- Email: [email protected]
Preparation and performance of Fe3O4@hydrophilic graphene composites with excellent Photo-Fenton activity for photocatalysis
Materials Letters 183 (2016) 61–64
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Preparation and performance of Fe3O4@hydrophilic graphene composites with excellent Photo-Fenton activity for photocatalysis Pengjun Wang, Liqiu Wang n, Qi Sun, Shaobo Qiu, Yang Liu, Xiaobo Zhang, Xuelong Liu, Lihui Zheng College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao, 066004 China
art ic l e i nf o
a b s t r a c t
Article history: Received 19 April 2016 Received in revised form 15 July 2016 Accepted 16 July 2016 Available online 18 July 2016
Composites (Fe3O4@HG) of hydrophilic graphene (HG) and Fe3O4 from an iron precursor of FeC13 6H2O and (NH4)2Fe(SO4)2 6H2O were prepared without any organic surfactants by a facile chemical co-precipitation method. Fe3O4 nanoparticles in Fe3O4@HG were about 15 nm in dimension and were ultradispersed on HG nanosheets. Fe3O4@HG exhibited paramagnetic characteristic and better stability in water. Photo-Fenton reaction results demonstrated that Fe3O4@HG composites could degrade methylorange (MO) dye with high efficiency in a short time. When the loading capacity of HG in Fe3O4@HG composites was 53.81 wt%, the catalytic efficiency could reach 87.68% after 30 min and the catalytic rate could be 0.055 mg min 1 in the first five minutes. A possible catalytic cycle for Fe3O4@HG catalyzed photo degradation of the dye was elucidated. The photo-generated electrons were transferred rapidly on the surface of HG and promoted the conversion efficiency of Fe3 þ /Fe2 þ due to the good absorption and electronic conductivity of HG. The composites would be applied as photo-catalysts for treatment of wastewater. & 2016 Elsevier B.V. All rights reserved.
Keywords: Magnetic graphene composites Hydrophilic graphene and Fe3O4 Paramagnetic characteristic Photo degradation Photo-Fenton activity
1. Introduction Applications of organic dyes in industries lead to the discharge of an amount of colored wastewater and bring environmental contaminants [1]. Advanced oxidation processes based on Fenton's reaction are successful for degradation of the contaminated water. But they suffer from the disadvantages of difficult separation and recovery for the Fe2 þ metal ions, so magnetic Fenton-like catalysts are developed. Fe3O4 has good magnetic properties and is one of the most promising Fenton-like catalysts [2]. The coexistence of Fe2 þ and Fe3 þ in Fe3O4 octahedral structure [3,4] could improve the catalytic activity of Fenton reaction and enhance degradation efficiency for the dye contaminants. But Fe3O4 nanoparticles are prone to aggregate during the Fenton process, lose dispersion stability and diminish their catalytic activity. Graphene (Gr) could prevent the aggregation of Fe3O4 nanoparticles and increase the catalytic efficiency of Fenton reaction because of excellent specific area and electrical conductivity, so it has become an ideal support used for the anchor of Fe3O4 nanoparticles and the most promising building block for photocatalysis. But the problem is that it could not composite with Fe3O4 well due to its hydrophobicity. A novel type of hydrophilic graphene (HG), which not only n
Corresponding author. E-mail address: [email protected] (L. Wang).
http://dx.doi.org/10.1016/j.matlet.2016.07.080 0167-577X/& 2016 Elsevier B.V. All rights reserved.
remained the pristine structure of Gr, but also exhibited high dispersion property in aqueous solution, was developed in our previous work [5]. In this paper, novel magnetic Fe3O4@HG composites have been developed from the HG and Fe3O4. The composites have excellent dispersion stability in water and PhotoFenton reaction catalytic activity due to the presence of the synergetic effect between the Fe3O4 nanoparticles and HG, and are expected to be applied as effective catalysts for the removal of dyes in wastewater.
2. Materials and methods 2.1. Preparation of GO and HG Graphene oxide (GO) was synthesized by the improved Hummers' method [6], and HG was prepared by GO reacting with phenylhydrazine-4-sulfonic acid at 85 °C for 12 h [5]. 2.2. Preparation of Fe3O4@HG composites 6 mL mixed iron salt (MIS) from 24 mg FeC13 6H2O and 19.2 mg (NH4)2Fe(SO4)2 6H2O in water was treated under ultrasonic for 5 min. Different volumes of 6.00 mg mL 1 HG solution were added to the MIS, adjusting the total volume of reaction solution to 25 mL by deionized water. After 5 mL strong ammonia
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P. Wang et al. / Materials Letters 183 (2016) 61–64
was added, the mixture was kept at 85 °C for 1 h under N2. Cooling the mixture naturally to room temperature, Fe3O4@HG nanoparticles were obtained by magnetic separation, washed several times with deionized water and dried at 60 °C under vacuum. As above, three types of Fe3O4@HG nanoparticles could be prepared by adding different volumes of HG solution: (a) 0.5 mL, (b) 2.0 mL and (c) 8.0 mL, and the corresponding mass fraction of HG was about 22.56 wt%, 53.81 wt% and 82.33 wt%, respectively. For comparison, Fe3O4 (d) was synthesized by the above method without HG. 2.3. Photo-Fenton reaction activity Activity of Photo-Fenton reaction of Fe3O4@HG was evaluated by the degradation of methyl-orange (MO) under 500 W high-voltage mercury lamp [3]. 3 mg of Fe3O4@HG was added into 50 mL 10 mg L 1 MO solution. After adjusting the pH value to 3.5 with 0.1 M H2SO4, the Fenton reaction was initiated by adding H2O2 (1.2 mL, 30 wt%). At the given time intervals, the analytic samples were taken from the mixture and analyzed by UV–vis spectra after they were centrifuged and filtrated by a 0.45 mm filter film. 2.4. Characterization Zetasizer Nano ZS from Malvern Instrument was used for the Zeta potential measurements. Fourier transform infrared (FT-IR) spectra were measured by using a Nicolet iS10 spectrometer. X-ray diffraction (XRD) patterns of samples were collected by using D-max-2500 XRD analysis meter with Cu Kα radiation (λ ¼0.154 nm). Transmission electron microscopic (TEM) images were obtained by using a Hitachi HT7700 transmission electron microscopy at an accelerating voltage of 100 kV. Scanning electron microscopic (SEM) images were acquired by a Hitachi S-4800 S2 field emission scanning electron microscopy. Thickness information of the samples was obtained by multimode 8 at. force microscopes (AFM). Magnetic properties of the samples were measured by vibrating sample magnetometer lake shore 7407 and the magnetic hysteresis loop was obtained by varying magnetic field between þ 20,000 and 20,000 Oe at 300 K.
3. Results and discussion Fe3O4@HG composites were characterized by TEM, AFM and SEM. As shown in Fig. 1(A) and (B), Fe3O4 nanoparticles with diameter of 15 nm in average were uniformly distributed on the surface of HG nanosheets. The inset in Fig. 1(B) revealed the
thickness of Fe3O4@HG composites was around 18 nm. Fig. 1 (C) exhibited Fe3O4 nanoparticles were assembled and grew upright with high density in the layers of HG nanosheets which effectively prevented the agglomeration of Fe3O4 nanoparticles. Fig. 2(A) showed the deformation vibration of S–O at 1178, 1125 cm 1 and S-phenyl at 1035 cm 1 attributing to the sulfonic groups of HG in Fe3O4@HG [2]. Compared to 591 cm 1 of the pristine Fe3O4, the peak at 574 cm 1 corresponding to the Fe-O stretching vibration became blue shift due to the interaction between Fe3O4 nanoparticle and HG nanosheets. Fig. 2(B) exhibited that the XRD patterns of Fe3O4@HG were similar to that of the pristine Fe3O4. The diffraction peaks at 2θ ¼30.24, 35.56, 43.24, 53.66, 57.20 and 62.82° were corresponding to the (220), (311), (400), (422), (511) and (440) reflections of standard Fe3O4 (JCPDS no.19-0629) [7]. Fig. 3(A) demonstrated that the absolute value of zeta potential (AVZP) of Fe3O4@HG composites was above 27 mv, which was greater than 19.53 mv of pristine Fe3O4. So Fe3O4@HG had better stability in water than pristine Fe3O4. Furthermore, when the loading capacity of HG was increased from 22.56 to 82.33 wt%, the AVZP of Fe3O4@HG was improved from 27.1 to 38.1 mv, and this illustrated that it was HG that promoted the dispersion of Fe3O4 nanoparticles in water. The dispersing image was also shown in the inset of Fig. 3(A). With increasing amount of HG, the dispersion of Fe3O4@HG became more stable. Fig. 3 (B) exhibited the S-like shape of magnetization curves without going through the origin point and all samples possessed paramagnetic behavior, so they could be separated easily and rapidly from their mixtures due to their fast magnetic response under an external magnetic field. When the loading capacity of HG was increased from 22.56 to 82.33 wt%, the specific saturation magnetizations of Fe3O4@HG were gradually decreased from 31.86 to 5.84 emu g 1 because the Fe3O4/HG ratio in Fe3O4@HG decreased with increasing HG, and this weakened the exhibition of magnetization of Fe3O4@HG. So the magnetic response might be controlled by the loading capacity of HG in Fe3O4@HG, and this made the separation speed of Fe3O4@HG become more flexible. In order to investigate the photocatalytic activity, Fe3O4@HG composites were applied to degrade MO by Photo-Fenton reaction. The catalytic efficiency (Ec) and catalytic rate (Rc) were calculated by the following equations:
E c( %) = A 0 −A t /A 0 × 100
(
)
R c mgmin−1 =Mc/t
(1) (2)
A0 and At were the absorbance at 465 nm of the MO samples at the initial time and different interval time t, respectively, and Mc
Fig. 1. (A) TEM and Fe3O4 size distribution, (B) AFM and its thickness and (C) SEM image of a Fe3O4@HG composite (sample b).
P. Wang et al. / Materials Letters 183 (2016) 61–64
63
Fig. 2. (A) FT-IR spectra and (B) XRD patterns.
Fig. 3. (A) Zeta potential and the dispersion image and (B) magnetization curves of the samples.
Fig. 4. (A) Catalytic efficiency and (B) Catalytic rate of the samples for degrading MO.
(mg) was the mass of MO photodegraded. Fig. 4(A) showed that Ec increased with the increasing time from 5 to 30 min. Pristine Fe3O4 had the weakest Ec (9.46%, 30 min), while samples (a), (b) and (c) demonstrated a high Ec due to the presence of HG. When the loading capacity of HG in Fe3O4@HG was 53.81 wt%, the maximum Ec could reach 87.68%. But when the content of HG increased to 82.33 wt%, the Ec decreased to 65.59%. Rc shown in Fig. 4(B) exhibited the same changing tendency with the
corresponding Ec, sample (d) had the slowest catalytic rate (0.00283 mg min 1, 5 min), and sample (b) demonstrated the largest Rc (0.055 mg min 1, 5 min). Overmuch HG in Fe3O4@HG led to the decrease of Ec and Rc, the reason might be that excess HG covered up Fe3O4 particles, made the exposed specific area of Fe3O4 particles in Fe3O4@HG reduce, and minimized the photocatalytic activity. As a result, the optimal loading capacity of HG in Fe3O4@HG for Photo-Fenton reaction activity was 53.81 wt%.
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4. Conclusions Fe3O4@HG composites were synthesized by co-precipitating methods. The Fe3O4 nanoparticles in Fe3O4@HG with average size of 15 nm were uniformly and densely tethered onto HG nanosheets. The composites demonstrated paramagnetic characteristic, better stability in water, and higher Photo-Fenton activity. The Fe3O4@HG composites would provide a promising pathway in the removal of dyes in wastewater.
Acknowledgments The authors would like to thank Hebei Natural Science Foundation (No. B2015203259) and Yanshan University Graduate Course Construction (No. SF201412) for providing the financial support for this project. Fig. 5. The Photo-Fenton catalytic cycle of Fe3O4@HG.
References Pristine Fe3O4 exhibited the weakest Photo-Fenton reaction activity because of the deposition of Fe(OH)3 formed during the photocatalytic process, while Fe3O4@HG could limit the formation of Fe(OH)3 due to the rapid reduction of Fe3 þ into Fe2 þ . Fig. 5 showed a possible catalytic cycle of the Photo-Fenton reaction of Fe3O4@HG. The photo-generated electrons formed and transferred by rapid chain cycle reactions on the surface of HG under light, accelerated the conversion of Fe3 þ to Fe2 þ due to the good absorption and electrons conductivity of HG, and made the photocatalytic efficiency and rate of Fe3O4@HG improve.
[1] H.Y. Xu, T.N. Shi, H. Zhao, L.G. Jin, F.C. Wang, C.Y. Wang, et al., Front. Mater. Sci. 10 (2016) 45–55. [2] S. Wang, J. Wei, S.S. Lv, Z.Y. Guo, F. Jiang, Clean-Soil Air Water 41 (2013) 992–1001. [3] B.C. Qiu, Q.Y. Li, B. Shen, M.Y. Xing, J.L. Zhang, Appl. Catal. B: Environ. 18 (2016) 216–223. [4] Y.H. Chang, Y.F. Yao, H. Luo, L. Cui, L.J. Zhi, Int. J. Nanomanuf. 10 (2014) 132–141. [5] L.Q. Wang, P.J. Wang, Y. Liu, L.H. Zheng, Q. Sun, S.B. Qiu, et al., RSC Adv. 5 (2015) 38696–38705. [6] D.C. Marcano, D.V. Kosynkin, J.M. Berlin, A. Sinitskii, Z. Sun, A. Slesarev, et al., ACS Nano 4 (2010) 4806–4814. [7] M. Zong, Y. Huang, Y. Zhao, L. Wang, P.B. Liu, Y. Wang, et al., Mater. Lett. 106 (2013) 22–25.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Preparation and performance of Fe3O4@hydrophilic graphene composites with excellent Photo-Fenton activity for photocatalysis Pengjun Wang, Liqiu Wang n, Qi Sun, Shaobo Qiu, Yang Liu, Xiaobo Zhang, Xuelong Liu, Lihui Zheng College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao, 066004 China
art ic l e i nf o
a b s t r a c t
Article history: Received 19 April 2016 Received in revised form 15 July 2016 Accepted 16 July 2016 Available online 18 July 2016
Composites (Fe3O4@HG) of hydrophilic graphene (HG) and Fe3O4 from an iron precursor of FeC13 6H2O and (NH4)2Fe(SO4)2 6H2O were prepared without any organic surfactants by a facile chemical co-precipitation method. Fe3O4 nanoparticles in Fe3O4@HG were about 15 nm in dimension and were ultradispersed on HG nanosheets. Fe3O4@HG exhibited paramagnetic characteristic and better stability in water. Photo-Fenton reaction results demonstrated that Fe3O4@HG composites could degrade methylorange (MO) dye with high efficiency in a short time. When the loading capacity of HG in Fe3O4@HG composites was 53.81 wt%, the catalytic efficiency could reach 87.68% after 30 min and the catalytic rate could be 0.055 mg min 1 in the first five minutes. A possible catalytic cycle for Fe3O4@HG catalyzed photo degradation of the dye was elucidated. The photo-generated electrons were transferred rapidly on the surface of HG and promoted the conversion efficiency of Fe3 þ /Fe2 þ due to the good absorption and electronic conductivity of HG. The composites would be applied as photo-catalysts for treatment of wastewater. & 2016 Elsevier B.V. All rights reserved.
Keywords: Magnetic graphene composites Hydrophilic graphene and Fe3O4 Paramagnetic characteristic Photo degradation Photo-Fenton activity
1. Introduction Applications of organic dyes in industries lead to the discharge of an amount of colored wastewater and bring environmental contaminants [1]. Advanced oxidation processes based on Fenton's reaction are successful for degradation of the contaminated water. But they suffer from the disadvantages of difficult separation and recovery for the Fe2 þ metal ions, so magnetic Fenton-like catalysts are developed. Fe3O4 has good magnetic properties and is one of the most promising Fenton-like catalysts [2]. The coexistence of Fe2 þ and Fe3 þ in Fe3O4 octahedral structure [3,4] could improve the catalytic activity of Fenton reaction and enhance degradation efficiency for the dye contaminants. But Fe3O4 nanoparticles are prone to aggregate during the Fenton process, lose dispersion stability and diminish their catalytic activity. Graphene (Gr) could prevent the aggregation of Fe3O4 nanoparticles and increase the catalytic efficiency of Fenton reaction because of excellent specific area and electrical conductivity, so it has become an ideal support used for the anchor of Fe3O4 nanoparticles and the most promising building block for photocatalysis. But the problem is that it could not composite with Fe3O4 well due to its hydrophobicity. A novel type of hydrophilic graphene (HG), which not only n
Corresponding author. E-mail address: [email protected] (L. Wang).
http://dx.doi.org/10.1016/j.matlet.2016.07.080 0167-577X/& 2016 Elsevier B.V. All rights reserved.
remained the pristine structure of Gr, but also exhibited high dispersion property in aqueous solution, was developed in our previous work [5]. In this paper, novel magnetic Fe3O4@HG composites have been developed from the HG and Fe3O4. The composites have excellent dispersion stability in water and PhotoFenton reaction catalytic activity due to the presence of the synergetic effect between the Fe3O4 nanoparticles and HG, and are expected to be applied as effective catalysts for the removal of dyes in wastewater.
2. Materials and methods 2.1. Preparation of GO and HG Graphene oxide (GO) was synthesized by the improved Hummers' method [6], and HG was prepared by GO reacting with phenylhydrazine-4-sulfonic acid at 85 °C for 12 h [5]. 2.2. Preparation of Fe3O4@HG composites 6 mL mixed iron salt (MIS) from 24 mg FeC13 6H2O and 19.2 mg (NH4)2Fe(SO4)2 6H2O in water was treated under ultrasonic for 5 min. Different volumes of 6.00 mg mL 1 HG solution were added to the MIS, adjusting the total volume of reaction solution to 25 mL by deionized water. After 5 mL strong ammonia
62
P. Wang et al. / Materials Letters 183 (2016) 61–64
was added, the mixture was kept at 85 °C for 1 h under N2. Cooling the mixture naturally to room temperature, Fe3O4@HG nanoparticles were obtained by magnetic separation, washed several times with deionized water and dried at 60 °C under vacuum. As above, three types of Fe3O4@HG nanoparticles could be prepared by adding different volumes of HG solution: (a) 0.5 mL, (b) 2.0 mL and (c) 8.0 mL, and the corresponding mass fraction of HG was about 22.56 wt%, 53.81 wt% and 82.33 wt%, respectively. For comparison, Fe3O4 (d) was synthesized by the above method without HG. 2.3. Photo-Fenton reaction activity Activity of Photo-Fenton reaction of Fe3O4@HG was evaluated by the degradation of methyl-orange (MO) under 500 W high-voltage mercury lamp [3]. 3 mg of Fe3O4@HG was added into 50 mL 10 mg L 1 MO solution. After adjusting the pH value to 3.5 with 0.1 M H2SO4, the Fenton reaction was initiated by adding H2O2 (1.2 mL, 30 wt%). At the given time intervals, the analytic samples were taken from the mixture and analyzed by UV–vis spectra after they were centrifuged and filtrated by a 0.45 mm filter film. 2.4. Characterization Zetasizer Nano ZS from Malvern Instrument was used for the Zeta potential measurements. Fourier transform infrared (FT-IR) spectra were measured by using a Nicolet iS10 spectrometer. X-ray diffraction (XRD) patterns of samples were collected by using D-max-2500 XRD analysis meter with Cu Kα radiation (λ ¼0.154 nm). Transmission electron microscopic (TEM) images were obtained by using a Hitachi HT7700 transmission electron microscopy at an accelerating voltage of 100 kV. Scanning electron microscopic (SEM) images were acquired by a Hitachi S-4800 S2 field emission scanning electron microscopy. Thickness information of the samples was obtained by multimode 8 at. force microscopes (AFM). Magnetic properties of the samples were measured by vibrating sample magnetometer lake shore 7407 and the magnetic hysteresis loop was obtained by varying magnetic field between þ 20,000 and 20,000 Oe at 300 K.
3. Results and discussion Fe3O4@HG composites were characterized by TEM, AFM and SEM. As shown in Fig. 1(A) and (B), Fe3O4 nanoparticles with diameter of 15 nm in average were uniformly distributed on the surface of HG nanosheets. The inset in Fig. 1(B) revealed the
thickness of Fe3O4@HG composites was around 18 nm. Fig. 1 (C) exhibited Fe3O4 nanoparticles were assembled and grew upright with high density in the layers of HG nanosheets which effectively prevented the agglomeration of Fe3O4 nanoparticles. Fig. 2(A) showed the deformation vibration of S–O at 1178, 1125 cm 1 and S-phenyl at 1035 cm 1 attributing to the sulfonic groups of HG in Fe3O4@HG [2]. Compared to 591 cm 1 of the pristine Fe3O4, the peak at 574 cm 1 corresponding to the Fe-O stretching vibration became blue shift due to the interaction between Fe3O4 nanoparticle and HG nanosheets. Fig. 2(B) exhibited that the XRD patterns of Fe3O4@HG were similar to that of the pristine Fe3O4. The diffraction peaks at 2θ ¼30.24, 35.56, 43.24, 53.66, 57.20 and 62.82° were corresponding to the (220), (311), (400), (422), (511) and (440) reflections of standard Fe3O4 (JCPDS no.19-0629) [7]. Fig. 3(A) demonstrated that the absolute value of zeta potential (AVZP) of Fe3O4@HG composites was above 27 mv, which was greater than 19.53 mv of pristine Fe3O4. So Fe3O4@HG had better stability in water than pristine Fe3O4. Furthermore, when the loading capacity of HG was increased from 22.56 to 82.33 wt%, the AVZP of Fe3O4@HG was improved from 27.1 to 38.1 mv, and this illustrated that it was HG that promoted the dispersion of Fe3O4 nanoparticles in water. The dispersing image was also shown in the inset of Fig. 3(A). With increasing amount of HG, the dispersion of Fe3O4@HG became more stable. Fig. 3 (B) exhibited the S-like shape of magnetization curves without going through the origin point and all samples possessed paramagnetic behavior, so they could be separated easily and rapidly from their mixtures due to their fast magnetic response under an external magnetic field. When the loading capacity of HG was increased from 22.56 to 82.33 wt%, the specific saturation magnetizations of Fe3O4@HG were gradually decreased from 31.86 to 5.84 emu g 1 because the Fe3O4/HG ratio in Fe3O4@HG decreased with increasing HG, and this weakened the exhibition of magnetization of Fe3O4@HG. So the magnetic response might be controlled by the loading capacity of HG in Fe3O4@HG, and this made the separation speed of Fe3O4@HG become more flexible. In order to investigate the photocatalytic activity, Fe3O4@HG composites were applied to degrade MO by Photo-Fenton reaction. The catalytic efficiency (Ec) and catalytic rate (Rc) were calculated by the following equations:
E c( %) = A 0 −A t /A 0 × 100
(
)
R c mgmin−1 =Mc/t
(1) (2)
A0 and At were the absorbance at 465 nm of the MO samples at the initial time and different interval time t, respectively, and Mc
Fig. 1. (A) TEM and Fe3O4 size distribution, (B) AFM and its thickness and (C) SEM image of a Fe3O4@HG composite (sample b).
P. Wang et al. / Materials Letters 183 (2016) 61–64
63
Fig. 2. (A) FT-IR spectra and (B) XRD patterns.
Fig. 3. (A) Zeta potential and the dispersion image and (B) magnetization curves of the samples.
Fig. 4. (A) Catalytic efficiency and (B) Catalytic rate of the samples for degrading MO.
(mg) was the mass of MO photodegraded. Fig. 4(A) showed that Ec increased with the increasing time from 5 to 30 min. Pristine Fe3O4 had the weakest Ec (9.46%, 30 min), while samples (a), (b) and (c) demonstrated a high Ec due to the presence of HG. When the loading capacity of HG in Fe3O4@HG was 53.81 wt%, the maximum Ec could reach 87.68%. But when the content of HG increased to 82.33 wt%, the Ec decreased to 65.59%. Rc shown in Fig. 4(B) exhibited the same changing tendency with the
corresponding Ec, sample (d) had the slowest catalytic rate (0.00283 mg min 1, 5 min), and sample (b) demonstrated the largest Rc (0.055 mg min 1, 5 min). Overmuch HG in Fe3O4@HG led to the decrease of Ec and Rc, the reason might be that excess HG covered up Fe3O4 particles, made the exposed specific area of Fe3O4 particles in Fe3O4@HG reduce, and minimized the photocatalytic activity. As a result, the optimal loading capacity of HG in Fe3O4@HG for Photo-Fenton reaction activity was 53.81 wt%.
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P. Wang et al. / Materials Letters 183 (2016) 61–64
4. Conclusions Fe3O4@HG composites were synthesized by co-precipitating methods. The Fe3O4 nanoparticles in Fe3O4@HG with average size of 15 nm were uniformly and densely tethered onto HG nanosheets. The composites demonstrated paramagnetic characteristic, better stability in water, and higher Photo-Fenton activity. The Fe3O4@HG composites would provide a promising pathway in the removal of dyes in wastewater.
Acknowledgments The authors would like to thank Hebei Natural Science Foundation (No. B2015203259) and Yanshan University Graduate Course Construction (No. SF201412) for providing the financial support for this project. Fig. 5. The Photo-Fenton catalytic cycle of Fe3O4@HG.
References Pristine Fe3O4 exhibited the weakest Photo-Fenton reaction activity because of the deposition of Fe(OH)3 formed during the photocatalytic process, while Fe3O4@HG could limit the formation of Fe(OH)3 due to the rapid reduction of Fe3 þ into Fe2 þ . Fig. 5 showed a possible catalytic cycle of the Photo-Fenton reaction of Fe3O4@HG. The photo-generated electrons formed and transferred by rapid chain cycle reactions on the surface of HG under light, accelerated the conversion of Fe3 þ to Fe2 þ due to the good absorption and electrons conductivity of HG, and made the photocatalytic efficiency and rate of Fe3O4@HG improve.
[1] H.Y. Xu, T.N. Shi, H. Zhao, L.G. Jin, F.C. Wang, C.Y. Wang, et al., Front. Mater. Sci. 10 (2016) 45–55. [2] S. Wang, J. Wei, S.S. Lv, Z.Y. Guo, F. Jiang, Clean-Soil Air Water 41 (2013) 992–1001. [3] B.C. Qiu, Q.Y. Li, B. Shen, M.Y. Xing, J.L. Zhang, Appl. Catal. B: Environ. 18 (2016) 216–223. [4] Y.H. Chang, Y.F. Yao, H. Luo, L. Cui, L.J. Zhi, Int. J. Nanomanuf. 10 (2014) 132–141. [5] L.Q. Wang, P.J. Wang, Y. Liu, L.H. Zheng, Q. Sun, S.B. Qiu, et al., RSC Adv. 5 (2015) 38696–38705. [6] D.C. Marcano, D.V. Kosynkin, J.M. Berlin, A. Sinitskii, Z. Sun, A. Slesarev, et al., ACS Nano 4 (2010) 4806–4814. [7] M. Zong, Y. Huang, Y. Zhao, L. Wang, P.B. Liu, Y. Wang, et al., Mater. Lett. 106 (2013) 22–25.