- Email: [email protected]
bone char composites
Accepted Manuscript Enhanced photocatalytic performance of ZnO/bone char composites Puqi Jia, Hongwei Tan, Kuiren Liu, Wei Gao PII: DOI: Reference:
S0167-577X(17)31000-5 http://dx.doi.org/10.1016/j.matlet.2017.06.099 MLBLUE 22811
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
26 May 2017 19 June 2017 20 June 2017
Please cite this article as: P. Jia, H. Tan, K. Liu, W. Gao, Enhanced photocatalytic performance of ZnO/bone char composites, Materials Letters (2017), doi: http://dx.doi.org/10.1016/j.matlet.2017.06.099
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.
Enhanced photocatalytic performance of ZnO/bone char composites Puqi Jia†,‡, Hongwei Tan‡, Kuiren Liu†, Wei Gao*,‡ †
Department of Nonferrous Metallurgy, School of Metallurgy, Northeastern University, Shenyang 110819, China ‡
Department of Chemical and Materials Engineering, the University of Auckland, Auckland 1142, New Zealand *Email address: [email protected]
Abstract Novel composite photocatalysts ZnO/bone char (ZnO/BC) were prepared using a simple chemical precipitation method by integrating ZnO precursor with bone or pyrolytic bone char. UV–vis DRS showed that the increase of pyrolytic bone char in ZnO/BC composites enhanced the absorbance of visible light. The photocatalytic activities of ZnO/BC were examined by photocatalytic degradation of alkaline methylene blue dye under simulated sunlight irradiation. Result showed that with ZnO nano-particle precipitation on the surface of pyrolytic bone char, the ZnO/BC can fully utilize visible light to decompose methylene blue. This study indicates that the combination and treatment of ZnO/BC result in a very good photocatalytic performance; and this composite can be used for large scale wastewater treatment. Key words: ZnO, bone char, pyrolysis, sintering, FTIR, photocatalytic activity. 1. Introduction It has been demonstrated that ZnO is a better photocatalyst compared with TiO2 because it can absorb a larger fraction of UV spectrum (the corresponding threshold of ZnO is 425 nm) [1]. ZnO also has properties of high electron mobility, good thermal stability, nontoxicity and low cost [2]. When using ZnO powder as photocatalyst, recovery of particles is a problem which may cause potential health and 1
environmental hazards. Therefore supporting catalysts on rigid substrates such as glass, metal, plastic and ceramic materials have been studied as an important topic for ZnO applications. However a significant reduction in the system efficiency occurs because the substrates have no contributions to the photocatalytic process [3]. With large surface areas and low-cost, the mesoporous bone char (main component is hydroxyapatite, Ca5(PO4) 3(OH)), has been used as adsorbent for effective removal of 17-β oestradiol [4], endotoxin [5], Sr2+ [6], fluoride [7], and methylene blue [8, 9]. An early study demonstrated that a composite photocatalyst produced by calcination of the mixture of ZnO nanoparticles and bone char can has an improved properties of removing formaldehyde pollutants [10]. In this paper, we developed ZnO/BC composites by a simple chemical precipitation method. This method can give a homogeneous and firm ZnO monolayer on the surface of bone char. The objective of this study is to investigate the effect of preparation process of ZnO with waste bovine bone or bone char granules on the ZnO/BC catalysts' photocatalytic activity. The performance of ZnO/BC was evaluated by photocatalytic degradation of alkaline methylene blue (MB) dye under simulated sunlight irradiation. 2. Experimental Bone char was obtained by pyrolysis of bone granules with a size of 0.5–0.8 mm in a furnace at 400°C. ZnO precursor solution was prepared as reported before [11]. Zinc acetate dihydrate and capping agent (triethylamine, TEA) were mixed at a molar ratio of 1 : 1 in ethanol to obtain 0.2 M concentration. The mixed solution was stirred at 55°C for 1 h in a sealed container. The resulting cloudy solution indicated the growth of ZnO nanoparticles. ZnO was precipitated onto the surface of bone or bone char granules by a mass ratio of MZnO : Mcarrier = 1 : 11. The prepared samples were then dried at room temperature and sintered at 400°C. Table 1 listed the sample names and preparation methods. Group A represents adding 2
bone char into ZnO sol after pyrolysis of the bone granules. Group B made by adding bone granules into ZnO sol before pyrolysis. Table 1 The preparation methods of ZnO/BC samples. Sample
Supporting material
Pyrolysis time (h)
Sintering time (h)
A-ZnO/BC-1
bone char
1
1
A-ZnO/BC-2
bone char
2
1
B-ZnO/BC-1
bone
1
B-ZnO/BC-2
bone
2
X-ray diffractometer (Bruker, D2 Phaser) was used to identify the phases of ZnO/BC. Element ratios were determined by X-ray fluorescence spectrometer (PANalytical, MiniPal 2). The UV-visible absorption spectra (UV-vis DRS) were recorded on a UV-VIS spectrophotometer (Shimadzu, UV-2550) using BaSO4 as the reflectance standard. The Fourier-transform infrared spectra of samples were recorded on a FTIR spectrometer (PerkinElmer, Spectrum 100). The photodegradation capacity of ZnO/BC was performed with 4.48 mg/L of MB solution with initial pH of 10.4 because ZnO is not stable under extreme pH levels (≤5 or ≥11) [12]. The photocatalytic reaction system was cooled by a circulating water bath to maintain room temperature. Dark adsorption test was not carried out prior to the simulated sunlight illumination because of the fast adsorption of MB onto BC in the first 5 min contact. The photocatalytic experiments were conducted for 120 min under rich oxygen environment (air bubbled during the photodegradation process). The UVB (280–315 nm), UVA (315–400 nm) and Visible (380–780nm) radiations of the lamp were 2.2 W/m2, 5.1 W/m2 and 12 W/m2, respectively. MB concentration was evaluated by a UV-VIS Spectrometer (Perkin Elmer, Lambda 35) at 664 nm. The self-degradation rate of MB in blank experiment was about 15.5 %. 3. Results and discussion Fig. 1 shows the XRD patterns of the ZnO/BC samples. All detectable peaks can be indexed to the 3
hexagonal wurtzite structure of ZnO and hydroxyapatite. The samples A-ZnO/BC-2 and A-ZnO/BC-1 owned stronger peak intensities than the other two samples, indicating the increasing crystallinity and grain size.
Fig. 1 XRD patterns of ZnO/BC samples. The FTIR spectra in Fig. 2 show that the characteristic bands at 469, 563, 602, 961 and 1025 cm-1 came from PO43- ions, while the adsorption of atmospheric carbon dioxide on the ZnO/BC during the sample preparations followed the carbonate bands at ~872, 1416 and 1457 cm-1 [13, 14]. The band at 441 cm-1 was assigned to ZnO [15, 16]. On the other hand, the bands of Zn-O-P bond for ZnO/BC could not be observed, indicating that phosphorous predominantly existed in hydroxyapatite rather than a dopant interacting with ZnO crystal structure [17, 18].
Fig. 2 FTIR spectra of ZnO/BC samples.
Fig. 3 UV-Vis absorption spectra of BC and ZnO/BC samples. 4
The removal of organic matter in bone granules and removal of residual carbon in bone char during sintering process resulted in the actual ratios of ZnO to bone char to be 1 : 4.97 for B-ZnO/BC-1, 1 : 5.13 for B-ZnO/BC-2, 1 : 7.76 for A-ZnO/BC-1 and 1 : 11.99 for A-ZnO/BC-2. Fig. 3 shows that the increase of pyrolytic bone char in ZnO/BC composites enhanced the visible light absorbance between the wavelength of 400 and 800 nm. The intense adsorption in the UV region was produced by the transference of electron (e−) from the valence band to the conduction band of ZnO under high energy photon excitation [19]. The initial pH value (10.4) of MB solution was higher than the point of zero charge of ZnO/BC (pHPZC = 9.3). In this situation, the surface charge of ZnO/BC was negative [20]. Hence the methylene blue cation could be easily adsorbed on the ZnO/BC surface by electrostatic attractions. The nano-sized ZnO on ZnO/BC composites provided high specific surface area, and could adsorb a large amount of methylene blue dye as shown in Fig. 4. The larger ratios of ZnO particles of B-ZnO/BC-1 and B-ZnO/BC-2 than the other two samples resulted in higher adsorption efficiencies, indicating that ZnO particles have dispersed on the surface of bone char without aggregation. With the same initial pH value, the less adsorption left more free OH- in MB solution to generate more active •OH which could oxidize MB into inorganic molecules. The high visible light absorbance of A-ZnO/BC-2 has contributed to the photocatalytic degradation efficiency. Meanwhile, the high ZnO crystallinity may devote to the photocatalytic performance. Owing to these reasons, crystal A-ZnO/BC-2 has adequately utilized the visible light to excite a large amount of photoinduced holes (h+) to oxidize OH-, further effectively photodegradated methylene blue dye as shown in Fig. 4. The photocatalytic efficiency of B-ZnO/BC-2 was higher than B-ZnO/BC-1 due to the increased UVA absorbance.
5
Fig. 4 The removal efficiency of MB using ZnO/BC samples under dark or simulated sunlight illumination. 4. Conclusions ZnO/bone char composites have been successfully prepared using chemical precipitation method. The increase of pyrolytic bone char in ZnO/BC composites can enhance the visible light absorbance, significantly improving the photocatalytic activity of ZnO/BC composites. ZnO deposited on pyrolytic bone char followed by sintering treatment (A-ZnO/BC-2) has the best photocatalytic activity compared to the other three samples due to its high crystallinity and high level of visible light absorbance. This study indicates that ZnO/BC photocatalyst can efficiently utilize visible light to photodegradate alkaline methylene blue dye. Acknowledgements The authors would like to thank the funding supported by the China Scholarship Council, and the assistance from Advanced Materials Group and Department of Chemical & Materials Engineering, the University of Auckland. References [1] M.A. Behnajady, N. Modirshahla, R. Hamzavi, Kinetic study on photocatalytic degradation of C.I. Acid Yellow 23 by ZnO photocatalyst, J Hazard Mater 133(1-3) (2006) 226-32. [2] H. Zhang, F. Liu, Z. Mou, X. Liu, J. Sun, W. Lei, A facile one-step synthesis of ZnO quantum dots modified poly(triazine imide) nanosheets for enhanced hydrogen evolution under visible light, Chem 6
Commun (Camb) 52(88) (2016) 13020-13023. [3] K. Kabra, R. Chaudhary, R.L. Sawhney, Treatment of hazardous organic and inorganic compounds through aqueous-phase photocatalysis: a review, Ind. Eng. Chem. Res. 43(24) (2004) 7683-7696. [4] S. Patel, J. Han, W. Qiu, W. Gao, Synthesis and characterisation of mesoporous bone char obtained by pyrolysis of animal bones, for environmental application, J. Environ. Chem. Eng. 3(4) (2015) 2368-2377. [5] A. Rezaee, G. Ghanizadeh, G. Behzadiyannejad, A. Yazdanbakhsh, S. Siyadat, Adsorption of endotoxin from aqueous solution using bone char, Bull. Environ. Contam. Toxicol. 82(6) (2009) 732-737. [6] I. Smiciklas, S. Dimovic, M. Sljivic, I. Plecas, The batch study of Sr(2+) sorption by bone char, J Environ Sci Health A Tox Hazard Subst Environ Eng 43(2) (2008) 210-7. [7] N.A. Medellin-Castillo, R. Leyva-Ramos, R. Ocampo-Perez, R.F. Garcia de la Cruz, A. Aragon-Pina, J.M. Martinez-Rosales, R.M. Guerrero-Coronado, L. Fuentes-Rubio, Adsorption of fluoride from water solution on bone char, Ind. Eng. Chem. Res. 46(26) (2007) 9205-9212. [8] G. Ghanizadeh, G. Asgari, Adsorption kinetics and isotherm of methylene blue and its removal from aqueous solution using bone charcoal, React. Kinet., Mech. Catal. 102(1) (2011) 127-142. [9] U. Iriarte-Velasco, I. Sierra, E.A. Cepeda, R. Bravo, J.L. Ayastuy, Methylene blue adsorption by chemically activated waste pork bones, Color. Technol. 131(4) (2015) 322-332. [10] A. Rezaee, H. Rangkooy, A. Khavanin, A.J. Jafari, High photocatalytic decomposition of the air pollutant formaldehyde using nano-ZnO on bone char, Environ. Chem. Lett. 12(2) (2014) 353-357. [11] M. El-Kemary, H. El-Shamy, I. El-Mehasseb, Photocatalytic degradation of ciprofloxacin drug in water using ZnO nanoparticles, J. Lumin. 130(12) (2010) 2327-2331. [12] J. Han, W. Qiu, W. Gao, Potential dissolution and photo-dissolution of ZnO thin films, J Hazard Mater 178(1-3) (2010) 115-22. 7
[13] W. Wei, L. Yang, W. Zhong, S. Li, J. Cui, Z. Wei, Fast removal of methylene blue from aqueous solution by adsorption onto poorly crystalline hydroxyapatite nanoparticles, Digest J. Nanomat. Biostruct 19 (2015) 1343-1363. [14] D. Smolen, T. Chudoba, I. Malka, A. Kedzierska, W. Lojkowski, W. Swieszkowski, K.J. Kurzydlowski, M. Kolodziejczyk-Mierzynska, M. Lewandowska-Szumiel, Highly biocompatible, nanocrystalline hydroxyapatite synthesized in a solvothermal process driven by high energy density microwave radiation, Int J Nanomedicine 8 (2013) 653-68. [15] Z. Sun, Y. Deng, W. Zhang, Structure and property investigation of composite ZnO/SnO2 nanocrystalline particles after high-pressure treatment, Journal of Nanomaterials 2008 (2008) 1-5. [16] K. Segala, R.L. Dutra, C.V. Franco, A.S. Pereira, T. Trindadeb, In situ and ex situ preparations of ZnO/poly-{trans-[RuCl2 (vpy) 4]/styrene} nanocomposites, J. Braz. Chem. Soc. 21(10) (2010) 1986-1991. [17] O. Pawlig, R. Trettin, In-situ DRIFT spectroscopic investigation on the chemical evolution of zinc phosphate acid− base cement, Chem. Mater. 12(5) (2000) 1279-1287. [18] D.L. Sun, J.R. Deng, Z.S. Chao, Catalysis over zinc-incorporated berlinite (ZnAlPO4) of the methoxycarbonylation
of
1,6-hexanediamine
with
dimethyl
carbonate
to
form
dimethylhexane-1,6-dicarbamate, Chem Cent J 1 (2007) 27. [19] S. Sakthivel, B. Neppolian, M. Shankar, B. Arabindoo, M. Palanichamy, V. Murugesan, Solar photocatalytic degradation of azo dye: comparison of photocatalytic efficiency of ZnO and TiO 2, Sol. Energy Mater. Sol. Cells 77(1) (2003) 65-82. [20] S. Kanungo, K. Parida, Interfacial behavior of some synthetic MnO2 samples during their adsorption of Cu2+ and Ba2+ from aqueous solution at 300 K, J. Colloid Interface Sci. 98(1) (1984) 252-260. Figure Captions 8
Fig. 1 XRD patterns of ZnO/BC samples. Fig. 2 FTIR spectra of ZnO/BC samples. Fig. 3 UV-Vis adsorption spectra of BC and ZnO/BC samples. Fig. 4 The removal efficiency of MB using ZnO/BC samples under dark or simulated sunlight illumination.
9
• ZnO/bone char composites were prepared by a simple chemical precipitation method. • ZnO precursor was precipitated onto the surface of bone or pyrolytic bone char. • The increase of pyrolytic BC in ZnO/BC enhanced the visible light absorbance. • ZnO/BC can fully utilize visible light to decompose methylene blue dye.
10
11
S0167-577X(17)31000-5 http://dx.doi.org/10.1016/j.matlet.2017.06.099 MLBLUE 22811
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
26 May 2017 19 June 2017 20 June 2017
Please cite this article as: P. Jia, H. Tan, K. Liu, W. Gao, Enhanced photocatalytic performance of ZnO/bone char composites, Materials Letters (2017), doi: http://dx.doi.org/10.1016/j.matlet.2017.06.099
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.
Enhanced photocatalytic performance of ZnO/bone char composites Puqi Jia†,‡, Hongwei Tan‡, Kuiren Liu†, Wei Gao*,‡ †
Department of Nonferrous Metallurgy, School of Metallurgy, Northeastern University, Shenyang 110819, China ‡
Department of Chemical and Materials Engineering, the University of Auckland, Auckland 1142, New Zealand *Email address: [email protected]
Abstract Novel composite photocatalysts ZnO/bone char (ZnO/BC) were prepared using a simple chemical precipitation method by integrating ZnO precursor with bone or pyrolytic bone char. UV–vis DRS showed that the increase of pyrolytic bone char in ZnO/BC composites enhanced the absorbance of visible light. The photocatalytic activities of ZnO/BC were examined by photocatalytic degradation of alkaline methylene blue dye under simulated sunlight irradiation. Result showed that with ZnO nano-particle precipitation on the surface of pyrolytic bone char, the ZnO/BC can fully utilize visible light to decompose methylene blue. This study indicates that the combination and treatment of ZnO/BC result in a very good photocatalytic performance; and this composite can be used for large scale wastewater treatment. Key words: ZnO, bone char, pyrolysis, sintering, FTIR, photocatalytic activity. 1. Introduction It has been demonstrated that ZnO is a better photocatalyst compared with TiO2 because it can absorb a larger fraction of UV spectrum (the corresponding threshold of ZnO is 425 nm) [1]. ZnO also has properties of high electron mobility, good thermal stability, nontoxicity and low cost [2]. When using ZnO powder as photocatalyst, recovery of particles is a problem which may cause potential health and 1
environmental hazards. Therefore supporting catalysts on rigid substrates such as glass, metal, plastic and ceramic materials have been studied as an important topic for ZnO applications. However a significant reduction in the system efficiency occurs because the substrates have no contributions to the photocatalytic process [3]. With large surface areas and low-cost, the mesoporous bone char (main component is hydroxyapatite, Ca5(PO4) 3(OH)), has been used as adsorbent for effective removal of 17-β oestradiol [4], endotoxin [5], Sr2+ [6], fluoride [7], and methylene blue [8, 9]. An early study demonstrated that a composite photocatalyst produced by calcination of the mixture of ZnO nanoparticles and bone char can has an improved properties of removing formaldehyde pollutants [10]. In this paper, we developed ZnO/BC composites by a simple chemical precipitation method. This method can give a homogeneous and firm ZnO monolayer on the surface of bone char. The objective of this study is to investigate the effect of preparation process of ZnO with waste bovine bone or bone char granules on the ZnO/BC catalysts' photocatalytic activity. The performance of ZnO/BC was evaluated by photocatalytic degradation of alkaline methylene blue (MB) dye under simulated sunlight irradiation. 2. Experimental Bone char was obtained by pyrolysis of bone granules with a size of 0.5–0.8 mm in a furnace at 400°C. ZnO precursor solution was prepared as reported before [11]. Zinc acetate dihydrate and capping agent (triethylamine, TEA) were mixed at a molar ratio of 1 : 1 in ethanol to obtain 0.2 M concentration. The mixed solution was stirred at 55°C for 1 h in a sealed container. The resulting cloudy solution indicated the growth of ZnO nanoparticles. ZnO was precipitated onto the surface of bone or bone char granules by a mass ratio of MZnO : Mcarrier = 1 : 11. The prepared samples were then dried at room temperature and sintered at 400°C. Table 1 listed the sample names and preparation methods. Group A represents adding 2
bone char into ZnO sol after pyrolysis of the bone granules. Group B made by adding bone granules into ZnO sol before pyrolysis. Table 1 The preparation methods of ZnO/BC samples. Sample
Supporting material
Pyrolysis time (h)
Sintering time (h)
A-ZnO/BC-1
bone char
1
1
A-ZnO/BC-2
bone char
2
1
B-ZnO/BC-1
bone
1
B-ZnO/BC-2
bone
2
X-ray diffractometer (Bruker, D2 Phaser) was used to identify the phases of ZnO/BC. Element ratios were determined by X-ray fluorescence spectrometer (PANalytical, MiniPal 2). The UV-visible absorption spectra (UV-vis DRS) were recorded on a UV-VIS spectrophotometer (Shimadzu, UV-2550) using BaSO4 as the reflectance standard. The Fourier-transform infrared spectra of samples were recorded on a FTIR spectrometer (PerkinElmer, Spectrum 100). The photodegradation capacity of ZnO/BC was performed with 4.48 mg/L of MB solution with initial pH of 10.4 because ZnO is not stable under extreme pH levels (≤5 or ≥11) [12]. The photocatalytic reaction system was cooled by a circulating water bath to maintain room temperature. Dark adsorption test was not carried out prior to the simulated sunlight illumination because of the fast adsorption of MB onto BC in the first 5 min contact. The photocatalytic experiments were conducted for 120 min under rich oxygen environment (air bubbled during the photodegradation process). The UVB (280–315 nm), UVA (315–400 nm) and Visible (380–780nm) radiations of the lamp were 2.2 W/m2, 5.1 W/m2 and 12 W/m2, respectively. MB concentration was evaluated by a UV-VIS Spectrometer (Perkin Elmer, Lambda 35) at 664 nm. The self-degradation rate of MB in blank experiment was about 15.5 %. 3. Results and discussion Fig. 1 shows the XRD patterns of the ZnO/BC samples. All detectable peaks can be indexed to the 3
hexagonal wurtzite structure of ZnO and hydroxyapatite. The samples A-ZnO/BC-2 and A-ZnO/BC-1 owned stronger peak intensities than the other two samples, indicating the increasing crystallinity and grain size.
Fig. 1 XRD patterns of ZnO/BC samples. The FTIR spectra in Fig. 2 show that the characteristic bands at 469, 563, 602, 961 and 1025 cm-1 came from PO43- ions, while the adsorption of atmospheric carbon dioxide on the ZnO/BC during the sample preparations followed the carbonate bands at ~872, 1416 and 1457 cm-1 [13, 14]. The band at 441 cm-1 was assigned to ZnO [15, 16]. On the other hand, the bands of Zn-O-P bond for ZnO/BC could not be observed, indicating that phosphorous predominantly existed in hydroxyapatite rather than a dopant interacting with ZnO crystal structure [17, 18].
Fig. 2 FTIR spectra of ZnO/BC samples.
Fig. 3 UV-Vis absorption spectra of BC and ZnO/BC samples. 4
The removal of organic matter in bone granules and removal of residual carbon in bone char during sintering process resulted in the actual ratios of ZnO to bone char to be 1 : 4.97 for B-ZnO/BC-1, 1 : 5.13 for B-ZnO/BC-2, 1 : 7.76 for A-ZnO/BC-1 and 1 : 11.99 for A-ZnO/BC-2. Fig. 3 shows that the increase of pyrolytic bone char in ZnO/BC composites enhanced the visible light absorbance between the wavelength of 400 and 800 nm. The intense adsorption in the UV region was produced by the transference of electron (e−) from the valence band to the conduction band of ZnO under high energy photon excitation [19]. The initial pH value (10.4) of MB solution was higher than the point of zero charge of ZnO/BC (pHPZC = 9.3). In this situation, the surface charge of ZnO/BC was negative [20]. Hence the methylene blue cation could be easily adsorbed on the ZnO/BC surface by electrostatic attractions. The nano-sized ZnO on ZnO/BC composites provided high specific surface area, and could adsorb a large amount of methylene blue dye as shown in Fig. 4. The larger ratios of ZnO particles of B-ZnO/BC-1 and B-ZnO/BC-2 than the other two samples resulted in higher adsorption efficiencies, indicating that ZnO particles have dispersed on the surface of bone char without aggregation. With the same initial pH value, the less adsorption left more free OH- in MB solution to generate more active •OH which could oxidize MB into inorganic molecules. The high visible light absorbance of A-ZnO/BC-2 has contributed to the photocatalytic degradation efficiency. Meanwhile, the high ZnO crystallinity may devote to the photocatalytic performance. Owing to these reasons, crystal A-ZnO/BC-2 has adequately utilized the visible light to excite a large amount of photoinduced holes (h+) to oxidize OH-, further effectively photodegradated methylene blue dye as shown in Fig. 4. The photocatalytic efficiency of B-ZnO/BC-2 was higher than B-ZnO/BC-1 due to the increased UVA absorbance.
5
Fig. 4 The removal efficiency of MB using ZnO/BC samples under dark or simulated sunlight illumination. 4. Conclusions ZnO/bone char composites have been successfully prepared using chemical precipitation method. The increase of pyrolytic bone char in ZnO/BC composites can enhance the visible light absorbance, significantly improving the photocatalytic activity of ZnO/BC composites. ZnO deposited on pyrolytic bone char followed by sintering treatment (A-ZnO/BC-2) has the best photocatalytic activity compared to the other three samples due to its high crystallinity and high level of visible light absorbance. This study indicates that ZnO/BC photocatalyst can efficiently utilize visible light to photodegradate alkaline methylene blue dye. Acknowledgements The authors would like to thank the funding supported by the China Scholarship Council, and the assistance from Advanced Materials Group and Department of Chemical & Materials Engineering, the University of Auckland. References [1] M.A. Behnajady, N. Modirshahla, R. Hamzavi, Kinetic study on photocatalytic degradation of C.I. Acid Yellow 23 by ZnO photocatalyst, J Hazard Mater 133(1-3) (2006) 226-32. [2] H. Zhang, F. Liu, Z. Mou, X. Liu, J. Sun, W. Lei, A facile one-step synthesis of ZnO quantum dots modified poly(triazine imide) nanosheets for enhanced hydrogen evolution under visible light, Chem 6
Commun (Camb) 52(88) (2016) 13020-13023. [3] K. Kabra, R. Chaudhary, R.L. Sawhney, Treatment of hazardous organic and inorganic compounds through aqueous-phase photocatalysis: a review, Ind. Eng. Chem. Res. 43(24) (2004) 7683-7696. [4] S. Patel, J. Han, W. Qiu, W. Gao, Synthesis and characterisation of mesoporous bone char obtained by pyrolysis of animal bones, for environmental application, J. Environ. Chem. Eng. 3(4) (2015) 2368-2377. [5] A. Rezaee, G. Ghanizadeh, G. Behzadiyannejad, A. Yazdanbakhsh, S. Siyadat, Adsorption of endotoxin from aqueous solution using bone char, Bull. Environ. Contam. Toxicol. 82(6) (2009) 732-737. [6] I. Smiciklas, S. Dimovic, M. Sljivic, I. Plecas, The batch study of Sr(2+) sorption by bone char, J Environ Sci Health A Tox Hazard Subst Environ Eng 43(2) (2008) 210-7. [7] N.A. Medellin-Castillo, R. Leyva-Ramos, R. Ocampo-Perez, R.F. Garcia de la Cruz, A. Aragon-Pina, J.M. Martinez-Rosales, R.M. Guerrero-Coronado, L. Fuentes-Rubio, Adsorption of fluoride from water solution on bone char, Ind. Eng. Chem. Res. 46(26) (2007) 9205-9212. [8] G. Ghanizadeh, G. Asgari, Adsorption kinetics and isotherm of methylene blue and its removal from aqueous solution using bone charcoal, React. Kinet., Mech. Catal. 102(1) (2011) 127-142. [9] U. Iriarte-Velasco, I. Sierra, E.A. Cepeda, R. Bravo, J.L. Ayastuy, Methylene blue adsorption by chemically activated waste pork bones, Color. Technol. 131(4) (2015) 322-332. [10] A. Rezaee, H. Rangkooy, A. Khavanin, A.J. Jafari, High photocatalytic decomposition of the air pollutant formaldehyde using nano-ZnO on bone char, Environ. Chem. Lett. 12(2) (2014) 353-357. [11] M. El-Kemary, H. El-Shamy, I. El-Mehasseb, Photocatalytic degradation of ciprofloxacin drug in water using ZnO nanoparticles, J. Lumin. 130(12) (2010) 2327-2331. [12] J. Han, W. Qiu, W. Gao, Potential dissolution and photo-dissolution of ZnO thin films, J Hazard Mater 178(1-3) (2010) 115-22. 7
[13] W. Wei, L. Yang, W. Zhong, S. Li, J. Cui, Z. Wei, Fast removal of methylene blue from aqueous solution by adsorption onto poorly crystalline hydroxyapatite nanoparticles, Digest J. Nanomat. Biostruct 19 (2015) 1343-1363. [14] D. Smolen, T. Chudoba, I. Malka, A. Kedzierska, W. Lojkowski, W. Swieszkowski, K.J. Kurzydlowski, M. Kolodziejczyk-Mierzynska, M. Lewandowska-Szumiel, Highly biocompatible, nanocrystalline hydroxyapatite synthesized in a solvothermal process driven by high energy density microwave radiation, Int J Nanomedicine 8 (2013) 653-68. [15] Z. Sun, Y. Deng, W. Zhang, Structure and property investigation of composite ZnO/SnO2 nanocrystalline particles after high-pressure treatment, Journal of Nanomaterials 2008 (2008) 1-5. [16] K. Segala, R.L. Dutra, C.V. Franco, A.S. Pereira, T. Trindadeb, In situ and ex situ preparations of ZnO/poly-{trans-[RuCl2 (vpy) 4]/styrene} nanocomposites, J. Braz. Chem. Soc. 21(10) (2010) 1986-1991. [17] O. Pawlig, R. Trettin, In-situ DRIFT spectroscopic investigation on the chemical evolution of zinc phosphate acid− base cement, Chem. Mater. 12(5) (2000) 1279-1287. [18] D.L. Sun, J.R. Deng, Z.S. Chao, Catalysis over zinc-incorporated berlinite (ZnAlPO4) of the methoxycarbonylation
of
1,6-hexanediamine
with
dimethyl
carbonate
to
form
dimethylhexane-1,6-dicarbamate, Chem Cent J 1 (2007) 27. [19] S. Sakthivel, B. Neppolian, M. Shankar, B. Arabindoo, M. Palanichamy, V. Murugesan, Solar photocatalytic degradation of azo dye: comparison of photocatalytic efficiency of ZnO and TiO 2, Sol. Energy Mater. Sol. Cells 77(1) (2003) 65-82. [20] S. Kanungo, K. Parida, Interfacial behavior of some synthetic MnO2 samples during their adsorption of Cu2+ and Ba2+ from aqueous solution at 300 K, J. Colloid Interface Sci. 98(1) (1984) 252-260. Figure Captions 8
Fig. 1 XRD patterns of ZnO/BC samples. Fig. 2 FTIR spectra of ZnO/BC samples. Fig. 3 UV-Vis adsorption spectra of BC and ZnO/BC samples. Fig. 4 The removal efficiency of MB using ZnO/BC samples under dark or simulated sunlight illumination.
9
• ZnO/bone char composites were prepared by a simple chemical precipitation method. • ZnO precursor was precipitated onto the surface of bone or pyrolytic bone char. • The increase of pyrolytic BC in ZnO/BC enhanced the visible light absorbance. • ZnO/BC can fully utilize visible light to decompose methylene blue dye.
10
11