- Email: [email protected]
A new efficient visible-light-driven composite photocatalyst comprising ZnFe2O4 nanoparticles and conjugated polymer from the dehydrochlorination of polyvinyl chloride
Materials Letters 187 (2017) 123–125
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
A new efficient visible-light-driven composite photocatalyst comprising ZnFe2O4 nanoparticles and conjugated polymer from the dehydrochlorination of polyvinyl chloride
crossmark
⁎
Bin Xua,c, Tao Dingb, Yongcai Zhanga, , Yaoting Wena, Zhanjun Yanga, Ming Zhanga a b c
School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, China Yongcheng Vocational College, Yongcheng 476600, China The Testing Center, Yangzhou University, Yangzhou 225009, China
A R T I C L E I N F O
A BS T RAC T
Keywords: Composite materials Nanocomposites Semiconductors Solar energy materials
This communication reports the development of a new efficient visible-light-driven composite photocatalyst comprising ZnFe2O4 nanoparticles and conjugated polymer (CPVC) from the dehydrochlorination of polyvinyl chloride (PVC). ZnFe2O4/CPVC nanocomposites were synthesized via three main steps: (i) the synthesis of ZnFe2O4 nanoparticles by a sol-gel method; (ii) the adsorption of PVC in tetrahydrofuran solution by ZnFe2O4 nanoparticles to form ZnFe2O4/PVC nanocomposites; and (iii) the dehydrochlorination of PVC in the ZnFe2O4/ PVC nanocomposites by heating at 150 °C for 2 h. X-ray diffraction, Fourier transform infrared spectroscopy and high-resolution transmission electron microscopy characterization revealed that the as-synthesized product was core/shell structured ZnFe2O4/CPVC nanocomposites. The photocatalytic results demonstrated that the ZnFe2O4/CPVC nanocomposites had much higher photocatalytic activity than ZnFe2O4 nanoparticles in the reduction of aqueous Cr(VI) under visible-light (λ > 420 nm) irradiation. Thus, ZnFe2O4/CPVC nanocomposites are promising for use as a new efficient visible-light-driven photocatalyst.
1. Introduction
(PVC) is a common cheap polymer that has been widely used in a great variety of fields. When PVC is heated at proper temperatures, it would release HCl, generating a new polymer with conjugated polyene sequence (CPVC) [11–14]. The long-chain conjugated polyene structure of CPVC endows it with semiconducting properties and good visible-light-absorbing ability [13,14]. Hence, CPVC is capable of modifying other semiconductors to create new high performance visible-light-driven photocatalysts [11–14]. It has been reported that the potentials of the valence band (VB) and conduction band (CB) of ZnFe2O4 were 0.38 V and −1.54 V vs NHE [4,5], whereas the potentials of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of CPVC (which was obtained by heating PVC at 150 °C for 2 h) were 0.46 V and −1.02 V vs NHE [11], respectively. Therefore, ZnFe2O4 and CPVC have matched electronic band structures, and they can form type-II heterojunction as shown in Scheme 1. When ZnFe2O4/CPVC nanocomposites were excited by light, the photogenerated electrons (e−) in the CB of ZnFe2O4 can transfer to the LUMO of CPVC, whereas the photogenerated holes (h+) in the HOMO of CPVC can transfer to the VB of ZnFe2O4. Thus, the separation of e− and h+ in ZnFe2O4/CPVC nanocomposites can be effectively enhanced, and more e− and h+ can
The development of new efficient visible-light-driven photocatalysts is crucial for actual application of photocatalytic technology in treatment of environmental pollutants, production of H2 and reduction of CO2 [1–3], etc. ZnFe2O4, a narrow bandgap semiconductor (Eg=1.92 eV [4,5]), can absorb visible-light and has photocatalytic activity under visible-light irradiation [4–7]. Moreover, it also has the merits of good photochemical stability, low cost and environmental benignity. Hence, ZnFe2O4 has the potential for use as a visible-lightdriven photocatalyst. Nevertheless, sole ZnFe2O4 has the drawback of high recombination rate of its photogenerated electrons and holes, thus low photocatalytic efficiency [4–7]. Therefore, it is needed to explore a modification method to effectively improve the photocatalytic efficiency of ZnFe2O4. The coupling with conjugated polymers has been proved to be an alternative effective way for improving the photocatalytic performance of semiconductor photocatalysts [8–10]. However, the conjugated polymers utilized hitherto to couple with semiconductor photocatalysts are usually polythiophene [8], polyaniline [9] and polypyrrole [10], which are difficult to synthesize and relatively costly. Polyvinyl chloride
⁎
Corresponding author. E-mail address: [email protected] (Y. Zhang).
http://dx.doi.org/10.1016/j.matlet.2016.10.094 Received 13 August 2016; Received in revised form 29 September 2016; Accepted 21 October 2016 Available online 24 October 2016 0167-577X/ © 2016 Elsevier B.V. All rights reserved.
Materials Letters 187 (2017) 123–125
(a)
Intensity (a. u.)
440
422 511
400
111
220
ZnFe2O4
222
311
B. Xu et al.
ZnFe2O4/CPVC CPVC
10
20
30
Scheme 1. The possible photogenerated charge transfer in ZnFe2O4/CPVC nanocomposites.
40 2θ (deg.)
50
60
(b)
ZnFe2O4
Transmittance
be used in the photocatalytic reactions. Accordingly, ZnFe2O4/CPVC nanocomposites would have higher photocatalytic efficiency than ZnFe2O4. Based on the above analysis, we attempted for the first time to use CPVC to modify ZnFe2O4, aiming to develop a new efficient visible-light-driven ZnFe2O4/CPVC composite photocatalyst. 2. Experimental ZnFe2O4/CPVC nanocomposites were synthesized via the following three steps. First, ZnFe2O4 nanoparticles were prepared according to the following procedures: 2.5 mmol Zn(NO3)2·6H2O, 5.0 mmol Fe(NO3)3·9H2O and 10 mmol citric acid were dissolved in 5.0 mL of deionized water, and the mixture was heated at 90 °C for 12 h to obtain a red gel; afterwards, the gel was calcined at 400 °C for 2 h to generate ZnFe2O4 nanoparticles. Second, 10 mg of PVC powder (K-value 72-71, Shanghai Aladdin Reagent Co., Ltd.) was dissolved in 25.0 mL of tetrahydrofuran, and 1000 mg of the as-prepared ZnFe2O4 nanoparticles was added to the PVC tetrahydrofuran solution. After the mixture was magnetically stirred for 2 h and ultrasonicated for 50 min, it was heated at 65 °C for 4 h to evaporate tetrahydrofuran, so ZnFe2O4/PVC nanocomposites were obtained. Third, ZnFe2O4/CPVC nanocomposites were produced by heating the ZnFe2O4/PVC nanocomposites in air at 150 °C for 2 h. The products were characterized using XRD (Bruker AXS D8 ADVANCE X-Ray Diffractometer), FTIR (Varian Cary 670 FT-IR spectrometer), and HRTEM (FEI Tecnai G2 F30 S-TWIN FieldEmission Transmission Electron Microscopy). Photocatalytic activities of the products were tested according to the procedures in our previous report [15].
ZnFe2O4/CPVC
70
C=C
4000 3500 3000 2500 2000 1500 1000 -1 Wavenumber (cm )
500
Fig. 1. (a) XRD spectra of the as-synthesized ZnFe2O4, ZnFe2O4/CPVC and CPVC; (b) FTIR spectra of the as-synthesized ZnFe2O4 and ZnFe2O4/CPVC.
Fig. 2(a) and (b) show the HRTEM images of ZnFe2O4 and ZnFe2O4/CPVC, respectively. It can be seen from Fig. 2(a) that ZnFe2O4 comprised nanoparticles with the size of about 9–21 nm. Moreover, some nanoparticles exhibited clear lattice fringes (d=0.46 nm) of the (111) crystal planes of spinel-type ZnFe2O4. On the other hand, the HRTEM image of ZnFe2O4/CPVC in Fig. 2(b) exhibited not only distinct lattice fringes of the (111) crystal planes of spinel-type ZnFe2O4, but also thin layer (about 2–3 nm) of amorphous CPVC on the surface of ZnFe2O4 nanocrystals. The as-synthesized ZnFe2O4/CPVC nanocomposites had a core/shell structure. Fig. 3 shows the dark adsorption and visible-light (λ > 420 nm)driven photocatalytic reduction of aqueous Cr(VI) by the as-synthesized ZnFe2O4/CPVC nanocomposites and ZnFe2O4 nanoparticles. It can be seen from Fig. 3 that the dark adsorption equilibrium of either product for Cr(VI) can be achieved after mixing for 40 min. The adsorption capacities of ZnFe2O4/CPVC nanocomposites and ZnFe2O4 nanoparticles for Cr(VI) were 10.2% and 6.5%, respectively. After the adsorption equilibrium, the concentration of Cr(VI) further decreased with exposure to visible-light (λ > 420 nm) irradiation, suggesting both products had visible-light-driven photocatalytic activity. However, the Cr(VI) concentration decreased much more quickly in the presence of ZnFe2O4/CPVC nanocomposites under visible-light irradiation, for example, when irradiated by visible-light for 240 min, the decrease of Cr(VI) concentration in the presence of ZnFe2O4/CPVC
3. Results and discussion Fig. 1(a) shows the XRD spectra of the as-synthesized ZnFe2O4, ZnFe2O4/CPVC and CPVC. As can be observed from Fig. 1(a), both the XRD spectra of the as-synthesized ZnFe2O4 and ZnFe2O4/CPVC exhibited the XRD peaks of spinel-type ZnFe2O4 (JCPDS Card No. 82–1042). No obvious XRD peaks of CPVC can be seen in the XRD spectrum of ZnFe2O4/CPVC. This was probably because the CPVC content in ZnFe2O4/CPVC was relatively small ( < 1 mass%) and CPVC was almost amorphous (Fig. 1(a)). However, the existence of CPVC in the as-synthesized ZnFe2O4/CPVC was confirmed by FTIR characterization. As can be seen from Fig. 1(b), besides the peaks displayed in the FTIR spectrum of ZnFe2O4, the FTIR spectrum of ZnFe2O4/CPVC also displayed an additional peak at about 1550 cm−1, which can be assigned to the stretching vibration of C=C bonds from CPVC [14]. 124
Materials Letters 187 (2017) 123–125
B. Xu et al.
Dark Irradiated ZnFe2O4 ZnFe2O4/CPVC
1.0
Ct/C0
0.8
0.6 Dark
Photocatalytic adsorption reactions
0.4 0
60
120 180 Time (min)
240
300
Fig. 3. Dark adsorption and visible-light (λ > 420 nm)-driven photocatalytic reduction of aqueous Cr(VI) by ZnFe2O4/CPVC nanocomposites and ZnFe2O4 nanoparticles. Note: C0 denotes the Cr(VI) concentration of the starting K2Cr2O7 aqueous solution (50 mg/L), and Ct denotes the Cr(VI) concentration of the K2Cr2O7 aqueous solution after dark adsorption and photocatalytic reduction for t min.
step method. Compared with ZnFe2O4 nanoparticles, ZnFe2O4/CPVC nanocomposites exhibited much improved photocatalytic efficiency in the reduction of aqueous Cr(VI) under visible-light (λ > 420 nm) irradiation. Hence, ZnFe2O4/CPVC nanocomposites had the potential for use as an efficient visible-light-driven photocatalyst in the treatment of Cr(VI)-polluted wastewater. Acknowledgments Thanks to the funds from National Natural Science Foundation of China (21475116), and The Priority Academic Program Development of Jiangsu Higher Education Institutions. References [1] [2] [3] [4] Fig. 2. HRTEM images of (a) ZnFe2O4 and (b) ZnFe2O4/CPVC.
[5]
nanocomposites and ZnFe2O4 nanoparticles were 55.8% (i.e., from 89.8–34.0%) and 23.2% (i.e., from 93.5–70.3%), respectively. This suggested that ZnFe2O4/CPVC nanocomposites had far higher visiblelight-driven photocatalytic activity than ZnFe2O4 nanoparticles.
[6] [7] [8] [9] [10] [11] [12] [13] [14] [15]
4. Conclusions A new efficient visible-light-driven photocatalyst was developed by coupling ZnFe2O4 nanoparticles with CPVC via our proposed three-
125
N. Sagara, S. Kamimura, T. Tsubota, T. Ohno, Appl. Catal. B 192 (2016) 193–198. K. Maeda, K. Domen, J. Catal. 310 (2014) 67–74. Y.C. Zhang, L. Yao, G. Zhang, D.D. Dionysiou, Appl. Catal. B 144 (2014) 730–738. S. Boumaza, A. Boudjemaa, A. Bouguelia, R. Bouarab, M. Trari, Appl. Energy 87 (2010) 2230–2236. S. Zhang, J. Li, M. Zeng, G. Zhao, X. Wang, ACS Appl. Mater. Interfaces 5 (2013) 12735–12743. X. Chen, Y. Dai, W. Huang, Mater. Lett. 145 (2015) 125–128. J. Feng, Y. Hou, X. Wang, L. Li, J. Alloy. Compd. 681 (2016) 157–166. T. Zheng, J. Xu, Z. Zhang, H. Zeng, Mater. Lett. 164 (2016) 640–643. S. Debnath, A. Maity, K. Pillay, Appl. Catal. B 163 (2015) 330–342. Q. Wang, L. Zheng, H. Huang, J. Alloy. Compd. 637 (2015) 127–132. D. Wang, H. Sun, Q. Luo, Appl. Catal. B 156–157 (2014) 323–330. D. Wang, C. Bao, Q. Luo, J. Environ. Chem. Eng. 3 (2015) 1578–1585. Y. Wen, S. Liu, Q. Zhang, Y. Zhang, Mater. Lett. 163 (2016) 262–265. Q. Luo, L. Wang, D. Wang, J. Environ. Chem. Eng. 3 (2015) 622–629. Y. Zhang, Q. Zhang, Sep. Purif. Technol. 142 (2015) 251–257.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
A new efficient visible-light-driven composite photocatalyst comprising ZnFe2O4 nanoparticles and conjugated polymer from the dehydrochlorination of polyvinyl chloride
crossmark
⁎
Bin Xua,c, Tao Dingb, Yongcai Zhanga, , Yaoting Wena, Zhanjun Yanga, Ming Zhanga a b c
School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, China Yongcheng Vocational College, Yongcheng 476600, China The Testing Center, Yangzhou University, Yangzhou 225009, China
A R T I C L E I N F O
A BS T RAC T
Keywords: Composite materials Nanocomposites Semiconductors Solar energy materials
This communication reports the development of a new efficient visible-light-driven composite photocatalyst comprising ZnFe2O4 nanoparticles and conjugated polymer (CPVC) from the dehydrochlorination of polyvinyl chloride (PVC). ZnFe2O4/CPVC nanocomposites were synthesized via three main steps: (i) the synthesis of ZnFe2O4 nanoparticles by a sol-gel method; (ii) the adsorption of PVC in tetrahydrofuran solution by ZnFe2O4 nanoparticles to form ZnFe2O4/PVC nanocomposites; and (iii) the dehydrochlorination of PVC in the ZnFe2O4/ PVC nanocomposites by heating at 150 °C for 2 h. X-ray diffraction, Fourier transform infrared spectroscopy and high-resolution transmission electron microscopy characterization revealed that the as-synthesized product was core/shell structured ZnFe2O4/CPVC nanocomposites. The photocatalytic results demonstrated that the ZnFe2O4/CPVC nanocomposites had much higher photocatalytic activity than ZnFe2O4 nanoparticles in the reduction of aqueous Cr(VI) under visible-light (λ > 420 nm) irradiation. Thus, ZnFe2O4/CPVC nanocomposites are promising for use as a new efficient visible-light-driven photocatalyst.
1. Introduction
(PVC) is a common cheap polymer that has been widely used in a great variety of fields. When PVC is heated at proper temperatures, it would release HCl, generating a new polymer with conjugated polyene sequence (CPVC) [11–14]. The long-chain conjugated polyene structure of CPVC endows it with semiconducting properties and good visible-light-absorbing ability [13,14]. Hence, CPVC is capable of modifying other semiconductors to create new high performance visible-light-driven photocatalysts [11–14]. It has been reported that the potentials of the valence band (VB) and conduction band (CB) of ZnFe2O4 were 0.38 V and −1.54 V vs NHE [4,5], whereas the potentials of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of CPVC (which was obtained by heating PVC at 150 °C for 2 h) were 0.46 V and −1.02 V vs NHE [11], respectively. Therefore, ZnFe2O4 and CPVC have matched electronic band structures, and they can form type-II heterojunction as shown in Scheme 1. When ZnFe2O4/CPVC nanocomposites were excited by light, the photogenerated electrons (e−) in the CB of ZnFe2O4 can transfer to the LUMO of CPVC, whereas the photogenerated holes (h+) in the HOMO of CPVC can transfer to the VB of ZnFe2O4. Thus, the separation of e− and h+ in ZnFe2O4/CPVC nanocomposites can be effectively enhanced, and more e− and h+ can
The development of new efficient visible-light-driven photocatalysts is crucial for actual application of photocatalytic technology in treatment of environmental pollutants, production of H2 and reduction of CO2 [1–3], etc. ZnFe2O4, a narrow bandgap semiconductor (Eg=1.92 eV [4,5]), can absorb visible-light and has photocatalytic activity under visible-light irradiation [4–7]. Moreover, it also has the merits of good photochemical stability, low cost and environmental benignity. Hence, ZnFe2O4 has the potential for use as a visible-lightdriven photocatalyst. Nevertheless, sole ZnFe2O4 has the drawback of high recombination rate of its photogenerated electrons and holes, thus low photocatalytic efficiency [4–7]. Therefore, it is needed to explore a modification method to effectively improve the photocatalytic efficiency of ZnFe2O4. The coupling with conjugated polymers has been proved to be an alternative effective way for improving the photocatalytic performance of semiconductor photocatalysts [8–10]. However, the conjugated polymers utilized hitherto to couple with semiconductor photocatalysts are usually polythiophene [8], polyaniline [9] and polypyrrole [10], which are difficult to synthesize and relatively costly. Polyvinyl chloride
⁎
Corresponding author. E-mail address: [email protected] (Y. Zhang).
http://dx.doi.org/10.1016/j.matlet.2016.10.094 Received 13 August 2016; Received in revised form 29 September 2016; Accepted 21 October 2016 Available online 24 October 2016 0167-577X/ © 2016 Elsevier B.V. All rights reserved.
Materials Letters 187 (2017) 123–125
(a)
Intensity (a. u.)
440
422 511
400
111
220
ZnFe2O4
222
311
B. Xu et al.
ZnFe2O4/CPVC CPVC
10
20
30
Scheme 1. The possible photogenerated charge transfer in ZnFe2O4/CPVC nanocomposites.
40 2θ (deg.)
50
60
(b)
ZnFe2O4
Transmittance
be used in the photocatalytic reactions. Accordingly, ZnFe2O4/CPVC nanocomposites would have higher photocatalytic efficiency than ZnFe2O4. Based on the above analysis, we attempted for the first time to use CPVC to modify ZnFe2O4, aiming to develop a new efficient visible-light-driven ZnFe2O4/CPVC composite photocatalyst. 2. Experimental ZnFe2O4/CPVC nanocomposites were synthesized via the following three steps. First, ZnFe2O4 nanoparticles were prepared according to the following procedures: 2.5 mmol Zn(NO3)2·6H2O, 5.0 mmol Fe(NO3)3·9H2O and 10 mmol citric acid were dissolved in 5.0 mL of deionized water, and the mixture was heated at 90 °C for 12 h to obtain a red gel; afterwards, the gel was calcined at 400 °C for 2 h to generate ZnFe2O4 nanoparticles. Second, 10 mg of PVC powder (K-value 72-71, Shanghai Aladdin Reagent Co., Ltd.) was dissolved in 25.0 mL of tetrahydrofuran, and 1000 mg of the as-prepared ZnFe2O4 nanoparticles was added to the PVC tetrahydrofuran solution. After the mixture was magnetically stirred for 2 h and ultrasonicated for 50 min, it was heated at 65 °C for 4 h to evaporate tetrahydrofuran, so ZnFe2O4/PVC nanocomposites were obtained. Third, ZnFe2O4/CPVC nanocomposites were produced by heating the ZnFe2O4/PVC nanocomposites in air at 150 °C for 2 h. The products were characterized using XRD (Bruker AXS D8 ADVANCE X-Ray Diffractometer), FTIR (Varian Cary 670 FT-IR spectrometer), and HRTEM (FEI Tecnai G2 F30 S-TWIN FieldEmission Transmission Electron Microscopy). Photocatalytic activities of the products were tested according to the procedures in our previous report [15].
ZnFe2O4/CPVC
70
C=C
4000 3500 3000 2500 2000 1500 1000 -1 Wavenumber (cm )
500
Fig. 1. (a) XRD spectra of the as-synthesized ZnFe2O4, ZnFe2O4/CPVC and CPVC; (b) FTIR spectra of the as-synthesized ZnFe2O4 and ZnFe2O4/CPVC.
Fig. 2(a) and (b) show the HRTEM images of ZnFe2O4 and ZnFe2O4/CPVC, respectively. It can be seen from Fig. 2(a) that ZnFe2O4 comprised nanoparticles with the size of about 9–21 nm. Moreover, some nanoparticles exhibited clear lattice fringes (d=0.46 nm) of the (111) crystal planes of spinel-type ZnFe2O4. On the other hand, the HRTEM image of ZnFe2O4/CPVC in Fig. 2(b) exhibited not only distinct lattice fringes of the (111) crystal planes of spinel-type ZnFe2O4, but also thin layer (about 2–3 nm) of amorphous CPVC on the surface of ZnFe2O4 nanocrystals. The as-synthesized ZnFe2O4/CPVC nanocomposites had a core/shell structure. Fig. 3 shows the dark adsorption and visible-light (λ > 420 nm)driven photocatalytic reduction of aqueous Cr(VI) by the as-synthesized ZnFe2O4/CPVC nanocomposites and ZnFe2O4 nanoparticles. It can be seen from Fig. 3 that the dark adsorption equilibrium of either product for Cr(VI) can be achieved after mixing for 40 min. The adsorption capacities of ZnFe2O4/CPVC nanocomposites and ZnFe2O4 nanoparticles for Cr(VI) were 10.2% and 6.5%, respectively. After the adsorption equilibrium, the concentration of Cr(VI) further decreased with exposure to visible-light (λ > 420 nm) irradiation, suggesting both products had visible-light-driven photocatalytic activity. However, the Cr(VI) concentration decreased much more quickly in the presence of ZnFe2O4/CPVC nanocomposites under visible-light irradiation, for example, when irradiated by visible-light for 240 min, the decrease of Cr(VI) concentration in the presence of ZnFe2O4/CPVC
3. Results and discussion Fig. 1(a) shows the XRD spectra of the as-synthesized ZnFe2O4, ZnFe2O4/CPVC and CPVC. As can be observed from Fig. 1(a), both the XRD spectra of the as-synthesized ZnFe2O4 and ZnFe2O4/CPVC exhibited the XRD peaks of spinel-type ZnFe2O4 (JCPDS Card No. 82–1042). No obvious XRD peaks of CPVC can be seen in the XRD spectrum of ZnFe2O4/CPVC. This was probably because the CPVC content in ZnFe2O4/CPVC was relatively small ( < 1 mass%) and CPVC was almost amorphous (Fig. 1(a)). However, the existence of CPVC in the as-synthesized ZnFe2O4/CPVC was confirmed by FTIR characterization. As can be seen from Fig. 1(b), besides the peaks displayed in the FTIR spectrum of ZnFe2O4, the FTIR spectrum of ZnFe2O4/CPVC also displayed an additional peak at about 1550 cm−1, which can be assigned to the stretching vibration of C=C bonds from CPVC [14]. 124
Materials Letters 187 (2017) 123–125
B. Xu et al.
Dark Irradiated ZnFe2O4 ZnFe2O4/CPVC
1.0
Ct/C0
0.8
0.6 Dark
Photocatalytic adsorption reactions
0.4 0
60
120 180 Time (min)
240
300
Fig. 3. Dark adsorption and visible-light (λ > 420 nm)-driven photocatalytic reduction of aqueous Cr(VI) by ZnFe2O4/CPVC nanocomposites and ZnFe2O4 nanoparticles. Note: C0 denotes the Cr(VI) concentration of the starting K2Cr2O7 aqueous solution (50 mg/L), and Ct denotes the Cr(VI) concentration of the K2Cr2O7 aqueous solution after dark adsorption and photocatalytic reduction for t min.
step method. Compared with ZnFe2O4 nanoparticles, ZnFe2O4/CPVC nanocomposites exhibited much improved photocatalytic efficiency in the reduction of aqueous Cr(VI) under visible-light (λ > 420 nm) irradiation. Hence, ZnFe2O4/CPVC nanocomposites had the potential for use as an efficient visible-light-driven photocatalyst in the treatment of Cr(VI)-polluted wastewater. Acknowledgments Thanks to the funds from National Natural Science Foundation of China (21475116), and The Priority Academic Program Development of Jiangsu Higher Education Institutions. References [1] [2] [3] [4] Fig. 2. HRTEM images of (a) ZnFe2O4 and (b) ZnFe2O4/CPVC.
[5]
nanocomposites and ZnFe2O4 nanoparticles were 55.8% (i.e., from 89.8–34.0%) and 23.2% (i.e., from 93.5–70.3%), respectively. This suggested that ZnFe2O4/CPVC nanocomposites had far higher visiblelight-driven photocatalytic activity than ZnFe2O4 nanoparticles.
[6] [7] [8] [9] [10] [11] [12] [13] [14] [15]
4. Conclusions A new efficient visible-light-driven photocatalyst was developed by coupling ZnFe2O4 nanoparticles with CPVC via our proposed three-
125
N. Sagara, S. Kamimura, T. Tsubota, T. Ohno, Appl. Catal. B 192 (2016) 193–198. K. Maeda, K. Domen, J. Catal. 310 (2014) 67–74. Y.C. Zhang, L. Yao, G. Zhang, D.D. Dionysiou, Appl. Catal. B 144 (2014) 730–738. S. Boumaza, A. Boudjemaa, A. Bouguelia, R. Bouarab, M. Trari, Appl. Energy 87 (2010) 2230–2236. S. Zhang, J. Li, M. Zeng, G. Zhao, X. Wang, ACS Appl. Mater. Interfaces 5 (2013) 12735–12743. X. Chen, Y. Dai, W. Huang, Mater. Lett. 145 (2015) 125–128. J. Feng, Y. Hou, X. Wang, L. Li, J. Alloy. Compd. 681 (2016) 157–166. T. Zheng, J. Xu, Z. Zhang, H. Zeng, Mater. Lett. 164 (2016) 640–643. S. Debnath, A. Maity, K. Pillay, Appl. Catal. B 163 (2015) 330–342. Q. Wang, L. Zheng, H. Huang, J. Alloy. Compd. 637 (2015) 127–132. D. Wang, H. Sun, Q. Luo, Appl. Catal. B 156–157 (2014) 323–330. D. Wang, C. Bao, Q. Luo, J. Environ. Chem. Eng. 3 (2015) 1578–1585. Y. Wen, S. Liu, Q. Zhang, Y. Zhang, Mater. Lett. 163 (2016) 262–265. Q. Luo, L. Wang, D. Wang, J. Environ. Chem. Eng. 3 (2015) 622–629. Y. Zhang, Q. Zhang, Sep. Purif. Technol. 142 (2015) 251–257.