g-C3N4 composites with enhanced thermocatalytic and photo-Fenton activity under visible-light

Accepted Manuscript Novel magnetic BaFe12O19/g-C3N4 composites with enhanced thermocatalytic and photo-Fenton activity under visible-light Hefei Wang, Yuanguo Xu, Liquang Jing, Shuquan Huang, Yan Zhao, Minqiang He, Hui Xu, Huaming Li PII:

S0925-8388(17)30926-X

DOI:

10.1016/j.jallcom.2017.03.144

Reference:

JALCOM 41182

To appear in:

Journal of Alloys and Compounds

Received Date: 27 November 2016 Revised Date:

7 March 2017

Accepted Date: 13 March 2017

Please cite this article as: H. Wang, Y. Xu, L. Jing, S. Huang, Y. Zhao, M. He, H. Xu, H. Li, Novel magnetic BaFe12O19/g-C3N4 composites with enhanced thermocatalytic and photo-Fenton activity under visible-light, Journal of Alloys and Compounds (2017), doi: 10.1016/j.jallcom.2017.03.144. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT

Novel magnetic BaFe12O19/g-C3N4 composites with enhanced thermocatalytic and photo-Fenton activity under visible-light Hefei Wang,a Yuanguo Xu,a* Liquang Jing,a Shuquan Huang,a Yan Zhao,b Minqiang He,a* Hui Xu,b Huaming Li,b School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013, PR China.

b

Institute for Energy Research, Jiangsu University, Zhenjiang 212013, PR China. *E-mail: [email protected]; [email protected]

ABSTRACT

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In this article, a new type of magnetic BaFe12O19/g-C3N4 composite photocatalysts were successfully fabricated by combining BaFe12O19 with polymeric g-C3N4. The

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structures, morphology, optical properties and magnetic property of composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared (IR) spectra, UV-vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM) respectively. The photocatalytic performance of BaFe12O19/g-C3N4 composites were evaluated by removing Rhodamine B (RhB) and degrading tetracycline with the presence of H2O2 under visible-

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light irradiation. The optimal percentage of doped BaFe12O19 was 16.8 wt%. As well as 16.8 wt% BaFe12O19/g-C3N4 with the presence of H2O2 can keep high photocatalytic activity after four runs reaction under visible-light irradiation. The enhanced photocatalytic performance could be ascribed to the synergistic effect between BaFe12O19 and g-C3N4,

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which can facilitate photogenerated charge separation and promote the photo-Fenton process. In addition, the BaFe12O19/g-C3N4 composites have a good magnetic property.

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After the photocatalytic reaction, the recycling and collection of photocatalyst can be easily achieved. Furthermore, 16.8 wt% BaFe12O19/g-C3N4 can degrade the RhB about 56.6 % at 100 min without light irradiation, which is much significantly higher than gC3N4 and BaFe12O19. The results suggest the combination of g-C3N4 and BaFe12O19 endowed the composite with thermocatalytic degradation ability. It also indicates the synergistic effect between the g-C3N4 and BaFe12O19 play a key role in the degradation reaction. Keywords: BaFe12O19, photocatalyst, g-C3N4, thermocatalytic, magnetic.

1. Introduction

ACCEPTED MANUSCRIPT In recent years, photocatalyst technology has been applied in many fields, such as photocatalytic evolution hydrogen and oxygen, decompose organic pollutants, mitigate the greenhouse effect and so on [1-8]. Searching for efficient semiconductor photocatalysts, which can be used in the degradation of organic pollutants and water-splitting for hydrogen production is still a big challenge [9-13]. Titanium dioxide (TiO2) was the earliest investigated

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photocatalyst, which was considered as a suitable photocatalyst because of its unique physical and chemical properties, good light stability, environment friendly, cheap and so [14-17]

on

. However, its photoconversion efficiency for photocatalysis is low due to its

large band gap (3.2 eV for anatase, and 3.0 eV for rutile). It only can be activated solely by UV region [18]. As we all know, UV region makes up only ~4 % of the total incoming [19]

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solar radiation

. Hence, numerous efforts have been taken out to improve its visible-

light (43 % of total solar energy) absorption ability through different approaches,

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including chemical doping, controlling the structures and crystals and introducing defects into nanocrystals [20,21].

Graphitic carbon nitride (g-C3N4), a p-conjugated, nontoxic and abundant materials with a narrow band gap of ~ 2.7 eV, is a promising new metal-free photocatalyst [22,23,24]. Recently, g-C3N4 has been closely watched and has frequently been used as a solar

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energy conversion photocatalyst, hydrogen production and environment purification [25-29]. However, g-C3N4 still has many defects, including low specific surface area, low conductivity and high recombination rate of the photogenerated electron-holes [30]. In order to improve its performance, numerous studies have been done such as coupling g-C3N4 with metal

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oxide, metal-free material, composite oxides and noble metals. Therefore, a series of new type semiconductor materials such as ZnO/g-C3N4 [31,32], g-C3N4/BiVO4 [33], Fe2O3/g-C3N4 [34]

, Bi2WO6/g-C3N4 [35], TiO2/g-C3N4 [36], BiPO4/g-C3N4 [37], BiOBr/g-C3N4 [38], BiOI/g-C3N4 , UiO-66/g-C3N4[40] and red phosphor/g-C3N4[41] have been synthesized and used for the

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[39]

photodegradation of organic pollutants, hydrogen production as well as water splitting. However, the powder and granule photocatalyst are difficult to recovery and likely to cause secondary pollution. Hence, other new composite photocatalyst which can be separated easily need to be further studied. At present, many people have been working on the synthesis of the magnetic g-C3N4 composites photocatalyst particles. The magnetic materials can be easily separated from the degraded polluted solutions. Therefore, photocatalyst can be reused due to its regenerative property in the photocatalytic reaction. Recently, M type spinelferrites MFe2O4 (M = Zn, Ni, Co, Cu and so on) coated with g-C3N4 have been reported as magnetic photocatalyst, such as

ACCEPTED MANUSCRIPT CoFe2O4/g-C3N4 [42], g-C3N4/NiFe2O4 [43], g-C3N4/ZnFe2O4 [44] and so on. The reported composites possessed enhanced photoactivity and magnetic property. Nowadays, the BaFe12O19 has been reported and has many advantages, such as low price, excellent magnetic properties, and good corrosion resistance [45-47]. Besides, BaFe12O19 can trigger the photo-Fenton reaction in the existence of H2O2 under visible-light irradiation [48]. As we all know, there is no report on

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the combination of BaFe12O19 and g-C3N4 as magnetic photocatalyst. In order to obtain a new material, improve the photocatalytic activity of g-C3N4 as well as to separate the photocatalyst easily, BaFe12O19 was chosen to combine with g-C3N4.

In this work, we have obtained g-C3N4 and BaFe12O19/g-C3N4 magnetic photocatalyst

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via a calcination method. The surface characteristics, crystal structure, magnetic properties and optical properties of BaFe12O19/g-C3N4 composite photocatalyst have been characterized by TEM, XRD, VSM and DRS, respectively. In order to investigate the photocatalytic

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activity of BaFe12O19/g-C3N4 composites with different mass fraction of BaFe12O19, Rhodamine B (RhB) was chosen as the target pollutants. The degradation efficiency of RhB can reach 95.8 % in 100 min by the BaFe12O19/g-C3N4 composite photocatalyst with 0.5 mL H2O2 under visible-light irradiation. Furthermore, BaFe12O19/g-C3N4 composites have a good stability and magnetic properties. After four runs reaction, BaFe12O19/g-C3N4 can not only

2 Experimental

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maintain a high photocatalytic activity, but also can be separated easily.

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2.1 Prepared of g-C3N4 and BaFe12O19/g-C3N4 composites catalyst The g-C3N4 was synthesized by calcination method under the condition of 540oC

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in the tube furnace. The specific synthesis process is as follows: a certain amount of dicyandiamide was put into the alumina crucible, then the tube furnace was heated to 350oC in 2 h, and heated preservation for 2 h. Subsequently, the resultant was heated to 540oC in 1 h and then kept for another 1 h. The whole process was completed under N2protection [49]. Finally, the product g-C3N4 was obtained. BaFe12O19 was obtained from Sinopharm Chemical Reagent Co., Ltd (Shanghai, China). The BaFe12O19/g-C3N4 composites catalyst was synthesized through the following process: 0.2 g g-C3N4 and a different mass of BaFe12O19 were uniformly mixed by grinding in an agate mortar at least 20 min. Afterwards, the mixture was placed in an alumina crucible and calcined for 4 h in the tube furnace under the temperature of 400oC.

ACCEPTED MANUSCRIPT The mass fraction of BaFe12O19 in BaFe12O19/g-C3N4 were identified as 10.1 %, 16.8 %, 24.9 % and 35.5 %, respectively, according to the thermogravimetry (TG) results. The different mass ratio of BaFe12O19 in the BaFe12O19/g-C3N4 was labeled as BaFe12O19/gC3N4 (x = 10.1, 16.8, 24.9, 35.5 wt%), x refers to the mass ratio of BaFe12O19 in the hybrids.

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2.2 Characterization

The as-prepared samples were characterized by X-ray diffraction (XRD) using a Bruker D8 diffractometer with Cu Ka radiation (λ=1.5418 Å) in the range of 2θ = 10° to 80°. The morphology of samples was studied by the transmission electron microscopy

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(TEM, JEOL-JEM-2010, JEOL, Japan). The infrared (IR) spectrum of all of the catalysts (KBr pellets) were obtained on a Nicolet Model Nexus 470FT-IR spectrometer with the

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KBr pellet technique. The UV-vis diffuse reflectance spectra (DRS) of the samples were recorded on a Shimadzu UV-2450 UV-vis spectrophotometer (Shimadzu Corporation, Japan). X-ray photoelectron spectroscopy (XPS) was conducted using an ESCA Lab MKII X-ray photoelectron spectrometer using Mg Ka radiation. The magnetic property of BaFe12O19 and BaFe12O19/g-C3N4 composites were detected by a vibrating sample field of ± 2 T.

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magnetometer (VSM) (Quantum Design Corporation, USA) with a maximum applied

2.3 Photocatalytic activity detection

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The photocatalytic reaction of BaFe12O19, g-C3N4 and different proportions of BaFe12O19/g-C3N4 composites was completed through the degradation of Rhodamin B (RhB) solution under visible-light irradiation. 70 mg of photocatalyst was added into 70

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mL of RhB (10 mg/L) in a Pyrex photocatalytic reactor connected to a circulating water system, which could keep the reaction temperature at 30oC. First of all, to insure the adsorption-desorption equilibrium between the reaction substrate solution and the photocatalyst, the hybrid was stirred for 0.5 h in the dark. Second, 0.5 mL of 30 % H2O2 was added to the mixture, and then the light was open. A sample was taken every 20 min for the centrifugal and determined the absorbance by UV-Vis spectrophotometer at 553 nm.

3. Results and discussion

ACCEPTED MANUSCRIPT 3.1 TG analysis In order to study the thermostability of the as-prepared photocatalyst and further confirm the actual ratio of BaFe12O19 and g-C3N4 in the photocatalyst, TG analysis has been accomplished from 20oC to 800oC under the condition of the air. The results are shown in Fig. 1, the mass of the pure BaFe12O19 almost unchanged from 20oC to 800oC,

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which suggests the pure BaFe12O19 have a very good thermostability. Some early research work has been reported that the unmixed g-C3N4 has two weight loss area. The first area is from 100oC to 400oC, which can be ascribed to the loss of the absorption of air and water. The second area is from 550oC to 800oC, which is due to the pyrogenic decomposition

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of g-C3N4 [50]. For the BaFe12O19/g-C3N4 composites, a bit of weight loss occurred from 100oC to 480oC, which might be due to the adsorption of air and water on the surface of

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the photocatalyst. The weight of the BaFe12O19/g-C3N4 composites quickly reduced from 530oC to 600oC, which might be attributed to the pyrogenic decomposition of g-C3N4. The decomposition temperature of g-C3N4 in the composites is lower than that of pure gC3N4 [51]. This should be ascribed to the introduction of BaFe12O19, which can decompose the g-C3N4 at a lower temperature. The same results have been reported in other papers [52,53]

. On the basis of the TG results, the exact mass fraction of BaFe12O19 in the

35.5 wt%, respectively.

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BaFe12O19/g-C3N4 composites were determined to be 10.1 wt%, 16.8 wt%, 24.9 wt% and

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20 10.1wt% BaFe O /g-C N 12 19 3 4 0

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Fig. 1. TG thermo-grams for heating the pure BaFe12O19 and the BaFe12O19/g-C3N4 composites from 20oC to 800oC. 3.2 XRD analysis The crystalline structure, pure phase and crystallite size of the synthesized g-C3N4 and BaFe12O19/g-C3N4 composites were characterized and analyzed via XRD. Fig. 2 shows

ACCEPTED MANUSCRIPT the diffraction pattern of the pure BaFe12O19, the g-C3N4 and the BaFe12O19/g-C3N4 composites crystal phase. All of the diffraction characteristic peaks of pure BaFe12O19 are assigned to spinel-type BaFe12O19 (JCPDS No. 07-0276)

[54]

. In XRD patterns of the g-

C3N4, the peaks at 2θ = 13.1° and 27.4° can be indexed as the (100) and (002) diffraction planes of g-C3N4, which associate with the interplanar structural packing and graphitic

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stacking, respectively [55,56]. From the patterns of BaFe12O19/g-C3N4 composites, it can be seen that all diffraction peaks of BaFe12O19/g-C3N4 composites are consistent with the diffraction peaks of the g-C3N4 and the pure BaFe12O19. It indicates that no impurities generated and no peak shift occurred for BaFe12O19. Besides, with enhancing the mass

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fraction of the BaFe12O19, the characteristic peaks of g-C3N4 are become weaker. This may be due to the high BaFe12O19 content in the sample covering on the surface of the gC3N4. These results show that the BaFe12O19 was bonded to the g-C3N4 surface rather

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than doped into the crystal lattice of the g-C3N4.

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Fig. 2. XRD patterns of (a) g-C3N4, (b) 10.1 wt% BaFe12O19/g-C3N4, (c) 16.8 wt% BaFe12O19/g-C3N4, (d) 24.9 wt% BaFe12O19/g-C3N4, (e) 35.5 wt% BaFe12O19/g-C3N4 and (f) pure BaFe12O19.

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3.3 SEM and TEM analyses The morphology and microstructure changes of the samples was characterized by

scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements. Fig. S1 is the SEM image of pure BaFe12O19 and BaFe12O19/g-C3N4 composites. From Fig. S1(A), we can see that BaFe12O19 is a lamellar structure. From Fig. S1(B-E), we can see that the morphology of several proportion of BaFe12O19/g-C3N4 composites has no obvious change. Hence, in order to get a better view the morphology of the complexes, we further performed the TEM and EDS mapping tests. Fig. 3(A) is the TEM of the pure g-C3N4. Fig. 3(B) is microstructure picture of pure BaFe12O19. As we

ACCEPTED MANUSCRIPT can see that BaFe12O19 are lamellar structure and its main dimensions is about 600-700 nm. Fig. 3(C) shows the morphology of 16.8 wt% BaFe12O19/g-C3N4 composite. It is obvious that the BaFe12O19 sheets are dispersed on the g-C3N4 surfance. That is to say BaFe12O19 and g-C3N4 were combined firmly. Combined with the XRD results, it could be confirmed that the BaFe12O19/g-C3N4 composite was successfully fabricated.

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Moreover, to confirm the existence of the BaFe12O19, SEM-EDS elemental mappings of 16.8 wt% BaFe12O19/g-C3N4 are shown in Fig. 4. The image confirms the X-ray signal from C, N, O, Ba and Fe elements, which are represented by purple, green, red, blue and yellow color, respectively. It is obvious that the Ba and Fe elements dispersed well.

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Taking into account that the Ba and Fe are the components of BaFe12O19, the combination

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of XRD spectra can confirm the dispersion of BaFe12O19 in the composite.

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Fig. 3. TEM of (A) g-C3N4, (B) BaFe12O19 and (C) 16.8 wt% BaFe12O19/g-C3N4 composites.

Fig. 4. The SEM image of 16.8 wt% BaFe12O19/g-C3N4 (A) and the corresponding EDS elemental mapping of C (B), N (C), O (D), Ba (E) and Fe (F) elements. 3.4 IR analysis

ACCEPTED MANUSCRIPT The IR spectrum of BaFe12O19, g-C3N4 and BaFe12O19/g-C3N4 photocatalysts are shown in Fig. 5. In the IR spectrum of pure g-C3N4, characteristic bands in the region ranging from 1241 to 1635 cm−1 (1241, 1319, 1409, 1558, and 1635 cm−1) are attributed to C-N stretching and C=N stretching [57,58]. The sharp peak at 808 cm−1 is attributed to the breathing vibration of the triazine units

[59,60]

. The broad absorption band around 3100

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cm−1 is also studied, this diffraction peak could attribute to the breathing mode of the adsorbed H2O molecules and terminal NH2 or NH groups at the defect sites of the aromatic ring [61,62]. In the spectra of pure BaFe12O19, the absorption peaks at 588 cm-1 and 437 cm-1 are accord with the Fe-O stretching vibration mode and Ba-O stretching

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vibration mode, respectively [63]. Both the characteristic peaks of BaFe12O19 and g-C3N4 can be found in the spectra of BaFe12O19/g-C3N4 photocatalysts, which indicates the

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presence of them in the composites.

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g-C3N4

T (%)

10.1wt% BaFe12O19/g-C3N4 16.8wt% BaFe12O19/g-C3N4 24.9wt% BaFe12O19/g-C3N4 35.5wt% BaFe12O19/g-C3N4

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BaFe12O19

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Fig. 5. IR spectra of g-C3N4, BaFe12O19/g-C3N4 composites and BaFe12O19.

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3.5 DRS analysis

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DRS were used to research the optical absorption property of the samples. As we can see from Fig. 6 that the g-C3N4 has a good absorption performance. The absorption edge is located around 450 nm. For pure BaFe12O19, it has a wider and higher absorption range from 200 nm to 800 nm, which may be due to its color is very deep. The absorption range of the BaFe12O19/g-C3N4 composites increased with the raise of BaFe12O19 content. That is to say, the introduction of the BaFe12O19 has an important influence on the absorption performance of BaFe12O19/g-C3N4 sample in the visible-light area, which may influence the photoactivity of the composites. The band gap energy of the semiconductor according to the relation: α = A((hν –Eg)n/2)/(hν). In Fig. S2 the results suggests that Eg of BaFe12O19 is about 1.70 eV. And the band gap of BaFe12O19 is close to the reported

ACCEPTED MANUSCRIPT article [48]. Furthermore, the narrow band gap of BaFe12O19 enhanced the visible-light absorption. Besides, the band gap energy of the g-C3N4 is around 2.7 eV in Fig. S2,

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which is in accordance with the reported work [42].

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Fig. 6. UV–Vis spectra of (a) g-C3N4, (b) 10.1 wt% BaFe12O19/g-C3N4, (c) 16.8 wt% BaFe12O19/g-C3N4, (d) 24.9 wt% BaFe12O19/g-C3N4, (e) 35.5 wt% BaFe12O19/g-C3N4 and (f) pure BaFe12O19 3.6 XPS analysis

The XPS data of 16.8 wt% BaFe12O19/g-C3N4 was shown in Fig. 7. From the survey spectrum (as shown in Fig. 7(a)), as we can see that the surface of BaFe12O19/g-C3N4 consist of Ba, Fe, C, O and N elements. From Fig. 7(b), as we can see that the Ba 3d XPS

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spectra have Ba 3d5/2 and Ba 3d3/2 binding energies at 780.1 eV and 794.9 eV, respectively. These data are almost the same with previous reported

[64]

. For the XPS

spectra of Fe 2p (Fig. 7(c)), the Fe 2p3/2 peak is observed at 711.7 eV and the Fe 2p1/2 peak is observed at 724.9 eV. These results are very close to the previously reported data [65]

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. Fig. 7(d) shows the XPS spectrum of C 1s. It has a peak at 284.9 eV, which is due to

the extraneous C. Another peak at 288.0 eV, which is proved as a C-N-C coordination in

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g-C3N4 [66]. Fig. 7(e) shows two main peaks of O 1s with the binding energies of 532.2 eV and 529.8 eV, which are assigned to the surface -OH of water molecules and the lattice oxygen of BaFe12O19, respectively[67,65]. The peak of N 1s (Fig. 7(f)) located at 398.7 eV, which had a slight deviation compared with g-C3N4 (at 398.20 eV). The result suggests that the chemical environment of N in the BaFe12O19/g-C3N4 has been changed. This means that the interaction between g-C3N4 and BaFe12O19 existed further confirmed the coexistence of g-C3N4 and BaFe12O19.

[51]

. The data of XPS

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Fig. 7. XPS spectra of 16.8 wt% BaFe12O19/g-C3N4 composite materials (a) survey of the sample, (b) C1s, (c) Ba 3d, (d) Fe 2p, (e) O1s and (f) N1s. 3.7 Analysis of Vibrating Sample Magnetometer

In order to study the magnetic property of the magnetic photocatalytic materials, the VSM of pure BaFe12O19 and 16.8 wt% BaFe12O19/g-C3N4 composites are shown in Fig. 8. The X-axis represents the applied magnetic field H and Y-axis represents magnetization

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M. As we can see from the diagram, the saturation magnetization Ms of pure BaFe12O19 and 16.8 wt% BaFe12O19/g-C3N4 composite was about 62.0 emu g-1 and 9.8 emu g-1, respectively. It is obvious that the saturation magnetization of 16.8 wt% BaFe12O19/gC3N4 composite serious lower than of pure BaFe12O19. This situation may be due to the

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reason that the introduction of the BaFe12O19 mass fraction is much smaller than the nonmagnetic g-C3N4 mass fraction. But in spite of this, the magnetic of the photocatalysts

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is sufficiently strong for separate the photocatalyst from the reaction substrate solution

Magnetization (emu/g)

under the condition of adding an external magnetic field, as shown in Fig. 8 (inside). 80 BaFe12O19

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/g-C3N4

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3.8 Photocatalytic properties and cycling experiment Fig. 9 shows the photodegradation curves of Rhodamine B (RhB) with different types of

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photocatalysts under visible-light irradiation. As we can see that (1) from the blank experiment (Fig. 9(a)), the concentration of RhB remained unchanged after 100 min, illustrating that RhB is very stable and its photolysis could be ignored without catalysts under visible-light irradiation. (2) As shown in Fig. 9(b), RhB only could be slightly

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degraded by H2O2 under visible-light irradiation. (3) As can be seen in Fig. 9(c), RhB can be decolorized by BaFe12O19 assist with 0.5 mL H2O2 up to 22.5 % in 100 min. That is to say, BaFe12O19 can decompose H2O2 under the visible-light irradiation. The similar [48]

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conclusion has also been confirmed in other work

. Furthermore, as shown in Fig. 9,

the mass fraction of BaFe12O19 has a great effects on the photocatalytic abilities of BaFe12O19/g-C3N4 composites. When the mass fraction of BaFe12O19 is 10.1 wt%, it can degrade RhB up to 66.2 % in 40 min under visible-light irradiation. When the mass fraction of BaFe12O19 is 16.8 wt%, it might degrade RhB up to 85.8 %. When the mass

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percent of BaFe12O19 was further increased up to 24.9 wt% and 35.5 wt%, the photocatalytic activity of BaFe12O19/g-C3N4 composite decreased. They can degrade RhB up to 78.7 % and 71.9 %, respectively. As we can see from the above results, the photocatalytic ability 16.8 wt% BaFe12O19/g-C3N4 is the best. In addition, the

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photocatalytic ability of the g-C3N4 was also tested in the same condition. It can degrade RhB up to 53.9 % in 40 min under visible-light irradiation. The result indicates that

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introducing a proper amount of BaFe12O19 is beneficial for the improvement of the photoactivity.

Moreover, , tetracycline as a colorless organic pollutant was used as a reaction

substrate for further evaluation of the photodegradation efficiency of 16.8 wt% BaFe12O19/g-C3N4 photocatalyst (showed in Fig. 10). According to Fig. 10, it can be seen that the main absorption peak of tetracycline (357 nm) decreases with extension of the exposure time, which indicates tetracycline can be degraded by 16.8 wt% BaFe12O19/gC3N4 photocatalyst under visible-light irradiation. To further research the recyclability of the BaFe12O19/g-C3N4 composite, the cycling experiments of 16.8 wt% BaFe12O19/g-C3N4 composite was carried out. As shown in Fig.

ACCEPTED MANUSCRIPT 11, after four recycles reaction, RhB still can be degraded up to 91.0 %. The result suggests the BaFe12O19/g-C3N4 composites have a well photostability. The separation of substrate solution and photocatalyst after cycling reaction was achieved with the addition of an external magnet field.

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Fig. 9. Photocatalytic performance of samples (a) RhB blank, (b) RhB + 0.5 mL H2O2,(c) BaFe12O19 + 0.5 mL H2O2, (d) g-C3N4 + 0.5 mL H2O2, (e) 10.1 wt% BaFe12O19/g-C3N4 + 0.5 mL H2O2, (f) 16.8 wt% BaFe12O19/g-C3N4 + 0.5 mL H2O2, (g) 24.9 wt% BaFe12O19/g-C3N4 + 0.5 mL H2O2 and (h) 35.5 wt% BaFe12O19/g-C3N4 + 0.5 mL H2O2. 0 min(dark) 20 min 40 min 60 min 80 min 100 min

0.8 0.6 0.4

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Absorbance

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0.2

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400

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Fig. 10. UV−vis absorption spectral changes for tetracycline degradation with 16.8 wt% BaFe12O19/g-C3N4/H2O2/vis system. 100 80 60 40 20 0

1

2

3

4

Number of runs

Fig. 11. Cycling runs of 16.8 wt% BaFe12O19/g-C3N4 composite. 3.9 PL spectra analysis

ACCEPTED MANUSCRIPT The photoluminescence (PL) spectra are usually used to investigate the migration, transfer, and recombination processes of the photo-generated electron and hole in a semiconductor. For study the charge transfer in the BaFe12O19/g-C3N4 hybrids, we had obtained the PL images of g-C3N4, 16.8 wt% BaFe12O19/g-C3N4 and pure BaFe12O19 excited by 365 nm. As we can see from Fig. 12, the main emission peak of pure g-

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C3N4 was centered at about 456 nm, which was consistent with the reported work [68]. And that the PL intensity of 16.8 wt% BaFe12O19/g-C3N4 hybrids was much lower than that of the pure g-C3N4, which indicated that the photo-generated charges recombination rate in 16.8 wt% BaFe12O19/g-C3N4 hybrids is much lower than that of

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the pure g-C3N4. That is, the recombination of photo-generated electron−hole pairs was highly inhibited by the introduction of BaFe12O19, which revealed photogenerated electron−hole pair separation efficiency of the 16.8 wt% BaFe12O19/g-C3N4 hybrids

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was indeed higher than that in pure g-C3N4.

Intensity (a.u.)

a

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b c

400

500

600

Wavelength (nm)

700

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Fig. 12. Spectra (PL) of (a) g-C3N4, (b) 16.8 wt% BaFe12O19/g-C3N4, (c) pure BaFe12O19.

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3.10 mechanism analysis

In order to study the mechanism of the photocatalytic activity reaction, the control

experiments under different conditions were designed. From Fig. 13(A), a mechanical mixing experiment of g-C3N4 and BaFe12O19 with BaFe12O19 content of 16.8 wt% (percentage of mixture) in the existence of 0.5 mL H2O2 was taken out for comparison. As we can see that the activity of the mechanical mixture is lower than that of 16.8 wt% BaFe12O19/gC3N4 composite. The result suggests that there is an interaction between g-C3N4 and BaFe12O19. That is beneficial for improving the photocatalytic activity. Fig. 13(B) reveals the contrast experiment that the H2O2 was not added. It can be seen that that g-C3N4 and 16.8 wt% BaFe12O19/g-C3N4 could degrade RhB up to 30.0 % and 6.7 % without H2O2,

ACCEPTED MANUSCRIPT suggesting that the H2O2 plays an significant role in the photocatalytic reaction system. As previously reported, BaFe12O19 has a good property in using H2O2 to produce hydroxyl radical, which has surmised that the surface of BaFe12O19 has a photo-Fenton reaction

[48]

. A contrast experiment without light irradiation was achieved, as shown in

Fig. 13(C), as we can see that RhB could not be degraded by H2O2 in dark condition

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without photocatalysts. It also can be seen that the degradation activities of g-C3N4 and BaFe12O19 can be neglected without light irradiation, while the 16.8 wt% BaFe12O19/gC3N4 can degrade the RhB about 56.6 % at 100 min without light irradiation in the presence of H2O2. The result is much better than g-C3N4 and BaFe12O19. Suggesting the

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combination of g-C3N4 and BaFe12O19 endowed the composite with thermocatalytic degradation ability. It also indicates that the synergistic effect between the g-C3N4 and BaFe12O19 play a very important role in the degradation reaction. It can be used as a CoFe2O4/g-C3N4

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thermocatalytic degradation system, which is not found in previous works, such as [42]

[43]

, g-C3N4/NiFe2O4

and g-C3N4/ZnFe2O4

[44]

. Therefore, the

degradation reaction can be thought as a combination of thermocatalytic and photo-Feton reaction. (A) 1.0 0.8

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mixture (0.0117g BaFe12O19 +0.0583g g-C3N4)

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Fig. 13. The control experiments: (A) photocatalytic capability of mixture and 16.8 wt% BaFe12O19/g-C3N4 composites. (B) Photocatalytic capability of g-C3N4 and 16.8 wt% BaFe12O19/g-C3N4 composites in the absence of H2O2. (C) Catalytic capability of g-C3N4, pure BaFe12O19 and 16.8 wt% BaFe12O19/g-C3N4 composites without light irradiation. According to these results, the possible reaction mechanism was put forward. It

is well known that the efficient separation of photo-generated electron-hole pairs is very important to improve the degradation activity of catalysts

[69]

. When BaFe12O19

was introduced into g-C3N4, BaFe12O19 and g-C3N4 are closely combined together and further formed a composite. Scheme 1 shows the energy position and the schematic diagram of the photocatalytic reaction process of BaFe12O19/g-C3N4 composites in the presence of H2O2. The CB and VB of BaFe12O19 are calculated to be + 0.42 eV and +

ACCEPTED MANUSCRIPT 2.12 eV according to Mulliken electronegativity theory: ECB= X − EC− 0.5(Eg), where X is the semiconductor's electronegativity and Ec is the energy of the free electron on the hydrogen scale. On the other hand, the CB and VB edge potentials of g-C3N4 were at −1.13 eV and +1.57 eV, respectively [55]. Obviously, both BaFe12O19 and g-C3N4 are excited by visible-light irradiation, and the photogenerated electrons and holes are in

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their conduction band (CB) and valence band (VB), respectively. Then, the photogenerated electron transfer from the CB of g-C3N4 to the CB of BaFe12O19 and holes on the VB of BaFe12O19 transferred to the VB of g-C3N4. This process could lead to the redistribution of photogenerated electron−hole pairs and improve the efficient separation of electron and hole and inhibit the recombination of photogenerated

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charge. As we all know, the hydroxyl radicals (•OH), superoxide radicals (•O2¯ ) and photogenrated holes (h+) are the main active radicals in the photocatalytic process.

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Valero-Luna et al. [48], studied the Vis/BaFe12O19 and Vis/BaFe12O19/H2O2 systems. In the present work, when the H2O2 is added, a photo-Fenton system Vis/BaFe12O19/gC3N4/H2O2 is created. The photogenerated electrons can react with the surface chemisorbed molecular oxygen to generate the superoxide radicals (•O2¯ ), which can be further reacted with H+ form H2O2. Finally, H2O2 can react with the photogenerated

H2O2 + e¯

•

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electrons to generate •OH, which has a significant role in degrading RhB. OH + OH¯

(3)

In addition, the photogenerated holes on the VB of g-C3N4 can not reaction with

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OH¯ or H2O to generate •OH, they can directly reaction with RhB adsorbed on the

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surface of the catalyst [70].

Scheme 1. Diagram of the energy position and photogenerated electron–hole pair transfers between BaFe12O19 and g-C3N4. According to the above results, we can know that BaFe12O19 or g-C3N4 can not degrade RhB in the presence of H2O2 under dark. Therefore, it can be deduced that

ACCEPTED MANUSCRIPT the Fe3+ did not react with H2O2 to produce •OH. When the BaFe12O19 combines with g-C3N4, the BaFe12O19/g-C3N4 composite can degrade the RhB about 56.6 % at 100 min without light irradiation in the presence of H2O2. Furthermore, we know that the surface of the g-C3N4 is negatively charged[71]. In addition, BaFe12O19 is distributed over the surface of the g-C3N4 and the interaction exists in the surface of BaFe12O19

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and g-C3N4. Thus, a possible mechanism (in the presence of H2O2 and without light irradiation) was proposed on the basis of the above conclusions. Scheme 2 shows the process of the activation of H2O2 by the BaFe12O19/g-C3N4 composite catalyst without light. The holes of BaFe12O19 is attracted by the g-C3N4 due to its surface is negatively charged and the electrons of BaFe12O19 are exposed to the surface of the composite.

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Thus, H2O2 can react with e¯ and then decomposed to generate •OH radicals, which can

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degrade RhB due to its high oxidation ability.

Scheme 2. The thermocatalytic reaction process of BaFe12O19/g-C3N4 composites. For confirming the main active species, the trapping experiments of radicals using disodium ethylenediamine tetraacetate (EDTA-2Na), tert butyl alcohol (TBA) and 1,4-

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benzoquinone (BQ) to capture hole (h+), hydroxyl radical (•OH) and superoxide radical (•O2¯ ), respectively. It is obvious in Fig. 14 that the addition of three species of trapping

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agents caused an inhibition to the RhB degradation efficiency. This result show that the main active species should be •OH, h+ and •O2¯ during the photocatalytic reaction. 1.4

+1 mM EDTA-2Na +5 mL TBA +0.05 mM BQ 16.8wt% BaFe12O19/g-C3N4

1.2

C/C0

1.0 0.8 0.6 0.4 0.2 0.0 0

20

40

60

80

100

Time(min)

Fig. 14. Trapping experiments of active species in the photocatalytic process.

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4. Conclusions In conclusion, a magnetic photocatalyst BaFe12O19/g-C3N4 have been successfully fabricated by a simple calcination method. BaFe12O19/g-C3N4 possessed the thermocatalytic and photo-Feton ability to decompose pollutant. The 16.8 wt% BaFe12O19/g-C3N4 composite

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showed the high performance, which can degrade RhB up to 95.8 % and 56.6% in 100 min under visible-light irradiation and without light irradiation. In addition, 16.8 wt% BaFe12O19/g-C3N4 can degrade tetracycline under visible-light irradiation. This is mainly due to the synergistic effect between BaFe12O19 and g-C3N4. In addition, BaFe12O19/g-C3N4 composites have strong magnetic properties, which caused BaFe12O19/g-C3N4 composites can

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easily be separated from the reaction solution after cycling reactions. The work presents a straightforward procedure for synthesis of magnetic BaFe12O19/g-C3N4 composites, which is photocatalytic activity and magnetism.

Acknowledgements

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believed to be a promising photocatalyst in the environmental applications due to its good

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References

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This work is financially supported by the National Natural Science Foundation of China for Youths (No. 21407065), Natural Science Foundation of Jiangsu Province for Youths (BK20140533), China Postdoctoral Science Foundation (2015T80514, 2016M591777). Jiangsu University Scientific Research Funding (No. 14JDG052). A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education.

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[1] M.R. Hoffmann, S.T. Martin, W. Choi, D.W. Bahnemann, Environmental applications of semiconductor photocatalysis, Chem. Rev. 95 (1995) 69-96. [2] A. Kudo, Y. Miseki, Heterogeneous photocatalyst materials for water splitting, Chem. Soc. Rev. 38 (2009) 253-278. [3] R. Afeesh, N.A.M. Barakat, S.S. Al-Deyab, A. Yousef, H.Y. Kim, Nematic shaped cadmium sulfide doped electrospun nanofiber mat: highly efficient, reusable, solar light photocatalyst, Colloids Surf. A: Physicochem. Eng. Aspects 409 (2012) 21-29. [4] T.J. Chen, W. Quan, L.B. Yu, Y.Z. Hong, C.J. Song, M.S. Fan, L.S. Xiao, W. Gu, W.D. Shi, One-step synthesis and visible-light-driven H2 production from water splitting of Ag quantum dots/g-C3N4 photocatalysts, J. Alloys Compd. 686 (2016) 628634. [5] Y.R. Smith, K.J.A. Raj, V.(Ravi) Subramanian, B. Viswanathan, Sulfated Fe2O3-TiO2 synthesized from ilmenite ore: a visible-light active photocatalyst, Colloids Surf. A: Physicochem. Eng. Aspects 367 (2010) 140-147.

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

[6] X.M. Hou, Y.L. Tian, X. Zhang, S.L. Dou, L. Pan, W.J. Wang, Y. Li, J.P. Zhao, Preparation and characterization of Fe3O4/SiO2/Bi2MoO6 composite as magnetically separable photocatalyst, J. Alloys Compd. 638 (2015) 214-220. [7] S. Martha, P.C. Sahoo, K.M. Parida, An overview on visible light responsive metal oxide based photocatalysts for hydrogen energy production, RSC Advances 5 (2015) 61535-61553. [8] J.Y. Li, X. Jiang, L. Lin, J.J. Zhou, G.S. Xu, Y.P. Yuan, Improving the photocatalytic performance of polyimide by constructing an inorganic-organic hybrid ZnO-polyimide core–shell structure, J. Mol. Catal. A-Chem. 406 (2015) 46-50. [9] J. Li, S.K. Cushing, P. Zheng, T. Senty, F. Meng, A.D. Bristow, A. Manivannan, N. Wu, Solar hydrogen generation by a CdS-Au-TiO2 sandwich nanorod array enhanced with Au nanoparticle as electron relay and plasmonic photosensitizer, J. Am. Chem. Soc. 136 (2014) 8438-8449. [10] J. Lin, A. Nattestad, H. Yu, Y. Bai, L. Wang, S.X. Dou, J.H. Kim, Highly connected hierarchical textured TiO2 spheres as photoanodes for dye-sensitized solar cells, J. Mater. Chem. A 2 (2014) 8902-8909. [11] J. Tian, Y. Sang, Z. Zhao, W. Zhou, D. Wang, X. Kang, H. Liu, J. Wang, S. Chen, H. Cai, Enhanced photocatalytic performances of CeO2/TiO2 nanobelt hetero- structures, Small 9 (2013) 3864-3872. [12] J. Tian, Z. Zhao, A. Kumar, R.I. Boughton, H. Liu, Recent progress in design, synthesis and applications of one-dimensional TiO2 nanostructured surface heterostructures: a review, Chem. Soc. Rev. 43 (2014) 6920-6937. [13] Z. Zhao, J. Tian, Y. Sang, A. Cabot, H. Liu, Structure synthesis and applications of TiO2 nanobelts, Adv. Mater. 27 (2015) 2557-2582. [14] Y.H. Ng, I.V. Lightcap, K. Goodwin, M. Matsumura, P.V. Kamat, To what extentdo graphene scaffolds improve the photovoltaic and photocatalytic response of TiO2 nanostructured films?, J. Phys. Chem. Lett. 1 (15) (2010) 2222-2227. [15] P.V. Kamat, TiO2 nanostructures: recent physical chemistry advances, J. Phys. Chem. C 116 (2012) 11849-11851. [16] K.X. Li, T. Chen, L.S. Yan, Y.H. Dai, Z.M. Huang, J.J. Xiong, D.Y. Song, Y. Lv, Z.X. Zeng, Design of graphene and silica co-doped titania composites with ordered mesostructure and their simulated sunlight photocatalytic performance towards atrazine degradation, Colloids Surf., A: Physicochem. Eng. Aspects 422 (2013) 90-99. [17] H. Zhang, X.J. Lv, Y.M. Li, Y. Wang, J.H. Li, P25-graphene composite as a high performance photocatalyst, ACS Nano 4 (2010) 380-386. [18] H. Yu, J. Pan, Y. Bai, X. Zong, X. Li, L. Wang, Hydrothermal synthesis of a crystalline rutile TiO2 nanorod based network for efficient dye-sensitized solar cells, Chem. A Eur. J. 19 (2013) 13569-13574. [19] Y.S. Fu, X. Wang, Magnetically separable ZnFe2O4 graphene catalyst and its high photocatalytic performance under visible-light irradiation, Ind. Eng. Chem. Res. 50 (2011) 7210-7218. [20] W. Zhou, Z. Yin, Y. Du, X. Huang, Z. Zeng, Z. Fan, H. Liu, J. Wang, H. Zhang, Synthesis of few-layer MoS2 nanosheet-coated TiO2 nanobelt heterostructures for enhanced photocatalytic activities, Small 9 (2013) 140-147. [21] M.N. Chong, B. Jin, C.W.K. Chow, C. Saint, Recent developments in photocatalytic water treatment technology: a review, Water Res. 44 (2010) 2997-3027. [22] X.C. Wang, K. Maeda, A. Thomas, K. Takanabe, G. Xin, J.M. Carlsson, K. Domenet, M. Antonietti, A metal-free polymeric photocatalyst for hydrogen production from water under visible-light, Nat. Mater. 8 (2009) 76-80.

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

[23] S. Patnaik, S. Martha, K.M. Parida, An overview of the structural, textural and morphological modulations of g-C3N4 towards photocatalytic hydrogen production, RSC Advances 6 (2016) 46929-46951. [24] Y.F. Guo, J. Li, Y.P. Yuan, L. Li, M.Y. Zhang, C.Y. Zhou, Z.Q. Lin, A rapid microwave-assisted thermolysis route to highly crystalline carbon nitrides for efficient hydrogen generation, Angew. Chem. Int. Ed 55 (2016) 14693-14697. [25] Y.D Hou, A.B. Laursen, J.S. Zhang, G.D. Zhang, Y.S. Zhu, X.C. Wang, S. Dahl, I. Chorkendorff, Layered nanojunctions for hydrogen-evolution catalysis, Angew. Chem. Int. Ed. 52 (2013) 3621-3625. [26] L.C. Chen, D.J. Huang, S.Y. Ren, T.Q. Dong, Y.W. Chi, G.N. Chen, Preparation of graphitelike carbon nitride nanoflake film with strong fluorescent and electrochemiluminescent activity, Nanoscale 5 (2013) 225-230. [27] Y. Wang, X.C. Wang, M. Antonietti, Polymeric graphitic carbon nitride as a heterogeneous organocatalyst: from photochemistry to multipurpose catalysis to sustainable chemistry, Angew. Chem. Int. Ed. 51 (2012) 68-69. [28] S. Martha, A. Nashim, K.M. Parida, Facile synthesis of highly active g-C3N4 for efficient hydrogen production under visible light, Journal of Materials Chemistry A 1 (2013) 7816-7824. [29] S. Patnaik, S. Martha, S. Acharya, K.M. Parida, An overview of the modification of g-C3N4 with high carbon containing materials for photocatalytic applications, Inorganic Chemistry Frontiers 3 (2016) 336-347. [30] Y.J. Zhang, T. Mori, J.H. Ye, M. Antonietti, Phosphorus-doped carbon nitride solid: enhanced electrical conductivity and photocurrent generation, J. Am. Chem. Soc. 132 (2010) 6294-6295. [31] W. Liu, M.L. Wang, C.X. Xu, S.F. Chen, Facile synthesis of g-C3N4/ZnO composite with enhanced visible-light photooxidation and photoreduction properties, Chem. Eng. J. 209 (2012) 386-393. [32] J.X. Sun, Y.P. Yuan, L.G. Qiu, X. Jiang, A.J. Xie, Y.H. Shen, J.F. Zhu, Fabrication of composite photocatalyst g-C3N4-ZnO and enhancement of photocatalytic activity under visible light, Dalton Trans. 41 (2012) 6756-6763. [33] Y.X. Ji, J.F. Cao, L.Q. Jiang, Y.H. Zhang, Z.G. Yi, g-C3N4/BiVO4 composites with enhanced and stable visible light photocatalytic activity, J. Alloys Compd. 590 (2014) 9-14. [34] Y. Liu, Y.X. Yu, W.D. Zhang, Photoelectrochemical study on charge transfer properties of nanostructured Fe2O3 modified by g-C3N4, Int. J. Hydrogen Energy 39 (2014) 9105-9113. [35] Y.L. Tian, B.B. Chang, J.L. Lu, J. Fu, F.N. Xi, X.P. Dong, Hydrothermal synthesis of graphitic carbon nitride-Bi2WO6 heterojunctions with enhanced visible-light photocatalytic activities, ACS Appl. Mater. Interfaces 5 (2013) 7079-7085. [36] C. Wang, W.S. Zhu, Y.H. Xu, H. Xu, M. Zhang, Y.H. Chao, S. Yin, H.M. Li, J.G. Wang, Preparation of TiO2/g-C3N4 composites and their application in photocatalytic oxidative desulfurization, Ceram. Int. 40 (2014) 11627-11635. [37] C. Pan, J. Xu, Y. Wang, D. Li, Y. Zhu, Dramatic activity of C3N4/BiPO4 photocatalyst with core/shell structure formed by self-assembly, Adv. Funct. Mater. 22 (2012) 1518-1524. [38] L.Q. Ye, J.Y. Liu, Z. Jiang, T.Y. Peng, L. Zan, Facets coupling of BiOBr-g-C3N4 composite photocatalyst for enhanced visible-light-driven photocatalytic activity, Appl. Catal. B, 142 (2013) 1-7.

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

[39] C. Chang, L. Zhu, S. Wang, X. Chu, L. Yue, Novel mesoporous graphite carbon nitride/BiOI heterojunction for enhancing photocatalytic performance under visible-light irradiation, ACS Appl. Mater. Interfaces 6 (2014) 5083-5093. [40] R. Wang, L.N. Gu, J.J. Zhou, X.L. Liu, F. Teng, C.H. Li, Y.H. Shen, Y.P. Yuan, Quasi-polymeric metal-organic framework UiO-66/g-C3N4 heterojunctions for enhanced photocatalytic hydrogen evolution under visible light irradiation, Adv. Mater. Interfaces 2 (2015) 1500037. [41] Y.P. Yuan, S.W. Cao, Y.S. Liao, L.S. Yin, C. Xue, Red phosphor/g-C3N4 heterojunction with enhanced photocatalytic activities for solar fuels production, Appl. Catal. B. Environ. 140-141(2013) 164-168. [42] S.Q. Huang, Y.G. Xu, M. Xie, H. Xu, M.Q. He, J.X. Xia, L.Y. Huang, H.M. Li, Synthesis of magnetic CoFe2O4/g-C3N4 composite and its enhancement of photocatalytic ability under visible-light, Colloids Surf., A: Physicochem. Eng. Aspects 478 (2015) 71-80. [43] H.Y. Ji, X.C. Jing, Y.G Xu, J. Yan, H.P. Li, Y.P Li, L.Y. Huang, Q. Zhang, H. Xu, H.M. Li, Magnetic g-C3N4/NiFe2O4 hybrids with enhanced photocatalytic activity, RSC Adv. 5 (2015) 57960-57967. [44] S.W. Zhang, J.X. Li, M.Y. Zeng, G.X. Zhao, J.Z. Xu, W.P. Hu, X.K. Wang, In situ synthesis of water-soluble magnetic graphitic carbon nitride photocatalyst and its synergistic catalytic performance, ACS Appl. Mater. Interfaces 5 (2013) 12735-12743. [45] A. Drmota, M. Drofenik, A. Znidarsic, Synthesis and characterization of nano-crystalline strontium hexaferrite using the coprecipitation and microemulsion methods with nitrate precursors, Ceram. Int. 38 (2012) 973-979. [46] M.J. Molaei, A. Ataie, S. Raygan, S.J. Picken, E. Mendes, F.D. Tichelaar, Synthesis and characterization of BaFe12O19/Fe3O4 and BaFe12O19/Fe/Fe3O4 magnetic nano-composites, Powder Technol. 221 (2012) 292-295. [47] M.M. Rashad, M. Radwan, M.M. Hessien, Effect of Fe/Ba mole ratios and surface-active agents on the formation and magnetic properties of co-precipitated barium hexaferrite, J. Alloys Compd. 453 (2008) 304-308. [48] C. Valero-Luna, S.A. Palomares-Sanchez, F. Ruiz, Catalytic activity of the barium hexaferrite with H2O2/visible-light irradiation for degradation of Methylene Blue, Catal. Today 266 (2016) 110-119. [49] T. Zhou, Y.G. Xu, H. Xu, H.F. Wang, Z.L. Da, S.Q. Huang, H.Y. Ji, H.M. Li, In situ oxidation synthesis of visible-light-driven plasmonic photocatalyst Ag/AgCl/gC3N4 and its activity, Ceram. Int. 40 (2014) 9293-9301. [50] Y.G. Xu, M. Xie, S.Q. Huang, H. Xu, H.Y. Ji, J.X. Xia, Y.P. Li, H.M. Li, High yield synthesis of nano-size g-C3N4 derivatives by a dissolve-regrowth method with enhanced photocatalytic ability, RSC Adv. 5 (2015) 26281-26290. [51] Y.G. Xu, H. Xu, J. Yan, H.M. Li, L.Y. Huang, J.X. Xia, S. Yin, H.M. Shu, A plasmonic photocatalyst of Ag/AgBr nanoparticles coupled withg-C3N4 with enhanced visible-light photocatalytic ability, Colloids Surf., A: Physicochem. Eng. Aspects 436 (2013) 474-483. [52] P. Niu, G. Liu, H.M. Cheng, Nitrogen vacancy-promoted photocatalytic activity of graphitic carbon nitride, J. Phys. Chem. C 116 (2012) 11013-11018. [53] L.Y. Huang, H. Xu, Y.P. Li, H.M. Li, X.N. Cheng, J.X. Xia, Y.G. Xu, G.B. Cai, Visible-light-induced WO3/g-C3N4 composites with enhanced photocatalytic activity, Dalton Trans. 42 (2013) 8606-8616. [54] N. Gholamreza, G. Davood, Y. Asieh, S. Minoo, A sonochemical-assisted method for synthesis of BaFe12O19 nanoparticles and hard magnetic nanocomposites, J. Ind. Eng. Chem. 20 (2014) 3425-3429.

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[55] H. Xu, J. Yan, Y.G. Xu, Y.H. Song, H.M. Li, J.X. Xia, C.J. Huang, H.L. Wan, Novel visible-light-driven AgX/graphite-like C3N4 (X = Br, I) hybrid materials with synergistic photocatalytic activity, Appl. Catal., B 129 (2013) 182-193. [56] J. Di, J.X. Xia, S. Yin, H. Xu, M.Q. He, H.M. Li, L. Xu, Y.P. Jiang, A gC3N4/BiOBr visible-light-driven composite: synthesis via a reactable ionic liquid and improved photocatalytic activity, RSC Adv. 3 (2013) 19624-19631. [57] X.F. Li, J. Zhang, L.H. Shen, Y.M. Ma, W.W. Lei, Q.L. Cui, G.T. Zou, Preparation and characterization of graphitic carbon nitride through pyrolysis of melamine, Appl. Phys. A: Mater. 94 (2009) 387-392. [58] M. Kim, S. Hwang, J.S. Yu, Novel ordered nanoporous graphitic C3N4 as a support for Pt-Ru anode catalyst in direct methanol fuel cell, J. Mater. Chem. 17 (2007) 1656-1659. [59] J.H. Liu, T.K. Zhang, Z.C. Wang, G. Dawson, W. Chen, Simple pyrolysis of urea into graphitic carbon nitride with recyclable adsorption and photocatalytic activity, J. Mater. Chem. 21 (2011) 14398-14401. [60] G.Q. Li, N. Yang, W.L. Wang, W.F. Zhang, Synthesis, photophysical and photocatalytic properties of N-doped sodium niobate sensitized by carbon nitride, J. Phys. Chem. C 113 (2009) 14829-14833. [61] H.J. Yan, H.X. Yang, TiO2/g-C3N4 composite materials for photocatalytic H2 evolution under visible-light irradiation, J. Alloys Compd. 509 (2011) L26-L29. [62] S.C. Yan, Z.S. Li, Z.G. Zou, Photodegradation performance of g-C3N4 fabricated by directly heating Melamine, Langmuir 25 (2009) 10397-10401. [63] Z. Wang, T.P. Comyn, M. Ghadiri, G.M. Kale, Maltose and pectin assisted sol-gel production of Ce0.8Gd0.2O1.9 solid electrolyte nanopowders for solid oxide fuel cells, J. Mater. Chem. 21 (2011) 16494-16499. [64] L.X. Wang , J. Zhang, Q.T. Zhang, N.C. Xu, J. Song, XAFS and XPS studies on site occupation of Sm3+ ions in Sm doped M-type BaFe12O19, J. Magn. Magn. Mater. 377 (2015) 362-367. [65] M. Koleva, P. Atanasov, R. Tomov, O. Vankov, C. Matin, C. Ristoscu, I. Mihailescu, D. Iorgov, S. Angelova, Ch. Ghelev, N. Mihailov, Pulsed laser deposition of barium hexaferrite (BaFe12O19) thin films, Appl. Surf. Sci. 154-155 (2000) 485-491. [66] S.C. Yan, Z.S. Li, Z.G. Zou, Photodegradation of Rhodamine B and methyl orange over boron-doped g-C3N4 under visible-light irradiation, Langmuir 26 (2010) 3894-3901. [67] Y.J. Yao, F. Lu, Y.P. Zhu, F.Y. Wei, X.T. Liu, C. Lian, S.B. Wang, Magnetic coreshell CuFe2O4@C3N4 hybrids for visible-light photocatalysis of Orange II, J. Hazard. Mater. 297 (2015) 224-233. [68] S.W. Zhang, J.X. Li, M.Y. Zeng, G.X. Zhao, J.Z. Xu, W.P. Hu, X.K. Wang, In situ synthesis of water-soluble magnetic graphitic carbon nitride photocatalyst and its synergistic catalytic performance, ACS Appl. Mater. Interfaces 5 (2013) 12735-12743. [69] M.J. Bojdys, J.O. Muller, M. Antonietti, A. Thomas, Ionothermal synthesis of crystalline, condensed, graphitic carbon nitride, Chem.Eur.J.14 (2008) 8177-8182. [70] H. Dai, S.P. Zhang, G.F. Xu, L.S. Gong, M. Fu, X.H. Li, S.Y. Lu, C.Y. Zeng, Y.W. Jiang, Y.Y. Lin, G.N. Chen, A sensitive arecoline photoelectrochemical sensor based on graphitic carbon nitride nanosheets activated by carbon nanohorns, RSC Adv.4 (2014) 11099-11102. [71] Y.G. Xu, H. Xu, L. Wang, J. Yan, H.M. Li, Y.H. Song, L.Y. Huang, G.B. Cai, The CNT modified white C3N4 composite photocatalyst with enhanced visible-light response photoactivity, Dalton Trans, 42 (2013) 7604-7613.

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Highlights The new photocatalyst BaFe12O19/g-C3N4 composites were synthesized. The BaFe12O19/g-C3N4 composites have stable magnetism. The combination of BaFe12O19 and g-C3N4 could degrade colored and colorless

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The BaFe12O19/g-C3N4 composites possess the ability of thermocatalytic degradation of

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pollutants.