Ag2O/sodium alginate supramolecular hydrogel as a film photocatalyst for removal of organic dyes in wastewater

Article abstract of DOI:10.1039/c6ra28468j

A simple method was proposed to fabricate a Ag₂O supported alginate supramolecular hydrogel film using solution casting technology. The photocatalytic degradability of the film was investigated with methylene blue and malachite green as model dyes. Under irradiation of either UV or visible light, the photodegradation rates were above 93% for both dyes with relatively short degradation times. The film exhibited great adsorptivity of dyes (～76%), highly efficient charge separation and reusability (～90% of its initial activity after five runs). Furthermore, the potential photocatalytic mechanism was explored for the degradation of MB and MG with the film under visible light irradiation. This work provides a new insight into the fabrication of supramolecular hydrogel films as highly efficient photocatalysts for wastewater treatment in practice.

Full text of DOI:10.1039/c6ra28468j

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Ag O/sodium alginate supramolecular hydrogel as
2
a film photocatalyst for removal of organic dyes in
Cite this: RSC Adv., 2017, 7, 15077
wastewater
a
a
b
a
a
ac
Yuhua Ma, Jiajia Wang, Shimei Xu, Zhendong Zheng, Juan Du, Shun Feng*
a
and Jide Wang*
2
A simple method was proposed to fabricate a Ag O supported alginate supramolecular hydrogel film using
solution casting technology. The photocatalytic degradability of the film was investigated with methylene
blue and malachite green as model dyes. Under irradiation of either UV or visible light, the
photodegradation rates were above 93% for both dyes with relatively short degradation times. The film
exhibited great adsorptivity of dyes (ꢀ76%), highly efficient charge separation and reusability (ꢀ90% of its
initial activity after five runs). Furthermore, the potential photocatalytic mechanism was explored for the
degradation of MB and MG with the film under visible light irradiation. This work provides a new insight
into the fabrication of supramolecular hydrogel films as highly efficient photocatalysts for wastewater
treatment in practice.
Received 20th December 2016
Accepted 28th February 2017
DOI: 10.1039/c6ra28468j
rsc.li/rsc-advances
18
19
deposition and sol–gel method on certain solid substrate.
Among which, sol–gel method attracted much attention
Introduction
The efficient removal of organic dyes from wastewater has been because of its distinct advantages including easier adjustment
attracting a great deal of attention due to its ecological and of composition and fabrication of large-area lms, low cost and
1–4
20
environmental importance. Over the past several decades, simple deposition equipment and so on. However, the pho-
various techniques, e.g. adsorption, precipitation, coagulation tocatalytic activity of the lm would be negatively affected by the
1
4
and membrane separation, have been developed and applied to substrate through decrease the surface area and mobility.
5
–7
the treatment of organic dyes in wastewater. But further
Recently, metal–polymer supramolecular hydrogel (SMH)
handling, high power consumption and operating costs seri- has the unique 3D network structure as conventional hydrogel
ously limit their application in the manufacturing industry. As possessing, but the preparation was much more rapidly and
a comparison, photocatalysis is highly efficient, more economic economically. SMH can be advised spontaneously with
and greener.
Utilizing solar energy, organic dyes can be metallic cations as nodes and polymers through supramolec-
translated directly into environmentally safe products, water, ular complexation. It has been successfully utilized in the
8,9
21
10,11
22
9,12,13
23
carbon dioxide, mineral ions, etc.
fabrication of metal nanoparticles and stimuli-responsive
22
Nowadays, the most of reported photocatalysts are mainly in hydrogel. Based on the steric structure of it, SMH should
particle form. However, due to the inherent nature of the also be acted as a promising candidate for the photo-
particle, it was difficult for post-separation and recycling, easy degradation of dyes theoretically, if the metallic node was
9,14,15
aggregation and corrosion.
Above defects can be solved in substituted with one atom or molecule with photocatalytic
some degree by immobilizing catalysts on lms. Moreover, they activity. But no reports on the feasibility of it as photocatalyst
can provide fast charge carrier transport and can be regenerated system were found.
and reused in a sustainable manner. Till now, a series of lm-
form photocatalysts were proposed through various approach, friendly and cost-effective method was proposed to prepare one
Based on the point of view, one facile, environmentally
16
17
such as sputtering, pulsed laser deposition, spray pyrolysis free-standing alginate SMH lm immobilized with Ag
2
O, one of
the most promising photocatalysts for the degradation of dyes
24,25
but seldom used as the principal photocatalytic material.
a
Key Laboratory of Oil & Gas Fine Chemicals, Ministry of Education, Xinjiang Uyghur The morphology, structure and spectral information of it were
Autonomous Region, College of Chemistry and Chemical Engineering, Xinjiang
University, Urumqi, 830046, China. E-mail: fengshunxd@hotmail.com; awangjd@
yahoo.com.cn
characterized by multi-analytical tools. The photocatalytic
activity of the as-prepared SMH lm was investigated in
aqueous solution with methylene blue (MB) and malachite
green (MG) as model dyes under UV or visible light irradiation,
respectively.
b
College of Chemistry, Sichuan University, Chengdu 610064, China
c
School of Life Science and Engineering, Southwest Jiaotong University, Chengdu
6
10031, China
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where R is the degradation rate, A
0
is the absorbance of the
Experimental
Preparation of supramolecular hydrogel lm
original solution, and A is the absorbance of the solution at any
t
time.
All chemicals were analytical grade and used without further
purication. Solutions were prepared in de-ionized water. The
Results and discussion
Formation of supramolecular hydrogel lm
formation procedure of Ag O/ALG SMH lm was followed: in
2
3
brief, a cuboid glass plate (8.3 ꢁ 8.4 ꢁ 0.1 cm ) was casted by 7
mL of 2% (w/v) ALG solution. And then it was placed immedi-
ately into a glass culture dish containing 100 mL of 3% (w/v)
ALG is one kind of biopolymers, and owns both carboxylic and
hydroxylic binding sites. Gelling and metal binding properties
of it have been in the focus of research for many years. ALG can
AgNO solution. Two seconds later, the SMH lm was formed
3
2
+
2+
2+
3
and further kept in AgNO solution for 30 min. Aer that, the
react with various metal cations (Ca , Sr or Ba ) and form
plate was taken out, and the lm was removed out carefully. The
resulted lm was thoroughly rinsed with de-ionized water to
26
SMH with the characteristic egg-box structure. In this work, it
+
was used to fabricate SMH with Ag . The hydrogelation proce-
+
+
remove any excess Ag on the surface of the lm. Finally, it was
dure was straight-forward, requiring simply substituent of Na
+
+
irradiated with a 250 W high pressure mercury lamp for 60 min.
The lm was stored in pure water before use.
of ALG with Ag , and Ag would undergo the complexation with
the ALG chains to form interwoven networks. It took only two
seconds to nish the hydrogelation. Finally, the lm was irra-
+
diated in water to translate Ag into Ag
2
O in situ.
Characterization
The dynamic rheological measurement was performed with
a stress-controlled rheometer (Discovery HR-1, TA) using a 400
2
Characterization of Ag O/ALG SMH lm
mm cone plate. Phase identication study of the hydrogel was The mechanical properties of Ag
carried out by XRD spectrum (XRD) using X-ray diffractometer acterized by rheology at 25 C. Firstly, the dynamic strain sweep
2
O/ALG SMH lm were char-
ꢂ
ꢂ
ꢂ
(
D8 Advance, Bruker) in 2q range of 10–80 at a scan rate of 6
was conducted within the strain region of 0.01–100% with
a frequency of 1.0 rad s , and the corresponding strain was
ꢃ1
ꢃ1
˚
min with Cu Ka radiation (l ¼ 1.54178 A). The lm's surface
conditions and valence states in each component were charac- determined to be 0.5%. Then a dynamic frequency sweep
ꢃ1
terized by an X-ray photoelectron spectroscopy (XPS, ESCALAB experiment was carried out in the region of 0.1–100 rad s at
0
2
50 Xi, Thermo Scientic) using monochromatized Al Ka exci- the strain of 0.5%. As shown in Fig. 1, the storage modulus G
0
0
tation. All the binding energies were calibrated by referencing values of the lm were greater than the loss modulus G values
the C 1s peak at 284.6 eV. The morphology of the lm was over the whole measurement period. It indicated that the
investigated using a eld-emission scanning electron micros- hydrogel possessed a permanent network and was a supramo-
27–30
copy (FESEM, S-4800, Hitachi) and a transmission electron lecular hydrogel.
microscopy (TEM, JEM-2010F, JEOL). Surface area and pore size
Fig. 2 was the XRD spectrum of the lm. In which, the
ꢂ
ꢂ
ꢂ
ꢂ
distribution of the lm were measured by a JW-BK static diffraction peaks at 27.82 , 32.28 , 38.03 and 46.29 were
nitrogen adsorption instrument (Beijing JWGB Sci. & Tech. Co., respectively assigned to the (1 1 0), (1 1 1), (2 0 0) and (2 1 1)
Ltd.). The static contact angle of oil on the lm was measured at diffraction planes of Ag
ambient temperature using
contact angle goniometer testied a certain amount of Ag
JC2000C, Powereach Co.). UV-vis diffuse reectance spectra linity. XPS survey spectrum (Fig. 3a) revealed that the main
UV-vis DRS) were measured in the range of 200–1100 nm on elements of the lm were C, Ag and O. The content of Ag O in
O (JCPDS no. 41-1104). The result
2
a
2
O with high degree of crystal-
(
(
2
a UV-vis diffuse reectance spectrophotometer (4802S, Unico) the lm was as high as 6.72%. In Fig. 3b, the Ag 3d3/2 and Ag
equipped with an integral sphere using BaSO
as a reference. 3d5/2 photoelectrons at 368.4 and 374.4 eV were highly
4
And photoluminescence spectra (PL) were measured using
a uorescence spectrophotometer (F-4500, Hitachi).
Photocatalytic experiments
Firstly, freshly prepared Ag
00 mL of MB or MG solution. And then, it was irradiated by
a high pressure mercury lamp (365 nm, 250 W) or Xe lamp
>390 nm, 500 W) with an optical path of 20 cm. The concen-
2
O/ALG SMH lm was immersed in
1
(
tration of dye in supernatant was monitored by a UV-vis spec-
trometer (Shimadzu UV-1780) at 665 nm to MB or 617 nm to MG
at certain time intervals. The dye degradation rate (R) was then
calculated based on the equation below:
ðA
0
ꢃ A Þ
t
R ¼
(1)
Fig. 1 Dynamic frequency sweep of the Ag
hydrogel film at 0.5% strain.
2
O/ALG supramolecular
A
0
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2
Fig. 2 XRD pattern of Ag O/ALG supramolecular hydrogel film.
Fig. 4 FESEM image of Ag
surface and (c) cross section; TEM spectra of Ag O/ALG supramo-
2
2
O/ALG supramolecular hydrogel film: (a)
31,32
consistent with values of Ag
2
O.
And in Fig. 3c, the rst
component located at 531.3 eV was attributed to the oxygen of lecular hydrogel film: (b) a typical and (d) an enlarged image.
ꢃ
surface OH bound in the lm, which would change into cOH
free radical during the photocatalytic reaction. It would be
33
benecial to photocatalysis process. And the second compo- 30 nm, and the calculated BET specic surface area of the lm
2
ꢃ1
nent at 532.8 eV was corresponded to the oxygen in water was 24.48 m g . The large mesoporous size distribution and
3
4,35
molecules existed in the 3D network structure of the lm.
From FESEM images, it can be found that the lm had organic dyes on their surface, which will contribute to the
a smooth surface with Ag O dispersed evenly and consistently enhancement of photocatalytic activity of catalysts.
Fig. 4a), and an interconnected porous structure was obtained
The underwater oil wettability of the Ag O/ALG SMH lm
Fig. 4c). Based on TEM images (Fig. 4b and d), the same result was evaluated. Firstly, the lm was immersed in aqueous
high BET surface area were advantageous to adsorb more
2
(
(
2
can be obtained. Also from Fig. 4d, it can be found that the size media, and then one droplet of oil (dichloroethane) was dipped
of Ag
2
O was around 8.8 ꢄ 1.0 nm. Such a small size can lead to in solution. As shown in Fig. 6, the oil droplet almost kept as
ꢂ
large photoactive area and high charge separation a complete spherical with a contact angle to the lm of 150.5
24,25,31
a
ꢂ
(larger than 150 ), conrming the superoleophobicity of the
efficiency.
37
The porous nature of the Ag
2
O/ALG SMH lm was deter- lm. Above result demonstrated that the high possibility of
mined by Brunauer–Emmett–Teller (BET) gas sorptometry using Ag O/ALG SMH lm for the selective degradation of
2
38
measurements. The results were illustrated in Fig. 5. The water-soluble organic dyes in aqueous systems.
isotherms were identied as type IV isotherms with type H3
hysteresis loop, the typical characteristic of mesoporous mate-
rials. The pore-size distributions were in the range of 3 to
Photocatalytic property
36
To evaluate the photocatalytic activity of Ag
2
O/ALG SMH lm,
degrading behaviors of organic dyes MB and MG were
2
Fig. 3 (a) Survey XPS spectra of Ag O/ALG supramolecular hydrogel Fig. 5 Nitrogen adsorption–desorption isotherms and the corre-
film. Deconvolution of XPS peaks of the Ag
hydrogel film: (b) Ag 3d and (c) O 1s.
2
2
O/ALG supramolecular sponding pore size distribution curve (inset) of Ag O/ALG supramo-
lecular hydrogel film.
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equilibrium time; V is the solution volume and S is the surface
area of the lm.
The calculated adsorption capacity of the lm was 12.62 and
ꢃ2
1
2.25 mg cm to MB and MG, respectively. The high adsorption
capacity to two dyes was attributed to the negatively charged
ALG and the special 3D network structure (the large meso-
porous size distribution and high BET surface area). It was
a comprehensive result of various factors of electrostatic inter-
44
action and space.
Furthermore, the pseudo-rst-order and the pseudo-second-
order modes were employed to describe the above degradation
data as following:
2
Fig. 6 Wetting behavior of Ag O/ALG supramolecular hydrogel film.
ln(q
e
ꢃ q
t
) ¼ ln q
e
ꢃ k
t
1
t
(3)
(4)
t
1
¼ k
þ
investigated. As shown in Fig. 7a, the degradation rate of MB
was increased with the time gone and reached maximum of
2
q
t
2
q
e
q
e
where q
e
and q
t
represented the amount of dye degraded (mg
and k
2
95% in 150 min under visible irradiation or 93% in 180 min
ꢃ2
cm ) at equilibrium and time t, respectively, and the k
values were the kinetic rate constants. As shown in Table 1, the
kinetic data can be accurately described by the pseudo-second-
1
under UV irradiation. The rates were much higher than 76%
obtained in dark for 180 min. To MG, the similar results were
obtained, except that it took 270 min to reach the degradation
equilibrium under either visible or UV irradiation (Fig. 7b).
2
order model with a high correlation coefficient (R > 0.9896).
Compared with Ag-doped TiO
UV light for 300 min) and TiO
2
lm (35%, under irradiation of
/SnO /CuInS lm (92%, under
irradiation of UV + visible light for 12 h), Ag O/ALG SMH lm Light absorption range
39
2
2
2
40
2
showed the highest degradation rate and the shortest degra-
dation time for the photodegradation of MB either under visible
or UV irradiation. The excellent photodegradation performance
was mainly attributed to the special 3D porous network the
SMH lm having, which made it absorb more solar irradiations
and provided numerous approachable channels for charge
Fig. 8 illustrated UV-vis absorption spectrums of Ag O, ALG lm
2
and Ag O/ALG SMH lm. Ag O clearly exhibited a wide and
2
2
strong light absorption in the whole UV-vis range of 200–
8
2
00 nm. While ALG lm showed two weak absorption peaks in
10 and 304 nm. To Ag O/ALG SMH lm, not only the photo-
2
responding range was extended, but also the light absorption
intensity was strengthened. Moreover, it can be estimated that
41,42
transfer.
Furthermore, it is a free-standing lm, which
meant the active sites on both sides of lm can be utilized.
It is well known that the adsorption capacity of the photo-
catalyst is one of the decisive factors affecting the photocatalytic
activity of the catalyst. The high adsorption capacity of photo-
catalyst will facilitate the direct redox reactions of contaminant
the bandgap energy of Ag O/ALG SMH lm was 1.24 eV nar-
2
rower than that of Ag O (ꢀ1.3 eV) based on the intercept of the
2
tangent to the plot. It demonstrated that the designed photo-
2
catalysts should have a better light response than Ag O since
less energy was required to excite electrons from valence band
to conduction band. Meanwhile light harvesting was improved
43
molecules. From Fig. 7, it can be seen that over 76% MB or MG
was adsorbed by the Ag O/ALG SMH lm. The adsorption
capacity of the lm was calculated from the following equation:
2
through efficient light scattering due to the special 3D structure
12
2
of Ag O/ALG SMH lm. And the extended light absorption
ðC
0
ꢃ C
e
Þ ꢁ V
range meant a broader spectral range of light (e.g. sunlight) can
be utilized by the photocatalyst, therefore enhancing signi-
cantly the performance of photocatalysis.
q
e
¼
(2)
S
45
where q is the adsorption capacity, C is the initial concentra-
e
0
tion of the dye; C is the concentration of dye in solution at
e
2
Table 1 Kinetic parameters of Ag O/ALG supramolecular hydrogel
film on MB and MG degradations at room temperature
Pseudo-rst-order
model
Pseudo-second-order
model
ꢃ2
2
ꢃ2
2
Dyes
MB
Light
q
e
(mg cm
)
R
q
e
(mg cm
)
R
Dark
UV
Visible
Dark
UV
8.789
8.527
6.097
7.957
0.9824
0.9807
0.9779
0.9897
0.9540
0.9816
12.62
15.50
15.11
12.25
15.22
15.70
0.9896
0.9981
0.9998
0.9955
0.9921
0.9982
MG
Fig.
7
Photocatalytic properties of Ag
2
O/ALG supramolecular
12.33
7.270
hydrogel film on (a) MB and (b) MG solutions at room temperature.
Visible
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Fig. 8 UV-vis diffuse reflectance spectra of samples.
Separation of photogenerated electron–hole pairs
Fig. 10 Recycle and reuse of photocatalysts for (a) MB and (b) MG
degradation under visible light irradiation; FESEM image of Ag O/ALG
2
Effective separation of the photogenerated electron–hole pairs supramolecular hydrogel film: (c) fresh and (d) used after five
successive reactions (oblique lines, Ag
hydrogel film; straight line, Ag O).
2
O/ALG supramolecular
is crucial for high-efficiency photocatalysts. In this work, PL was
2
employed to investigate the interfacial charge-transfer process
46
2 2
between Ag O and ALG in Ag O/ALG SMH lm. From Fig. 9, it
can be found that the emission wavelength of the lm was no
distinct alteration aer ALG introduced into lm. However,
As comparison, Ag O almost lost its photodegradation activity
2
15,48,49
in the third to MB and the fourth run to MG.
Here, the

2
uorescence intensity of Ag O/ALG SMH lm decreased, indi-
commercial ALG powders was also added directly into the
solution of MB or MG. It was found that the concentration of
MB or MG in the solution was decreased about 43.5% and
cating that the lm had a higher separation rate of photo-
generated electrons and holes than Ag O having.
2
1

5.5% of its original concentration when ALG powders was used
rst time. When above pure ALG powders was used repeated,
2
Reusability of Ag O/ALG SMH lm
the concentration of dyes in solution was not change to either
MB or MG with/without visible light irradiating. It demon-
strated that the decrease of dye concentrations at pure ALG used
in the rst run was caused by the physical absorption of pure
ALG powders, not the degradation of MB or MG. It indicated
that pure ALG had no photocatalytic activity for the degradation
of MB or MG.
Theoretically, photogenerated holes in Ag O could transfer to
2
2
ꢃ
the ALG (electron donors) before oxidizing the lattice O and
photogenerated electrons would be captured by O before
reducing lattice Ag . Above two processes would be helpful to
maintain the structure of Ag O in Ag O/ALG SMH lm under
2
+
2
2
47
light irradiation. To validate the assumption, it was used to
photodegrade MB and MG successively. As shown in Fig. 10a
and b, the catalytic activity of the Ag O/ALG SMH lm can retain
2
over 90% of its initial activity aer ve cycles. And it hardly to
Potential photocatalytic mechanism

nd difference between FESEM and XRD images of the lm
The photocatalytic mechanism of degradation of MB and MG
was explored. A set of free radical trapping experiments
were performed by introducing scavenger of nitrogen
before and aer ve successive cycles of the reaction (Fig. 10c,
d and 11). Above results testied the high stability the lm had.
Fig. 9 Photoluminescence spectra of Ag
molecular hydrogel film.
2
O and Ag
2
O/ALG supra- Fig. 11 XRD spectra of fresh and used Ag
2
O/ALG supramolecular
hydrogel film.
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showed great adsorptivity of organic dyes, superoleophobicity,
extended photoresponding range, and enhanced charge sepa-
ration and transportation properties. It exhibited excellent
photocatalytic degradability to organic dyes of MB and MG
either under UV or visible light irradiation. Potential mecha-
nism to photodegrade MB and MG was explored. It was found
+
that h and cOH were the main active species contributing to the
excellent photocatalytic degradation of the dyes. The lm also
showed high stability and reusability. We hope this nding
could become a helpful template for people want to fabricate
new type of photocatalyst.
Fig. 12 The effect of different scavengers on the degradation of (a) MB
2
and (b) MG in the presence of Ag O/ALG supramolecular hydrogel film
(
MEL: methanol; IPA: isopropanol).
Acknowledgements
This work was supported by the Doctor Student Research
Innovation Project of Xinjiang (XJUBSCX-2014009), Natural
Science Foundation of China (51541308) and NSFC-Xinjiang
Joint Fund for Local Outstanding Youth (U1403392).
References
1
2
Z. Xiong and X. S. Zhao, J. Am. Chem. Soc., 2012, 134, 5754.
S. Wang, Y. Guan, L. Wang, W. Zhao, H. He, J. Xiao, S. Yang
and C. Sun, Appl. Catal., B, 2015, 25, 448.
Fig. 13 The photocatalytic mechanism for the degradation of MB and
3
4
5
C. Baslak, G. Arslan, M. Kus and Y. Cengeloglu, RSC Adv.,
MG with the Ag
2
O/ALG supramolecular hydrogel film photocatalyst.
2016, 6, 18549.
W. Li, Y. Tian, P. Li, B. Zhang, H. Zhang, W. Geng and
Q. Zhang, RSC Adv., 2015, 5, 48050.
C. Yang, U. Kaipa, Q. Z. Mather, X. Wang, V. Nesterov,
A. F. Venero and M. A. Omary, J. Am. Chem. Soc., 2011, 133,
ꢃ
+
(N
2
, O
2
c
quencher), 10 mL methanol (MEL, h scavenger) or
isopropylalcohol (IPA, cOH radical scavenger) in the photo-
catalytic degradation process. As shown in Fig. 12a, the degra-
dation rate slightly decreased by purging N2 ow into the
18094.
6
7
J. Dou, S. Yin, J. Y. Chong, B. Zhang, J. Han, Y. Huang and
R. Xu, Appl. Catal., A, 2016, 513, 106.
B. P. Nenavathu, A. V. R. Krishna Rao, A. Goyal, A. Kapoor
and R. K. Dutta, Appl. Catal., A, 2013, 459, 106.
ꢃ
solution, indicating that few O2c was involved in the degra-
dation of MB. Notably, the photocatalytic degradation of MB
decreased obviously with the addition of MEL or IPA. Therefore,
+
it could be concluded that h and cOH were the main active
ꢃ
8 J. Han, H. Y. Zeng, S. Xu, C. R. Chen and X. J. Liu, Appl. Catal.,
A, 2016, 527, 72.
9
species rather than O
2
c . The effects of above scavengers on the
photodegradation rate of MG were almost as same to MB
C. Wang, J. Li, X. Lv, Y. Zhang and G. Guo, Energy Environ.
Sci., 2014, 7, 2831.
+
(
Fig. 12b). The results demonstrated that h and cOH were the
major reactive species of Ag O/ALG SMH lm for the photo-
2
10 F. Lin, Y. Zhang, L. Wang, Y. Zhang, D. Wang, M. Yang,
degradation of MB and MG.
Combined with above discussion and experiments, one
possible mechanism for the photodegradation of MB and MG
with Ag O/ALG SMH lm was proposed and shown in Fig. 13.
2
Firstly, the MB and MG were adsorbed by the lm. Secondly,
J. Yang, B. Zhang, Z. Jiang and C. Li, Appl. Catal., B, 2012,
1
27, 363.
1 L. Dong, D. Liang and R. Gong, Eur. J. Inorg. Chem., 2012,
012, 3200.
2 N. Wang, Y. Zhou, C. Chen, L. Cheng and H. Ding, Catal.
Commun., 2016, 73, 74.
3 M. Zhang, W. Jiang, D. Liu, J. Wang, Y. Liu, Y. Zhu and
Y. Zhu, Appl. Catal., B, 2016, 183, 263.
4 D. Zhang, W. Wang, F. Peng, J. Kou, Y. Ni, C. Lu and Z. Xu,
Nanoscale, 2014, 6, 5516.
1
1
1
1
1
1
2
irradiated by the light, electrons were excited from valence band
to conduction band, and were captured by O . At the same time,
2
the abundant holes were le in valence band and transferred to
4
7
+
ALG (electron donors). The le h would generate cOH radi-
+
2 2
cals. Finally h and cOH oxidized the MB and MG into H O, CO
and other inorganic salts.
5 C. Yu, G. Li, S. Kumar, K. Yang and R. Jin, Adv. Mater., 2014,
26, 892.
6 S. Lee, E. Yamasue, H. Okumura and K. Ishihara, Appl. Surf.
Sci., 2015, 324, 339.
Conclusions
In summary, Ag O/ALG SMH lm photocatalyst was prepared by 17 R. Edla, N. Patel, M. Orlandi, N. Bazzanella, V. Bello,
2
a solution casting technology. Aer that, Ag
situ onto the lm by a convenient and “green” method. The lm
2
O were grown in
C. Maurizio, G. Mattei, P. Mazzoldi and A. Miotello, Appl.
Catal., B, 2015, 166–167, 475.
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Paper
RSC Advances
1
1
2
2
2
2
2
2
2
2
2
2
8 N. Hahn, S. Hoang, J. Self and C. Mullins, ACS Nano, 2012, 6, 34 T. Jiao, H. Guo, Q. Zhang, Q. Peng, Y. Tang, X. Yan and B. Li,
712. Sci. Rep., 2015, 5, 11873.
9 Y. Lim, C. Chua, C. Lee and D. Chi, Phys. Chem. Chem. Phys., 35 N. Salami, M. R. Bayati, F. Golestani-Fard and H. R. Zargar,
014, 16, 25928. Mater. Res. Bull., 2012, 47, 1080.
0 Y. Li, L. Xu, X. Li, X. Shen and A. Wang, Appl. Surf. Sci., 2010, 36 Y. Chen, G. Tian, G. Mao, R. Li, Y. Xiao and T. Han, Appl.
56, 4543. Surf. Sci., 2016, 378, 231.
1 S. Bai, C. Sun, H. Yan, X. Sun, H. Zhang, L. Liang, X. Lei, 37 L. Zhang, Y. Zhong, D. Cha and W. Peng, Sci. Rep., 2012, 3,
P. Wan and X. Chen, Small, 2015, 11, 5807. 670.
2 Z. Sun, F. Lv, L. Cao, L. Liu, Y. Zhang and Z. Lu, Angew. 38 T. Wu, Q. Shao, S. Ge, L. Bao and Q. Liu, RSC Adv., 2016, 6,
Chem., Int. Ed., 2015, 54, 7944. 58020.
3 H. Yabu, K. Koike, K. Motoyoshi, T. Higuchi and 39 A. Guill ´e n-Santiago, S. May ´e n, G. Torres-Delgado,
7
2
2
M. Shimomura, Macromol. Rapid Commun., 2010, 31, 1267.
4 W. Zhou, H. Liu, J. Wang, D. Liu, G. Du and J. Cui, ACS Appl.
Mater. Interfaces, 2010, 2, 2385.
R. Castanedo-P ´e rez, A. Maldonado and M. D. L. L. Olvera,
Mater. Sci. Eng., B, 2010, 174, 84.
40 A. Enesca, M. Baneto, D. Perniu, L. Isac, C. Bogatu and
A. Duta, Appl. Catal., B, 2016, 186, 69.
5 G. Wang, X. Ma, B. Huang, H. Cheng, Z. Wang, J. Zhan,
X. Qin, X. Zhang and Y. Dai, J. Mater. Chem., 2012, 22, 21189. 41 J. Cai, W. Liu and Z. Li, Appl. Surf. Sci., 2015, 358, 146.
6 O. Smidsrød and G. Skj ˚a kbraek, Trends Biotechnol., 1990, 8, 42 H. Maleki, Chem. Eng. J., 2016, 300, 98.
7
1.
43 W. Morales, M. Cason, O. Aina, N. R. de Tacconi and
K. Rajeshwar, J. Am. Chem. Soc., 2008, 130, 6318.
44 J. Xu, L. Yang, X. Hu, S. Xu, J. Wang and S. Feng, So Matter,
2015, 11, 1794.
45 Y. Lu, Y. Lin, D. Wang, L. Wang, T. Xie and T. Jiang, Nano
Res., 2011, 4, 1144.
7 Y. Zhou, H. Cui, C. Shu, Y. Ling, R. Wang, H. Li, Y. Chen,
T. Lu and W. Zhong, Chem. Commun., 2015, 51, 15294.
8 X. Li, G. Pu, X. Yu, S. Shi, J. Yu, W. Zhao, Z. Luo, Z. He and
H. Chen, RSC Adv., 2016, 6, 62434.
9 H. Komatsu, S. Matsumoto, S. Tamaru, K. Kaneko, M. Ikeda
and I. Hamachi, J. Am. Chem. Soc., 2009, 131, 5580.
0 S. Zu and B. Han, J. Phys. Chem. C, 2009, 113, 13651.
46 W. Zou, L. Zhang, L. Liu, X. Wang, J. Sun, S. Wu, Y. Deng,
C. Tang, F. Gao and L. Dong, Appl. Catal., B, 2016, 181, 495.
3
3
1 M. Xu, L. Han and S. Dong, ACS Appl. Mater. Interfaces, 2013, 47 X. Wang, S. Li, H. Yu, J. Yu and S. Liu, Chem.–Eur. J., 2011, 17,
, 12533. 7777.
2 H. Yu, R. Liu, X. Wang, P. Wang and J. Yu, Appl. Catal., B, 48 H. Wang, J. Li, P. Huo, Y. Yan and Q. Guan, Appl. Surf. Sci.,
012, 111–112, 326. 2016, 366, 1.
3 T. Sakamoto, T. Iida, T. Sekiguchi, Y. Taguchi, N. Hirayama, 49 S. Yang, D. Xu, B. Chen, B. Luo and W. Shi, Appl. Catal., B,
K. Nishio and Y. Takanashi, J. Phys. D: Appl. Phys., 2008, 41, 2017, 204, 602.
080.
5
3
3
2
3
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