- Email: [email protected]
Preparation of porous carbon directly from hydrothermal carbonization of fructose and phloroglucinol for adsorption of tetracycline
Accepted Manuscript Title: Preparation of porous carbon directly from hydrothermal carbonization of fructose and phloroglucinol for adsorption of tetracycline Author: Chen-Xi Bai Feng Shen Xin-Hua Qi PII: DOI: Reference:
S1001-8417(17)30005-0 http://dx.doi.org/doi:10.1016/j.cclet.2016.12.026 CCLET 3932
To appear in:
Chinese Chemical Letters
Received date: Revised date: Accepted date:
3-11-2016 6-12-2016 12-12-2016
Please cite this article as: Chen-Xi Bai, Feng Shen, Xin-Hua Qi, Preparation of porous carbon directly from hydrothermal carbonization of fructose and phloroglucinol for adsorption of tetracycline, Chinese Chemical Letters http://dx.doi.org/10.1016/j.cclet.2016.12.026 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.
Original article Preparation of porous carbon directly from hydrothermal carbonization of fructose and phloroglucinol for adsorption of tetracycline Chen-Xi Bai a,b, Feng Shen b, Xin-Hua Qi b, * a b
College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China Agro-Environmental Protection Institute, Chinese Academy of Agricultural Sciences, Tianjin 300191, China
Corresponding author E-mail address: [email protected]
Article info
Article history Received 3 November 2016 Received in revised form 6 December 2016 Accepted 12 December 2016 Available online
Graphical Abstract
Porous carbonaceous material with large surface area (481.7 m2/g) and pore volume (0.73 cm3/g) was prepared directly from hydrothermal carbonization of fructose and phloroglucinol in hydroalcoholic mixture, which provides a green and efficient method to fabricate porous carbonaceous adsorbent that has great potential applications in chemical and environmental fields Abstract
Hydrothermal carbonization of biomass is a promising method to prepare carbonaceous materials. Generally, post physical or chemical activation is necessary to increase surface area and porosity of the carbon. Herein, porous carbonaceous material (FPC) with large surface area (481.7 m2/g) and pore volume (0.73 cm3/g) was prepared directly from hydrothermal carbonization of fructose and phloroglucinol in hydroalcoholic mixture. Structure characteristics of the FPC and its adsorption capacity for a representative antibiotic tetracycline in aqueous solution were investigated. This work provides a green and efficient method to fabricate porous carbonaceous adsorbent that has great potential applications in chemical and environmental fields. Keywords: Fructose Carbon materials Porous materials Adsorption Hydrothermal carbonization
1. Introduction Activated carbon is one of the most commonly used adsorbents due to its easy manipulation and high adsorption capacity. Generally, activated carbons are prepared by pyrolysis and activation of organic compounds. The activation process is normally divided into physical and chemical methods. Both the post-physical and chemical activation can generate carbons with pores and large specific surface area. However, these methods (pyrolysis and activation) have many disadvantages such as high energy consumption, low carbon yield, and large quantities of waste gas emission. Hydrothermal carbonization is a promising route to prepare carbon materials, providing low-cost, low temperature, and environmental friendly production from natural precursors in aqueous solution without the use of toxic reagents [1, 2]. The hydrothermal process involves heat treatment of carbohydrates solution under autogeneous pressure at relatively low temperatures (150-250 °C). The obtained solid carbon has uniform morphology and high content of oxygen-containing groups [3]. So far, carbonaceous materials from hydrothermal carbonization have been widely used in catalysis, adsorption and energy storage [4]. However, the carbon materials derived directly from hydrothermal carbonization of carbohydrates have only limited surface area and almost no porosity [5], greatly affecting the applications of the carbon materials. Thus, after the hydrothermal process, additional post treatment by pyrolysis or activation step at high temperature (>700 °C) are normally essential to introduce porosity within the carbon structure [6, 7]. In this work, porous carbon was synthesized directly from fructose and phloroglucinol in hydroalcoholic mixture via hydrothermal method without any post-treatment. Phloroglucinol herein acted as a cross-linking agent to greatly improve the porosity of the carbon material, which avoid additional post physical or chemical activation process. Fructose is a biomass-derived sugar, and phloroglucinol is the monomeric unit of phlorotannins and can be isolated from the bark of fruit trees [8] or brown algae [9]. The prepared highly porous carbonaceous adsorbents were employed for the adsorption of a representative antibiotics tetracycline in aqueous solution (chemical structure of tetracycline is shown in Fig. S1 in Supporting information), and exhibited excellent performances. 2. Results and discussion. It has been known that the hydrothermal carbonization of pure sugars (glucose, fructose, xylose, etc.) contains two steps: sugars are initially converted into HMF or furfural through intramolecular dehydration reaction, and then the furan compounds are condensed and polymerized to form carbonaceous materials [10]. However, the yield of carbons as well as the surface area is low from the pure sugars, which has limited its application, especially as an adsorbent. To solve this problem, phloroglucinol was employed herein as a co-polymer of fructose during hydrothermal carbonization. It can be seen that the product yield of FPC was 86%, which was 2.6-fold of FC (33%) (Table 1). Based on the N2 adsorption/desorption isotherms of FPC and FC (Fig. S2 in Supporting information), the surface area of FC obtained from hydrothermal treatment of sole fructose was calculated to be 75.4 m2/g. After the addition of phloroglucinol as the co-monomer of fructose in the same system, the BET surface area of the obtained carbonaceous material (FPC) was greatly increased to 481.7 m2/g. The total pore volume of FPC (0.73 cm3/g) was also much higher than that of FC (0.07 cm3/g), indicating that FPC had more abundant pore structure than FC, which was verified from the pore size distribution (Fig. S3 in Supporting information). The surface area and pore volume of FPC herein obtained directly from the hydrothermal carbonization of fructose and phloroglucinol were comparable to that of activated carbons generated by pyrolysis at 600- 800 °C [11]. The above results indicate that the addition of phloroglucinol greatly increased the specific areas and product yield. This can be explained by the high reactivity of phloroglucinol due to its electron density of –OH in 2,4,6 ring position. When the fructose was dehydrated into 5-hydroxymethylfurfural, they can react quickly with the phloroglucinol, which acted as a cross-linker during the reaction of phloroglucinol with carbohydrates and to preserve the porous character of the scaffold after drying [12]. As proven by the SEM images, uniform spheres with smooth surface were obtained with pure fructose as carbon source (FC, Fig. 1a). However, after the addition of phloroglucinol, the final product became irregular, porous material consisting of smaller particles, and the surface was pretty rough (FPC, Fig. 1b). Therefore, porous carbonaceous materials were directly produced from the hydrothermal carbonization of fructose by addition of phloroglucinol, without any further post treatment. Chemical structures of the obtained FPC and FC were analyzed by FT-IR and the results are shown in Fig. 2. The band at 3400 cm-1 is attributed to -OH stretching vibrations, indicating that large numbers of –OH are present on the cabonaceous materials [13]. The band at 1625 cm-1 is attributed to C-C stretching vibrations [14]. It can be found that both FPC and FC contain -OH and C-C groups. The absorption band at 1716 cm-1 is attributed to -COO- group [15, 16] . Obviously, the intensity of -COO- on FPC is significantly higher than that of FC. Elemental composition of the FPC and FC was also analyzed (Table 1). The C and O mass content of FC were 62.6% and 33.7%, respectively, where the O/C ratio was 0.40. After the addition of phloroglucinol, the O/C ratio of FPC increased to 0.66, indicating that phloroglucinol with three –OH was well embedded in the final carbonaceous materials, which was consistent with that reported in reference [12]. The adsorption capacity of the adsorbents was investigated by using a representative antibiotic tetracycline as model compound, and the results are shown in Fig. 3. Adsorption kinetics of tetracycline onto the prepared adsorbent was shown in Fig. S4 in Supporting information and it was observed that the adsorption reached equilibrium within 240 min for both FPC and FC. It can be seen that the
maximum adsorption capacities (qm) were 274.7 and 83.3 mg/g for FPC and FC, respectively. Clearly, the carbonaceous adsorbent prepared from the fructose in the presence of phloroglucinol showed much higher capacity for the adsorption of tetracycline than that derived from pure fructose. This result could attribute to the fact that FPC had much higher BET surface area and higher oxygencontaining functional groups than FC.
3. Conclusion Porous carbonaceous adsorbent was prepared by one-step hydrothermal carbonization with fructose and phloroglucinol as the starting material in hydroalcoholic mixture. The addition of phloroglucinol significantly improved the surface area and pore volume, as well as carboxyl functional groups. The obtained material exhibited a high adsorption capacity of 274.7 mg/g for tetracycline. This work provides a promising method for the preparation of porous carbon materials that have potential applications in the fields such as adsorption, catalysis and energy storage. 4. Experimental 4.1 Preparation and characterization of carbonaceous absorbent In a typical preparation process, 3.60 g of fructose and 0.31 g of phloroglucinol were mixed with a hydroalcoholic mixture consisting of 19 g water and 19 g ethanol (ethanol was added to increase the solubility of phloroglucinol due to the poor solubility of phloroglucinol in pure water). The resulting mixture was vigorous stirred for a few minutes until a clear solution formed. The pH of the mixture was adjusted to 4.5 with HCl. HCl was added into the system to promote the dehydration of fructose into 5hydroxymethylfurfural, which can react quickly with the phloroglucinol and favors the polymerization among fructose, 5hydroxymethylfurfural and phloroglucinol to form the carbonaceous material. After that, the solution was transferred into a 100-mL stainless steel autoclave. The autoclave was heated up to 180 °C and kept at the temperature for 12 h at the autogenous pressure. After that, the solid material was removed from the autoclave, washed with a mixture of water/ethanol, and then with water for three times. After freeze drying for 12 h, the fructose and phloroglucinol based carbon (FPC) was obtained. As a control sample, pure fructose based carbon (FC) was synthesized according to the same way, but in the absence of phloroglucinol. The morphology of carbonaceous adsorbents was observed using a scanning electron microscopy (SEM, S4800, HITACHI). Chemical structures were characterized with a Fourier-transform infrared spectrometer (FT-IR, FTS 6000, Bio-Rad). The surface areas of the adsorbents were determined by nitrogen adsorption-desorption isotherms at the temperature of -196 °C by a multipoint BET method (US8020, HITACHI). Elemental analysis was conducted by Elementar Vario EL cube (Germany). 4.2 Adsorption experiments All of the batch experiments were conducted in 50 mL glass flasks in a shaking table at 120 rpm. Typically, 25 mL tetracycline solutions with different concentrations were mixed with 20 mg adsorbent. The mixtures were shaken on the shaking table at 30 °C for 24 h. After that, the solution was filtered through 0.45 µm membrane filters, and the concentration of the tetracycline in the filtrate was quantified by a UV-vis spectrometer (UV759UV-VIS) at wavelength of 360 nm. The amount of tetracycline adsorbed onto the adsorbent was calculated as follows: (C - C )V (1) qe 0 e m where C0 and Ce are the initial and equilibrium tetracycline concentrations (mg/L), respectively. V is the initial solution volume (L), and m is the mass of the adsorbent. Acknowledgments This work was supported by NSFC (No. 21577073), the Natural Science Foundation of Tianjin (No. 16JCZDJC33700) and Elite Youth program of Chinese Academy of Agricultural Sciences (to Dr. Xin-Hua Qi).
References [1] B. Hu, K. Wang, L.H. Wu, et al., engineering carbon materials from the hydrothermal carbonization process of biomass, Adv. Mater. 22 (2010) 813-828. [2] L. Wei, M. Sevilla, A.B. Fuertes, R. Mokaya, G. Yushin, Hydrothermal carbonization of abundant renewable natural organic chemicals for high-performance supercapacitor electrodes, Adv. Energy. Mater. 1 (2011) 356-361. [3] J. Yang, A. Sudik, C. Wolverton, D.J. Siegel, High capacity hydrogen storage materials: attributes for automotive applications and techniques for materials discovery, Chem. Soc. Rev. 39 (2010) 656-675. [4] K. Fukuhara, K. Nakajima, M. Kitano, et al., Structure and catalysis of cellulose-derived amorphous carbon bearing SO3H Groups, ChemSusChem 4 (2011) 778-784. [5] Y. Wang, R. Yang, M. Li, Z.J. Zhao, Hydrothermal preparation of highly porous carbon spheres from hemp (Cannabis sativa L.) stem hemicellulose for use in energy-related applications, Ind. Crop. Prod. 65 (2015) 216-226. [6] Y.T. Gong, H.Y. Wang, Z.Z. Wei, L. Xie, Y. Wang, An efficient way to introduce hierarchical structure into biomass-based hydrothermal carbonaceous materials, ACS Sustain. Chem. Eng. 2 (2014) 2435-2441. [7] A.J. Romero-Anaya, M. Ouzzine, M.A. Lillo-Ródenas, A. Linares-Solano, Spherical carbons: synthesis, characterization and activation processes, Carbon 68 (2014) 296-307. [8] G.Q. Li, Y.B. Zhang, P. Wu, et al., New phloroglucinol derivatives from the fruit tree syzygium jambos and their cytotoxic and antioxidant activities, J. Agric. Food Chem. 63 (2015) 10257-10262. [9] M. El Hattab, G. Genta-Jouve, N. Bouzidi, et al., unusual phloroglucinol-meroterpenoid hybrids from the brown alga Cystoseira tamariscifolia, J. Nat. Prod. 78 (2015) 1663-1670. [10] C.H. Yao, Y. Shin, L.Q. Wang, et al., Hydrothermal dehydration of aqueous fructose solutions in a closed system, J. Phys. Chem. C 111 (2007) 1514115145. [11] R. Acosta, V. Fierro, A.M. de Yuso, D. Nabarlatz, A. Celzard, Tetracycline adsorption onto activated carbons produced by KOH activation of tyre pyrolysis char, Chemosphere 149 (2016) 168-176. [12] J. Ryu, Y.W. Suh, D.J. Suh, D.J. Ahn, Hydrothermal preparation of carbon microspheres from mono-saccharides and phenolic compounds, Carbon 48 (2010) 1990-1998. [13] D.Y. Song, S. An, B. Lu, Y.H. Guo, J.Y. Leng, Arylsulfonic acid functionalized hollow mesoporous carbon spheres for efficient conversion of levulinic acid or furfuryl alcohol to ethyl levulinate, Appl. Catal. B 179 (2015) 445-457. [14] Y. Wan, H.Y. Wang, Q.F. Zhao, et al., Ordered mesoporous Pd/silica-carbon as a highly active heterogeneous catalyst for coupling reaction of chlorobenzene in aqueous media, J. Am. Chem. Soc. 131 (2009) 4541-4550. [15] X.H. Qi, H.X. Guo, L.Y. Li, R.L. Smith Jr, Acid-catalyzed dehydration of fructose into 5-hydroxymethylfurfural by cellulose-derived amorphous carbon, ChemSusChem 5 (2012) 2215-2220. [16] M. Sevilla, A.B. Fuertes, The production of carbon materials by hydrothermal carbonization of cellulose, Carbon 47 (2009) 2281-2289.
Fig. 1. SEM images of (a) FC and (b) FPC
Transmittance (%)
FPC
FC
-COOH
-OH -C=C
4000
3000
2000
-1
Wavenumber (cm )
Fig. 2. FT-IR spectrum of the FPC and FC
1000
FPC
300
FC
q e (mg/g)
250 200 150 100 50 0 0
1000
2000
3000
4000
5000
C (mg/L) e
Fig. 3. Adsorption isotherms of tetracycline on the prepared FC and FPC materials. (Conditions: 30 °C, pH 3.0, 24 h, adsorbent dosage 20 mg)
Table 1. Physical and chemical properties of the prepared FPC and FC samples Product yield (%)
BET surface area (m2/g)
Total pore volume (cm3/g)
C (%)
H (%)
O (%)
FPC
86
481.7
0.73
50.6
4.9
44.5
FC
33
75.4
0.07
62.6
3.7
33.7
Samples
S1001-8417(17)30005-0 http://dx.doi.org/doi:10.1016/j.cclet.2016.12.026 CCLET 3932
To appear in:
Chinese Chemical Letters
Received date: Revised date: Accepted date:
3-11-2016 6-12-2016 12-12-2016
Please cite this article as: Chen-Xi Bai, Feng Shen, Xin-Hua Qi, Preparation of porous carbon directly from hydrothermal carbonization of fructose and phloroglucinol for adsorption of tetracycline, Chinese Chemical Letters http://dx.doi.org/10.1016/j.cclet.2016.12.026 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.
Original article Preparation of porous carbon directly from hydrothermal carbonization of fructose and phloroglucinol for adsorption of tetracycline Chen-Xi Bai a,b, Feng Shen b, Xin-Hua Qi b, * a b
College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China Agro-Environmental Protection Institute, Chinese Academy of Agricultural Sciences, Tianjin 300191, China
Corresponding author E-mail address: [email protected]
Article info
Article history Received 3 November 2016 Received in revised form 6 December 2016 Accepted 12 December 2016 Available online
Graphical Abstract
Porous carbonaceous material with large surface area (481.7 m2/g) and pore volume (0.73 cm3/g) was prepared directly from hydrothermal carbonization of fructose and phloroglucinol in hydroalcoholic mixture, which provides a green and efficient method to fabricate porous carbonaceous adsorbent that has great potential applications in chemical and environmental fields Abstract
Hydrothermal carbonization of biomass is a promising method to prepare carbonaceous materials. Generally, post physical or chemical activation is necessary to increase surface area and porosity of the carbon. Herein, porous carbonaceous material (FPC) with large surface area (481.7 m2/g) and pore volume (0.73 cm3/g) was prepared directly from hydrothermal carbonization of fructose and phloroglucinol in hydroalcoholic mixture. Structure characteristics of the FPC and its adsorption capacity for a representative antibiotic tetracycline in aqueous solution were investigated. This work provides a green and efficient method to fabricate porous carbonaceous adsorbent that has great potential applications in chemical and environmental fields. Keywords: Fructose Carbon materials Porous materials Adsorption Hydrothermal carbonization
1. Introduction Activated carbon is one of the most commonly used adsorbents due to its easy manipulation and high adsorption capacity. Generally, activated carbons are prepared by pyrolysis and activation of organic compounds. The activation process is normally divided into physical and chemical methods. Both the post-physical and chemical activation can generate carbons with pores and large specific surface area. However, these methods (pyrolysis and activation) have many disadvantages such as high energy consumption, low carbon yield, and large quantities of waste gas emission. Hydrothermal carbonization is a promising route to prepare carbon materials, providing low-cost, low temperature, and environmental friendly production from natural precursors in aqueous solution without the use of toxic reagents [1, 2]. The hydrothermal process involves heat treatment of carbohydrates solution under autogeneous pressure at relatively low temperatures (150-250 °C). The obtained solid carbon has uniform morphology and high content of oxygen-containing groups [3]. So far, carbonaceous materials from hydrothermal carbonization have been widely used in catalysis, adsorption and energy storage [4]. However, the carbon materials derived directly from hydrothermal carbonization of carbohydrates have only limited surface area and almost no porosity [5], greatly affecting the applications of the carbon materials. Thus, after the hydrothermal process, additional post treatment by pyrolysis or activation step at high temperature (>700 °C) are normally essential to introduce porosity within the carbon structure [6, 7]. In this work, porous carbon was synthesized directly from fructose and phloroglucinol in hydroalcoholic mixture via hydrothermal method without any post-treatment. Phloroglucinol herein acted as a cross-linking agent to greatly improve the porosity of the carbon material, which avoid additional post physical or chemical activation process. Fructose is a biomass-derived sugar, and phloroglucinol is the monomeric unit of phlorotannins and can be isolated from the bark of fruit trees [8] or brown algae [9]. The prepared highly porous carbonaceous adsorbents were employed for the adsorption of a representative antibiotics tetracycline in aqueous solution (chemical structure of tetracycline is shown in Fig. S1 in Supporting information), and exhibited excellent performances. 2. Results and discussion. It has been known that the hydrothermal carbonization of pure sugars (glucose, fructose, xylose, etc.) contains two steps: sugars are initially converted into HMF or furfural through intramolecular dehydration reaction, and then the furan compounds are condensed and polymerized to form carbonaceous materials [10]. However, the yield of carbons as well as the surface area is low from the pure sugars, which has limited its application, especially as an adsorbent. To solve this problem, phloroglucinol was employed herein as a co-polymer of fructose during hydrothermal carbonization. It can be seen that the product yield of FPC was 86%, which was 2.6-fold of FC (33%) (Table 1). Based on the N2 adsorption/desorption isotherms of FPC and FC (Fig. S2 in Supporting information), the surface area of FC obtained from hydrothermal treatment of sole fructose was calculated to be 75.4 m2/g. After the addition of phloroglucinol as the co-monomer of fructose in the same system, the BET surface area of the obtained carbonaceous material (FPC) was greatly increased to 481.7 m2/g. The total pore volume of FPC (0.73 cm3/g) was also much higher than that of FC (0.07 cm3/g), indicating that FPC had more abundant pore structure than FC, which was verified from the pore size distribution (Fig. S3 in Supporting information). The surface area and pore volume of FPC herein obtained directly from the hydrothermal carbonization of fructose and phloroglucinol were comparable to that of activated carbons generated by pyrolysis at 600- 800 °C [11]. The above results indicate that the addition of phloroglucinol greatly increased the specific areas and product yield. This can be explained by the high reactivity of phloroglucinol due to its electron density of –OH in 2,4,6 ring position. When the fructose was dehydrated into 5-hydroxymethylfurfural, they can react quickly with the phloroglucinol, which acted as a cross-linker during the reaction of phloroglucinol with carbohydrates and to preserve the porous character of the scaffold after drying [12]. As proven by the SEM images, uniform spheres with smooth surface were obtained with pure fructose as carbon source (FC, Fig. 1a). However, after the addition of phloroglucinol, the final product became irregular, porous material consisting of smaller particles, and the surface was pretty rough (FPC, Fig. 1b). Therefore, porous carbonaceous materials were directly produced from the hydrothermal carbonization of fructose by addition of phloroglucinol, without any further post treatment. Chemical structures of the obtained FPC and FC were analyzed by FT-IR and the results are shown in Fig. 2. The band at 3400 cm-1 is attributed to -OH stretching vibrations, indicating that large numbers of –OH are present on the cabonaceous materials [13]. The band at 1625 cm-1 is attributed to C-C stretching vibrations [14]. It can be found that both FPC and FC contain -OH and C-C groups. The absorption band at 1716 cm-1 is attributed to -COO- group [15, 16] . Obviously, the intensity of -COO- on FPC is significantly higher than that of FC. Elemental composition of the FPC and FC was also analyzed (Table 1). The C and O mass content of FC were 62.6% and 33.7%, respectively, where the O/C ratio was 0.40. After the addition of phloroglucinol, the O/C ratio of FPC increased to 0.66, indicating that phloroglucinol with three –OH was well embedded in the final carbonaceous materials, which was consistent with that reported in reference [12]. The adsorption capacity of the adsorbents was investigated by using a representative antibiotic tetracycline as model compound, and the results are shown in Fig. 3. Adsorption kinetics of tetracycline onto the prepared adsorbent was shown in Fig. S4 in Supporting information and it was observed that the adsorption reached equilibrium within 240 min for both FPC and FC. It can be seen that the
maximum adsorption capacities (qm) were 274.7 and 83.3 mg/g for FPC and FC, respectively. Clearly, the carbonaceous adsorbent prepared from the fructose in the presence of phloroglucinol showed much higher capacity for the adsorption of tetracycline than that derived from pure fructose. This result could attribute to the fact that FPC had much higher BET surface area and higher oxygencontaining functional groups than FC.
3. Conclusion Porous carbonaceous adsorbent was prepared by one-step hydrothermal carbonization with fructose and phloroglucinol as the starting material in hydroalcoholic mixture. The addition of phloroglucinol significantly improved the surface area and pore volume, as well as carboxyl functional groups. The obtained material exhibited a high adsorption capacity of 274.7 mg/g for tetracycline. This work provides a promising method for the preparation of porous carbon materials that have potential applications in the fields such as adsorption, catalysis and energy storage. 4. Experimental 4.1 Preparation and characterization of carbonaceous absorbent In a typical preparation process, 3.60 g of fructose and 0.31 g of phloroglucinol were mixed with a hydroalcoholic mixture consisting of 19 g water and 19 g ethanol (ethanol was added to increase the solubility of phloroglucinol due to the poor solubility of phloroglucinol in pure water). The resulting mixture was vigorous stirred for a few minutes until a clear solution formed. The pH of the mixture was adjusted to 4.5 with HCl. HCl was added into the system to promote the dehydration of fructose into 5hydroxymethylfurfural, which can react quickly with the phloroglucinol and favors the polymerization among fructose, 5hydroxymethylfurfural and phloroglucinol to form the carbonaceous material. After that, the solution was transferred into a 100-mL stainless steel autoclave. The autoclave was heated up to 180 °C and kept at the temperature for 12 h at the autogenous pressure. After that, the solid material was removed from the autoclave, washed with a mixture of water/ethanol, and then with water for three times. After freeze drying for 12 h, the fructose and phloroglucinol based carbon (FPC) was obtained. As a control sample, pure fructose based carbon (FC) was synthesized according to the same way, but in the absence of phloroglucinol. The morphology of carbonaceous adsorbents was observed using a scanning electron microscopy (SEM, S4800, HITACHI). Chemical structures were characterized with a Fourier-transform infrared spectrometer (FT-IR, FTS 6000, Bio-Rad). The surface areas of the adsorbents were determined by nitrogen adsorption-desorption isotherms at the temperature of -196 °C by a multipoint BET method (US8020, HITACHI). Elemental analysis was conducted by Elementar Vario EL cube (Germany). 4.2 Adsorption experiments All of the batch experiments were conducted in 50 mL glass flasks in a shaking table at 120 rpm. Typically, 25 mL tetracycline solutions with different concentrations were mixed with 20 mg adsorbent. The mixtures were shaken on the shaking table at 30 °C for 24 h. After that, the solution was filtered through 0.45 µm membrane filters, and the concentration of the tetracycline in the filtrate was quantified by a UV-vis spectrometer (UV759UV-VIS) at wavelength of 360 nm. The amount of tetracycline adsorbed onto the adsorbent was calculated as follows: (C - C )V (1) qe 0 e m where C0 and Ce are the initial and equilibrium tetracycline concentrations (mg/L), respectively. V is the initial solution volume (L), and m is the mass of the adsorbent. Acknowledgments This work was supported by NSFC (No. 21577073), the Natural Science Foundation of Tianjin (No. 16JCZDJC33700) and Elite Youth program of Chinese Academy of Agricultural Sciences (to Dr. Xin-Hua Qi).
References [1] B. Hu, K. Wang, L.H. Wu, et al., engineering carbon materials from the hydrothermal carbonization process of biomass, Adv. Mater. 22 (2010) 813-828. [2] L. Wei, M. Sevilla, A.B. Fuertes, R. Mokaya, G. Yushin, Hydrothermal carbonization of abundant renewable natural organic chemicals for high-performance supercapacitor electrodes, Adv. Energy. Mater. 1 (2011) 356-361. [3] J. Yang, A. Sudik, C. Wolverton, D.J. Siegel, High capacity hydrogen storage materials: attributes for automotive applications and techniques for materials discovery, Chem. Soc. Rev. 39 (2010) 656-675. [4] K. Fukuhara, K. Nakajima, M. Kitano, et al., Structure and catalysis of cellulose-derived amorphous carbon bearing SO3H Groups, ChemSusChem 4 (2011) 778-784. [5] Y. Wang, R. Yang, M. Li, Z.J. Zhao, Hydrothermal preparation of highly porous carbon spheres from hemp (Cannabis sativa L.) stem hemicellulose for use in energy-related applications, Ind. Crop. Prod. 65 (2015) 216-226. [6] Y.T. Gong, H.Y. Wang, Z.Z. Wei, L. Xie, Y. Wang, An efficient way to introduce hierarchical structure into biomass-based hydrothermal carbonaceous materials, ACS Sustain. Chem. Eng. 2 (2014) 2435-2441. [7] A.J. Romero-Anaya, M. Ouzzine, M.A. Lillo-Ródenas, A. Linares-Solano, Spherical carbons: synthesis, characterization and activation processes, Carbon 68 (2014) 296-307. [8] G.Q. Li, Y.B. Zhang, P. Wu, et al., New phloroglucinol derivatives from the fruit tree syzygium jambos and their cytotoxic and antioxidant activities, J. Agric. Food Chem. 63 (2015) 10257-10262. [9] M. El Hattab, G. Genta-Jouve, N. Bouzidi, et al., unusual phloroglucinol-meroterpenoid hybrids from the brown alga Cystoseira tamariscifolia, J. Nat. Prod. 78 (2015) 1663-1670. [10] C.H. Yao, Y. Shin, L.Q. Wang, et al., Hydrothermal dehydration of aqueous fructose solutions in a closed system, J. Phys. Chem. C 111 (2007) 1514115145. [11] R. Acosta, V. Fierro, A.M. de Yuso, D. Nabarlatz, A. Celzard, Tetracycline adsorption onto activated carbons produced by KOH activation of tyre pyrolysis char, Chemosphere 149 (2016) 168-176. [12] J. Ryu, Y.W. Suh, D.J. Suh, D.J. Ahn, Hydrothermal preparation of carbon microspheres from mono-saccharides and phenolic compounds, Carbon 48 (2010) 1990-1998. [13] D.Y. Song, S. An, B. Lu, Y.H. Guo, J.Y. Leng, Arylsulfonic acid functionalized hollow mesoporous carbon spheres for efficient conversion of levulinic acid or furfuryl alcohol to ethyl levulinate, Appl. Catal. B 179 (2015) 445-457. [14] Y. Wan, H.Y. Wang, Q.F. Zhao, et al., Ordered mesoporous Pd/silica-carbon as a highly active heterogeneous catalyst for coupling reaction of chlorobenzene in aqueous media, J. Am. Chem. Soc. 131 (2009) 4541-4550. [15] X.H. Qi, H.X. Guo, L.Y. Li, R.L. Smith Jr, Acid-catalyzed dehydration of fructose into 5-hydroxymethylfurfural by cellulose-derived amorphous carbon, ChemSusChem 5 (2012) 2215-2220. [16] M. Sevilla, A.B. Fuertes, The production of carbon materials by hydrothermal carbonization of cellulose, Carbon 47 (2009) 2281-2289.
Fig. 1. SEM images of (a) FC and (b) FPC
Transmittance (%)
FPC
FC
-COOH
-OH -C=C
4000
3000
2000
-1
Wavenumber (cm )
Fig. 2. FT-IR spectrum of the FPC and FC
1000
FPC
300
FC
q e (mg/g)
250 200 150 100 50 0 0
1000
2000
3000
4000
5000
C (mg/L) e
Fig. 3. Adsorption isotherms of tetracycline on the prepared FC and FPC materials. (Conditions: 30 °C, pH 3.0, 24 h, adsorbent dosage 20 mg)
Table 1. Physical and chemical properties of the prepared FPC and FC samples Product yield (%)
BET surface area (m2/g)
Total pore volume (cm3/g)
C (%)
H (%)
O (%)
FPC
86
481.7
0.73
50.6
4.9
44.5
FC
33
75.4
0.07
62.6
3.7
33.7
Samples