Significant enhancement of visible light photocatalytic activity of the hybrid B12-PIL/rGO in the presence of Ru(bpy)32+ for DDT dehalogenation

Article abstract of DOI:10.1039/c7ra02062g

A new B₁₂-PIL/rGO hybrid was prepared successfully through immobilizing a B₁₂ derivative on the surface of poly(ionic liquid) (PIL)-modified reduced graphene oxide (rGO) by electrostatic attraction and π-π stacking attraction among the different components. The hybrid catalyst showed an enhanced photocatalytic activity in the presence of Ru(bpy)₃²⁺ for 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT) dechlorination with ～100% conversion. Especially, the yield of didechlorinated products could reach 78% after 1 h of visible light irradiation, which should be attributed to a synergistic effect of B₁₂, rGO and PIL in B₁₂-PIL/rGO, including their respective catalytic performance, the excellent electron transport of rGO and the concentration of DDT and 1,1-bis(4-chlorophenyl)-2,2-dichloroethane (DDD) on the surface of B₁₂-PIL/rGO. Furthermore, the hybrid catalyst was easily recycled for use without obvious loss of catalytic activity.

Full text of DOI:10.1039/c7ra02062g

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Significant enhancement of visible light
photocatalytic activity of the hybrid B12-PIL/rGO in
Cite this: RSC Adv., 2017, 7, 19197
the presence of Ru(bpy)32+ for DDT dehalogenation
a
a
Ying Sun, Wei Zhang, Jian Tong,a Yu Zhang,a Shuyao Wu,a Daliang Liu,a
*
Hisashi Shimakoshi,b Yoshio Hisaedab and Xi-Ming Song
*
a
A new B12-PIL/rGO hybrid was prepared successfully through immobilizing a B12 derivative on the surface of
poly(ionic liquid) (PIL)-modified reduced graphene oxide (rGO) by electrostatic attraction and p–p stacking
attraction among the different components. The hybrid catalyst showed an enhanced photocatalytic activity
2+
in the presence of Ru(bpy)3 for 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT) dechlorination with
ꢀ100% conversion. Especially, the yield of didechlorinated products could reach 78% after 1 h of visible light
irradiation, which should be attributed to a synergistic effect of B12, rGO and PIL in B12-PIL/rGO, including
their respective catalytic performance, the excellent electron transport of rGO and the concentration of DDT
and 1,1-bis(4-chlorophenyl)-2,2-dichloroethane (DDD) on the surface of B12-PIL/rGO. Furthermore, the
hybrid catalyst was easily recycled for use without obvious loss of catalytic activity.
Received 19th February 2017
Accepted 20th March 2017
DOI: 10.1039/c7ra02062g
rsc.li/rsc-advances
poly(ionic liquid),7,11 which could allow efficient electron transfer
Introduction
from the Ru(bpy)32+ moiety to the cobalt center in the B12 complex.
However, these soluble polymer catalysts are difficult separate
from the catalytic system.
Dehalogenation reactions have attracted great interest for their
potential application in the treatment of halogenated solvent
wastes and also as remedial approaches to remove organo-
chlorine pesticide residues from contaminated soils.1,2 It has
been found that vitamin B12 and its derivatives could be used as
efficient dehalogenation catalysts since they can form Co(I)
species which are supernucleophiles and can react with an alkyl
halide to form Co(III)–alkyl intermediates.3–6 Aiming to establish
more effective, green and reusable catalytic systems for deha-
logenation, some hybrid catalysts fabricated by immobilizing
B12 derivatives on a matrix for photocatalytic dehalogenation
have been reported in recent years.7–12 In 2009, the Hisaeda group9
synthesized a hybrid catalyst, B12–TiO2, through immobilizing
a B12 derivative, cobyrinic acid, on the surface of TiO2. It could
effectively dehalogenate various organic halides, such as DDT,
DDD, and phenethyl bromide, under UV light irradiation (365
nm). In this catalytic system, TiO2 acted as a photosensitizer and
supernucleophilic CoI was formed by electron transfer from TiO2
during light irradiation. In order to fully utilize solar energy, we
subsequently prepared two copolymer catalysts through immobi-
lizing a B12 derivative as catalyst and [Ru(bpy)3]2+ as photosensi-
tizer on the same polymer backbone, namely polystyrene and
Graphene as a novel carbon-based nanomaterial has been
investigated in many elds including catalysis,13,14 drug delivery,15
biosensors,16 photochemical devices17 and energy storage.18 In
recent years, some hybrid catalysts based on graphene have been
shown to exhibit high catalytic activities in photocatalytic reactions
such as photocatalytic decomposition of organic pollutants, pho-
tocatalytic reduction of CO2 and splitting of H2O19–21 due to gra-
phene's excellent conductivity, superior electron mobility, large
surface to volume ratio, high chemical stability and so on.22–26 To
our knowledge, B12 in combination with graphene for dehaloge-
nation reactions has not been reported. Here, a novel B12-based
hybrid catalyst (B12-PIL/rGO) was prepared, as shown in Fig. 1, by
immobilizing a B12 derivative on the surface of poly(ionic liquid)
(PIL)-modied reduced graphene oxide (rGO) through electrostatic
attraction, where the PIL was utilized as a stabilizer to avoid the
aggregation of rGO sheets and also made the surface of rGO sheets
partly positively charged,27,28 and then its photocatalytic activity
was investigated for DDT dechlorination reaction in the presence
of the photosensitizer Ru(bpy)32+ under visible light irradiation.
Experimental section
Materials
aLiaoning Key Laboratory for Green Synthesis and Preparative Chemistry of Advanced
Materials, College of Chemistry, Liaoning University, Shenyang 110036, P. R. China.
E-mail: weizhanghx@lnu.edu.cn; songlab@lnu.edu.cn; Fax: +86-24-62207922; Tel:
+86-24-62207792
Flake graphite (99.95% purity, average diameter of 1 mm) was
purchased from Qingdao Xiyou Graphite Co. Ltd. 1,1-Bis(4-
chlorophenyl)-2,2,2-trichloroethane (DDT) and Ru(bpy)3Cl2
were purchased from J & K Scientic Ltd. Cyanoaqua cobyrinic
bDepartment of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu
University, Motooka, Fukuoka 819-0395, Japan
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Fig. 1 Illustration of the preparation of the B12-PIL/rGO hybrid.
acid [(CN)(H2O)Cob(III)7COOH]Cl was synthesized according to (0.2 M) was degassed aer three freeze–pump–thaw cycles.
the literature.9 Graphene Oxide (GO) was prepared using Then the solution was irradiated for 1 h using a xenon lamp
a modied Hummers' method as described in our previous with a l > 400 nm optical lter and a heat cut-off lter. Aer
work.17 1-Vinyl-3-ethylimidazolium bromide (ViEtIm+Brꢁ) and removing the solvent by evaporation, the residue was washed
poly(ViEtIm+Brꢁ) were synthesized according to the literature.29 with hexane three times and the products and the unreacted
substrate were dissolved in hexane. Aer removing the solvent,
a white solid was obtained and analyzed by 1H NMR using 1,4-
Characterizations
dioxane as the internal standard. The B12-PIL/rGO hybrid cata-
lyst was washed with methanol, and then reused aer adding
fresh triethanolamine, Ru(bpy)3Cl2 and the substrate.
The FT-IR spectra were recorded with a PerkinElmer 1600 FT-IR
spectrophotometer. The UV-visible spectra were obtained with
a PerkinElmer Lambda 25 spectrophotometer. The NMR spectra
were recorded with a Mercury Vx-300 MHz NMR spectrometer. The
SEM images and EDS analysis were acquired using a Hitachi SU-
8010 equipped with an EDX analyzer operated at an accelerating
voltage of 15 kV. The TEM images were obtained with a JEM 2100
Results and discussion
Preparation and characterization of B12-PIL/rGO nanosheets
operating at 200 kV. XRD patterns were obtained with a Bruker D8-
Advance. Raman spectra were obtained using a Renishaw inVia
Raman microscope with excitation laser wavelength at 633 nm.
Fig. 1 illustrates the preparation procedure for B12-PIL/rGO. GO
was reduced to rGO by hydrazine hydrate in poly(ViEtIm+Brꢁ)
aqueous solution and the PIL/rGO composite was fabricated
directly in the suspension because of the electrostatic and p–p
interactions between rGO and poly(ViEtIm+Brꢁ). The B12
derivative [(CN)(H2O)Cob(III)7COOH]Cl was subsequently xed
on the surface of the PIL/rGO nanosheets through electrostatic
self-assembly between imidazolium cations and the B12 deriv-
ative aer it was added to the suspension. High dispersity of
a catalyst can effectively improve its catalytic activity for
a heterogeneous catalytic system, and thus the dispersity of the
hybrid in each of water and methanol was evaluated. Compared
to rGO, this hybrid exhibited improved dispersity in water and
methanol due to the introduction of PIL and the water-soluble
B12 derivative on the surface of rGO. As shown in Fig. 2, the
dispersion of B12-PIL/rGO in methanol possessed high stability,
while almost all the rGO settled out from the dispersion aer
standing for 1 h.
Preparation of PIL/rGO nanosheets
GO (100 mg) was dispersed in aqueous solution (100 mL) con-
taining poly(ViEtIm+Brꢁ) (1 g) by sonication, and then hydrazine
hydrate (0.2 mL) was added. Aer the mixture was stirred at 95 ꢂC
for 12 h, the composite PIL/rGO was obtained by centrifugation.
Then it was washed with distilled water three times to remove the
excess poly(ViEtIm+Brꢁ) and dried in vacuum for 24 h.
Preparation of B12-PIL/rGO
[(CN)(H2O)Cob(III)7COOH]Cl (30 mg) was added to 30 mL
aqueous dispersion of PIL/rGO (50 mg) and the mixture was
stirred at room temperature for 12 h. Then B12-PIL/rGO nano-
sheets were obtained aer centrifugation and washed with
distilled water three times.
The preparation procedure of the hybrid was monitored by
zeta potential measurements. Fig. 3 shows the zeta potential
data of GO (a), PIL/rGO (b) and B12-PIL/rGO (c) in 0.1 M PBS (pH
General catalytic procedure
A 5 mL methanol solution containing B12-PIL/rGO (3 mg), DDT ¼ 7.0). The zeta potential of GO is around ꢁ38.5 mV. Aer GO
(2.4 ꢃ 10ꢁ3 M), Ru(bpy)3Cl2 (5.5 ꢃ 10ꢁ4 M) and triethanolamine was reduced to rGO and further modied by the cationic PIL,
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Fig. 4 FT-IR spectra of GO (a), poly(ViEtIm+Brꢁ) (b), PIL/rGO (c), B12
-
PIL/rGO (d) and B12 catalyst (e).
Fig. 2 Photographs of rGO (a) and B12-PIL/rGO (b) dispersions in
methanol after standing for 1 h at room temperature.
derivative was assembled onto the surface of the PIL/rGO
nanosheets.
the zeta potential of the obtained PIL/rGO signicantly moves to
+42.4 mV. The obvious decrease of the zeta potential of B12-PIL/
rGO at +19.4 mV should be attributed to the introduction of the
B12 derivative. The change of the surface charge in the hybrid
could further indicate that PIL and B12 complex were success-
fully graed onto the rGO surface.
Fig. 5 shows the UV-visible spectra of B12-PIL/rGO, GO, PIL/
rGO and B12 in water. GO exhibits a typical absorption at
228 nm assigned to the p–p* transition of C]C band. In the
spectrum of PIL/rGO, this transition absorption peak is red-
shied to 270 nm, which is attributed to the deoxygenation
and partial restoration of the electronic conjugation aer the
reduction process. Poly(ViEtIm+Brꢁ) does not show an obvious
absorption in the range of 200–800 nm, which coincides with the
literature.29 The B12 derivative exhibits three typical absorption
peaks at 352, 497 and 529 nm.9 Therefore, in the case of B12-PIL/
rGO, the characteristic absorption peaks at 360, 515 and 547 nm
should be assigned to the B12 derivative. The UV-visible spectra
further prove the successful preparation of the B12-PIL/rGO
hybrid.
Dry B12-PIL/rGO, PIL/rGO, rGO and GO powders were each
used in the XRD analysis, as shown in Fig. 6. The XRD analysis
indicates that the interlayer spacing of rGO (2q ¼ 24.5ꢂ, 0.363
nm) decreases obviously compared to that of GO (2q ¼ 11.6ꢂ,
0.762 nm), as a result of the removal of oxygen-containing
groups from the carbon sheets. Compared with rGO, the
diffraction peak of PIL/rGO shied to 2q ¼ 23.2ꢂ, indicating the
slight broadening of interlayer spacing to 0.383 nm due to the
introduction of PIL. Aer the B12 derivative was further
The FT-IR spectra of GO, poly(ViEtIm+Brꢁ), PIL/rGO, the B12
derivative and the resulting B12-PIL/rGO are shown in Fig. 4. The
appearance of characteristic absorption peaks at 1733, 1631 and
1048 cmꢁ1 (stretching vibrations of C]O, C]C and C–O,
respectively) revealed the presence of C]O, C]C and C–O
functional groups in GO. While in the spectrum of PIL/rGO, the
peak at 1733 cmꢁ1 assigned to the C]O stretch of the carboxylic
group of GO completely disappears which proves that GO was
reduced by hydrazine hydrate. The characteristic peaks of imi-
dazolium cations at 1560, 1450 and 1165 cmꢁ1 in the spectrum of
PIL/rGO indicate that poly(ViEtIm+Brꢁ) was assembled onto the
surface of rGO nanosheets successfully. Aer the B12 derivative
was adsorbed on PIL/rGO, the spectrum of the obtained B12-PIL/
rGO presents the typical absorption bands at 1271 cmꢁ1 from the
B12 derivative. These observations also indicate that the B12
Fig. 3 Zeta potential distributions of GO (a), PIL/rGO (b) and B12-PIL/ Fig. 5 UV-visible spectra of B12-PIL/rGO, GO, PIL/rGO and B12 in
rGO (c) in 0.1 M PBS (pH ¼ 7.0).
water.
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shied to 1330 and 1593 cmꢁ1 respectively, proving the exis-
tence of interaction between PIL and rGO. In addition, the ID/IG
ratios of rGO, PIL/rGO and B12-PIL/rGO gradually increase and
are 0.93, 1.01 and 1.05 respectively, reecting the increasing
disorder in the PIL/rGO and B12-PIL/rGO hybrids attributed to
the introduction of PIL and the B12 derivative on the surface of
rGO.
The chemical compositions of PIL/rGO and B12-PIL/rGO
nanosheets were determined by EDS (Fig. 8). Amounts of
62.77% of C, 19.34% of O, 16.27% of N and 1.62% of Br were
found in the PIL/rGO nanosheets, where the N and Br peaks
arose from the imidazole cations and the counter ions of pol-
y(ViEtIm+Brꢁ) respectively, the O peak originated from rGO and
the C peak originated from both rGO and poly(ViEtIm+Brꢁ). In
the spectrum of B12-PIL/rGO, besides C, O, N and Br peaks, an
amount of 0.70% of Co was also detected which should derive
from B12, and the decrease of Br from 1.62% to 0.34% should be
Fig. 6 XRD patterns of B12-PIL/rGO (a), PIL/rGO (b), rGO (c) and GO
(d).
attributed to the part anionic exchange with B12
.
The morphologies of GO and B12-PIL/rGO were characterized
by SEM and TEM. It was found that GO possessed layered
structures with crumpled or wrinkled sheets (Fig. 9A and C).
Compared with GO, B12-PIL/rGO (Fig. 9B and D) displayed
thicker and fewer wrinkled layers, indicating that the structure
of the rGO had not changed aer modication.
The catalytic performance of the hybrid catalyst B12-PIL/rGO
The visible light photocatalytic activity of B12-PIL/rGO was inves-
tigated using DDT as a substrate in the presence of the photo-
sensitizer Ru(bpy)3Cl2 in methanol. The results are summarized in
Table 1. For the B12-PIL/rGO hybrid in the presence of Ru(bpy)3Cl2,
DDT was almost completely converted to dechlorinated products
including 1,1-bis(4-chlorophenyl)-2,2-dichloroethane (DDD, 58%
Fig. 7 Raman spectra of rGO, PIL/rGO and B12-PIL/rGO.
decorated on the PIL/rGO sheets, the diffraction peak of B12
-
PIL/rGO shied to 2q ¼ 22.4ꢂ, corresponding to an interlayer yield), 1-bis(4-chlorophenyl)-2-chloroethane (DDMS, 5% yield),
spacing of 0.397 nm.
1,1,4,4-tetrakis(4-chlorophenyl)-2,3-dichloro-2-butene (TTDB (E/Z),
Raman spectroscopy is usually employed to provide struc- 8% yield) and 1,1-bis(4-chlorophenyl)-2-chloroethylene (DDMU,
tural information for carbon materials. Fig. 7 shows the Raman 10% yield) aer 20 min of visible light irradiation (entry 2 in Table
spectra of rGO, PIL/rGO and B12-PIL/rGO. As shown in Fig. 7, 1). According to the reported formation mechanism of the prod-
rGO shows a disorder-induced D band at 1341 cmꢁ1 and a G ucts of DDT dechlorination, TTDB (E/Z) is the product of coupling
band at 1597 cmꢁ1 resulting from the sp3-hybridized carbon reaction between two didechlorinated carbene intermediates.31
and the sp2-hybridized carbon respectively.29,30 In comparison Therefore, the total yield of didechlorinated products for this
with rGO, the D and G bands of the PIL/rGO hybrid are slightly catalytic system was 31%. When the irradiation time was increased
Fig. 8 EDS spectra of PIL/rGO (left) and B12-PIL/rGO (right).
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Fig. 9 SEM images of GO (A) and B12-PIL/rGO (B); TEM images of GO (C) and B12-PIL/rGO (D).
Table 1 Photocatalytic dechlorination of DDT catalyzed by B12-PIL/rGOa
Product yieldb (%)
Irradiation time
(min)
Conversion
(%)
Entry
Catalyst and photosensitizer
DDD
DDMS
TTDB (E/Z)
DDMU
1
2
B12-PIL/rGO, Ru(bpy)3Cl2
B12-PIL/rGO, Ru(bpy)3Cl2
B12-PIL/rGO, Ru(bpy)3Cl2
B12-PIL/rGO, Ru(bpy)3Cl2
Only Ru(bpy)3Cl2
Only B12-PIL/rGO
B12, Ru(bpy)3Cl2
PIL/rGO, Ru(bpy)3Cl2
10
20
60
—
60
60
60
60
43
99
z100
Trace
33
29
68
77
26
58
21
—
18
11
65
70
Trace
5
14
—
—
—
6
8
2
10
32
—
—
—
—
—
3
16
—
—
—
—
—
4c
5
6
7d
8e
—
—
a
B12-PIL/rGO ¼ 3 mg, [DDT] ¼ 2.4 ꢃ 10ꢁ3 M, [Ru(bpy)3Cl2] ¼ 5.5 ꢃ 10ꢁ4 M, [TEOA] ¼ 0.2 M, irradiation l $ 400 nm, 50 mW cmꢁ2, distance: 10 cm.
b
DDT conversion and the product yields were determined by 1H NMR. c The reaction was kept in the dark for 60 min. d [B12] ¼ 3 mg. e PIL/rGO ¼
3 mg.
to 60 min (entry 3 in Table 1), the total yield of the didechlorinated instead of 3 mg B12-PIL/rGO (entry 7 in Table 1). When using PIL/
products increased to 78% while the DDD yield decreased to 21%. rGO instead of B12-PIL/rGO in the presence of Ru(bpy)3Cl2 (entry 8
The reaction did not proceed under dark conditions (entry 4 in in Table 1), the DDT conversion reached 77% with DDD as the
Table 1). When only Ru(bpy)3Cl2 or B12-PIL/rGO (entries 5 and 6 in single product aer 60 min of irradiation. This result indicated
Table 1) was used, the DDT conversion rates were 33 and 29% that rGO which has excellent electroconductivity32 could transfer
respectively. In contrast to the result for the hybrid system (entry electrons to DDT and reduce it to DDD aer it accepted electrons
2+
3), the conversion rate of DDT was 68% and no didechlorinated from the photosensitizer Ru(bpy)3 under visible light irradia-
products were obtained even aer 60 min of irradiation when tion.33 At the same time, the fact that no didechlorinated products
a mixture of the B12 derivative ([(CN)(H2O)Cob(III)7COOH]Cl) and were obtained without B12 in the hybrid fully proved that B12 was
Ru(bpy)3Cl2 was used, where 3 mg B12 catalyst was directly used essential for didechlorination.
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It is well known that removing the second chlorine atom is concentration of DDT and DDD on the surface of B12-PIL/rGO,
much more difficult than the rst one from DDT molecules. accelerated the dechlorination reactions of DDT and DDD.
According to the literature, for B12-based photocatalysts, B12-
According to the literature,31,35 a plausible mechanism of this
BVIm-Ru copolymer7 and B12-HAS articial enzyme,34 which are catalytic system is shown in Fig. 10. Firstly, the photosensitizer
comparable to that used in this work, although they all showed Ru(II)(bpy)32+ was excited by visible light irradiation, forming its
enhanced photocatalytic activities with ꢀ100% conversion of excited state Ru(II)(bpy)32+*. Then the excited species was
DDT, few didechlorinated products were detected. From the quenched by sacricial triethanolamine (TEOA) to form
above comparison, it can be concluded that the B12-PIL/rGO Ru(bpy)3+ and the obtained Ru(bpy)3+ transferred an electron to
hybrid possessed very high photocatalytic activity for DDT the rGO sheets. Subsequently, the Co(III) center of the B12 deriv-
dechlorination, especially for its didechlorination, in the pres- ative in the hybrid accepted two electrons from rGO sheets and
ence of the photosensitizer Ru(bpy)3Cl2, and the introduction of was reduced to form the Co(I) species. The supernucleophilic
rGO signicantly enhanced the reaction efficiency.
Co(I) species had a high reactivity with organic halides to induce
In order to further investigate the dechlorination process of the oxidative addition of the alkylating agents to the metal center
DDT and the role of rGO in the hybrid catalytic system, the with dehalogenation. Finally, the resulting Co(III)–alkyl complex
reaction was performed under shorter irradiation time. When proceeded to homolytic Co–C bond cleavage to form the Co(II)
the irradiation time was shortened to 10 min, DDT conversion species and an alkyl radical, which could accept a proton from
decreased obviously to 43% (entry 1 in Table 1) and the the medium or couple or rearrange to give the corresponding
didechlorinated products DDMU and TTDB (E/Z) were also products. In the catalytic system (in Fig. 10), some of the
found except DDD. This result fully proved that some DDD Ru(bpy)32+ moieties can be adsorbed reversibly on the surface of
molecules were further dechlorinated quickly once one chloride rGO due to the electrostatic interaction and weak p–p interaction
atom was removed from the structure of DDT to produce DDD between them, and thus rGO can easily accept electrons from the
catalyzed by B12 catalyst or rGO in this hybrid catalytic system. Ru complex under irradiation and subsequently rapidly transfer
Therefore, it is reasonable to deduce that this excellent catalytic them to the Co center of the B12 complex on its surface.
efficiency should be attributed to the introduction of rGO which
Furthermore, the recycled catalysis of the B12-PIL/rGO hybrid
played a very important role not only as an electron mediator catalyst was performed since it can be easily separated from the
but also as one of the catalysts catalyzing DDT dechlorination to reaction system by centrifugation. The relevant data are shown
DDD in the current system, and a synergistic effect of B12, rGO in Table 2. According to the data, the hybrid catalyst still kept
and PIL in B12-PIL/rGO, including their respective catalytic high catalytic activity in the third run under 60 min of irradia-
performance, the excellent electron transport of rGO and the tion. The recyclability of the B12-PIL/rGO hybrid catalyst at lower
Fig. 10 Proposed mechanism for DDT dechlorination.
Table 2 Recycled catalysis of B12-PIL/rGOa
Product yieldb (%)
Irradiation time
(min)
Conversion
(%)
Entry
1
Cycle
DDD
DDMS
TTDB (E/Z)
DDMU
60
1
2
3
1
2
3
100
99
98
43
41
42
21
21
21
26
25
21
14
13
13
Trace
1
16
15
15
6
5
6
32
31
30
2
3
3
2
10
Trace
a
[DDT] ¼ 2.4 ꢃ 10ꢁ3 M, [Ru(bpy)3Cl2] ¼ 5.5 ꢃ 10ꢁ4 M, [TEOA] ¼ 0.2 M, irradiation l $ 400 nm, 50 W cmꢁ2, distance: 10 cm. b DDT conversion and
1
the product yields were determined by H HMR.
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Fig. 11 EDS spectrum of B12-PIL/rGO after 3 recycles.
conversion has also been investigated under 10 min of irra-
diation (shown in Table 2). These data indicated that this
hybrid catalyst had good stability and recyclability, and kept
its catalytic activity aer 3 recycles even at lower conversion.
The recovered B12-PIL/rGO aer 3 recycles was characterized
by EDS (Fig. 11), showing that the chemical compositions of
the hybrid have no distinct change compared with the
original.
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Conclusions
A rGO-supported B12 catalyst was successfully synthesized and
its photocatalytic activity was evaluated in the presence of Ru(II)
trisbipyridine for DDT dechlorination under visible light irra-
diation. Using the catalytic system, DDT could be effectively
dechlorinated and the yield of didechlorination reached 78%
aer 1 h of visible light irradiation, which is much higher than
that of other reported photocatalytic systems. These results
indicate that rGO could act not only as an electron mediator in
the hybrid catalyst, but also as a catalyst for the dechlorination
reaction and signicantly enhance the catalytic efficiency of the
hybrid catalytic system. In addition, this hybrid catalyst is
environmentally friendly since it can be easily reused without
any loss of catalytic efficiency.
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