), and this value was higher than that
1
-
1
of TO and ATO (0.26 and 0.22 s ). Because we prelim-
inarily confirmed that the synthesized X-type zeolite had
no photocatalytic activity, the only material which can
decompose acetaldehyde into CO and H O is TiO . In this
2
2
2
study, each 100 mg of the sample was used. Although the
amout of TiO in T/Z sample was 22.6 mg, the kco value
2
2
of T/Z was higher than that of 100 mg of TO and ATO.
This indicated the generation of a synergy effect between
TiO and zeolite, in the decomposition of acetaldehyde.
2
2
Fig. 4 Changes in CO concentration with UV irradiation time
The physical mixture (T ? Z) showed a little bit lower
adsorptivity than T/Z (Fig. 3). The adsorption of acetal-
dehyde in the dark is mainly due to X-type zeolite con-
In the XRD pattern of the physical mixture of ATO and
ZE (T ? Z), peaks of both TiO and X-type zeolite were
2
tained in them. On the other hand, kco value of T ? Z was
2
-
0.13 s , and this was quite lower than that of T/Z
1
identified, and shift of the peak positions was not observed.
-
(0.46 s ), and also lower than those of TO and ATO.
1
SEM observation reveled that TiO and zeolite particles
2
were separately existed (Fig. 2d). The attachment of small
Because material composition of T ? Z and T/Z is similar
TiO particles onto the large zeolite particles, which was
2
(TiO
suggested that, in the case of T ? Z, little synergy effect
was generated between TiO and zeolite.
Above results indicated that the formation of composite
material of TiO and zeolite through synthesis of zeolite in
the presence of TiO increased photocatalytic activity of
the TiO . Because boiling treatment with sodium hydrox-
ide did not increase the photocatalytic activity of TiO ,
2
2
= 22.6 %, X-type zeolite = 77.4 %), above result
observed in T/Z, was hardly observed. The BET surface
2
-1
area of T ? Z was 514 m g , a little bit smaller than the
2
2
weighted average (539 m g ), and greater than that of
-1
2 -1
T/Z (478 m g ). The greater BET surface area of T ? Z
2
than that of T/Z can be explained by fewer attachment of
2
TiO onto zeolite in T ? Z. From these results, we con-
2
2
cluded that composite of TiO and X-type zeolite (T/Z)
2
was successfully synthesized, by the coexistence of TiO2
during the synthesis of X-type zeolite.
increase in the activity is ascribed to the synergy effect
mentioned above. The synergy effect occurred in T/Z is
assumed to be adsorption and condensation of acetalde-
hyde gas onto the surface of zeolite, and subsequent
3
.2 Photocatalytic Activity Measurement
transfer of acetaldehyde from zeolite to TiO . Similar
2
The results of adsorption and photocatalytic decomposition
experiments of acetoaldehyde gas are shown in Fig. 3. At
the region before the irradiation of UV light, decrease in
the concentration of acetaldehyde is ascribed to the
adsorption of acetaldehyde onto each samples. When we
compared TO and ATO, the amount of adsorption of
acetaldehyde was greater in ATO. However, after the
irradiation of UV, the decrease in the concentration of
synergy effect is also expected in T ? Z, but the distance
between TiO
transfer of acetaldehyde (Fig. 2d). Therefore, the distance
between zeolite (adsorbent) and TiO (photocatalyst) is the
key point for this kind of synergy effect. Similar synergy
effects were reported in the composites of TiO and
adsorbents [8–20], but this is the first study to show
increase in the photocatalytic activity of TiO in a
and zeolite may be too far to enable the
2
2
2
2
1
23

Facile Synthesis of TiO
2
–Zeolite Composite
1259
composite as compared both to TiO2 itself and to the
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2
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2
5
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2
7
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1
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1
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Composite material of anatase type TiO and X-type zeo-
2
lite was prepared by synthesizing X-type zeolite in the
presence of anatase type TiO . Compared to previous
2
15. Tayade RJ, Kulkarui RG, Jasra RV (2007) Ind Eng Chem Res
46:369
methods where TiO was precipitated on the surface of
2
1
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zeolite, this method is more facile and cost-effective. In the
composite material, small TiO2 particles were closely
attached onto the large zeolite crystals. This close attach-
ment allowed the transfer of acetaldehyde gas from zeolite
1
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2
(
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2
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2
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mixture of TiO and zeolite.
2
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