Elsevier

Carbohydrate Polymers

Volume 88, Issue 1, 17 March 2012, Pages 61-67
Carbohydrate Polymers

Facile synthesis of three-dimensional chitosan–graphene mesostructures for reactive black 5 removal

https://doi.org/10.1016/j.carbpol.2011.11.065Get rights and content

Abstract

In this paper, a hydrophilic and biocompatible three-dimensional (3D) chitosan–graphene mesostructures with large specific surface area (603.2 m2 g−1) and unique mesoporosity were prepared by simply thermal treatment of graphene oxide nanosheets and chitosan. By starting from waste sugarcane bagasse derived graphite and chitosan, the resulted 3D nanocomposites possess superior competitiveness in biocompatibility, renewable resource recycling, cheapness and specific area. The composites were systematically characterized by a variety of analytical methods. Investigations showed that the 3D mesostructures can be used to remove reactive black 5 (RB5) from aqueous solution. A removal efficiency of 97.5% can be achieved readily at initial RB5 concentrations of 1.0 mg/mL. These results indicate the 3D mesostructures can be used to treat the industrial effluent or contaminated natural water, providing novel insights for the fabrication of 3D functionalized graphene with various building blocks for broad potential applications.

Highlights

► Three-dimensional graphene mesostructures with large specific area were prepared. ► Graphene oxide was prepared from waste sugarcane bagasse derived graphite. ► The 3D material holds advantages in mesoporous, biocompatibility and cheapness. ► The pristine properties of graphene can be preserved in this 3D mesostructures. ► The material show high efficiency for reactive black 5 removal, a typical azo dye. ► This 3D material holds great potentials in treating the industrial effluent etc.

Introduction

Graphene, a one-atom-thick planar carbon material with superior chemical stability, large surface-to-volume ratio, tunable band gap, good electronic, mechanical and thermal stability, is currently attracting considerable attentions (Bunch et al., 2007, Geim, 2009, Li et al., 2008, Stoller et al., 2008). Various methodologies have been developed to fabricate graphene, which include Scotch tape (Novoselov et al., 2005), epitaxial growth (Reina et al., 2008) and chemical reduction of graphene oxide etc. (Xu, Bai, Lu, Li, & Shi, 2008). All these approaches are suitable to prepare traditional graphene nanosheets, while in some important areas such as energy-storage materials, liquid crystal devices, field effect transistors, biosensors, catalysts as well as adsorbents for water treatment (Allen et al., 2008, Li et al., 2008, Wu et al., 2008), graphene based materials with unique pore structures and significantly enhanced specific surface area are urgently needed to achieve high electrical or catalytic performances. Due to gradual decrease of its hydrophilic character, conventional graphene nanosheets are easily aggregated and even restacked to form graphite when they are used with bulk-quantity (Du et al., 2008, Wang et al., 2008), the pristine properties of graphene would be therefore hindered.

Fortunately, previous works show that graphene materials with spatial mesostructures would avoid such inferior possibility of graphene (Fan et al., 2010, Lee et al., 2010). In recently years, three-dimensional mesoporous carbon materials have been fabricated via hard templates methods or soft templates methods (e.g. self-assembly) (Chen et al., 2011, Fan et al., 2010, Guo et al., 2010a, Guo et al., 2010b, Lee et al., 2010, Liang et al., 2008, Sun et al., 2009, Xu et al., 2010a, Xu et al., 2010b). However, these templating routes suffer disadvantages related to high costs and tedious synthetic procedures. Moreover, such conventional approaches to the production of 3D structures are usually tended to use non-biocompatible graphene materials. Therefore, its necessary to develop a template-free approach for biocompatible 3D mesoporous graphene-based material for broad-scientific research and practical applications. Previous work shows that graphene functionalized with different polymers or ionic liquid would be beneficial for constructing biocompatible 3D mesoporous carbon material (Allen et al., 2008, Guo et al., 2010a, Guo et al., 2010b, Xu et al., 2010a). Chitosan (CS), the second most abundant natural biopolymer on earth (Kawahara et al., 2003, Macquarrie and Hardy, 2005), possesses excellent film-forming ability, biocompability, biodegradable, good adhesion, non-toxicity, and susceptibility to chemical modification due to the presence of plentiful amino groups and hydroxyl groups. Based on these specific properties of CS, it is reasonable to speculate that both the hydrophilicity and biocompatibility of graphene could be improved by non-covalent functionalization of graphene with CS, the pristine properties of graphene and CS would be therefore preserved.

Wastewater from industries is highly colored and the residual azo dyes in it are seriously concerned for their adverse effects to human beings and the environment (Crini, 2006, Forgacs et al., 2004). Many technologies have been developed for the azo dyes removal from aquatic environment, including physical, chemical and biological approaches (Ahmad and Puasa, 2007, Stolz, 2001). However, most chemical and biological methods with high cost or low degradation efficiency are rarely used in the actual treatment processes (Crini, 2006, Ghoreishi and Haghighi, 2003), some physical adsorption approaches also encountered low removing efficiencies of dye (Crini, 2006, Forgacs et al., 2004).

In the past several years, graphene and graphene-based functional materials have caused increasing interests in environmental applications due to its large surface area, excellent mechanical strength and high electrical conductivity (Chandra et al., 2010, Yang et al., 2010). For example, we have prepared a chemically bonded TiO2 (P25)-graphene nanocomposites photocatalyst, which possessed great adsorptivity of dyes, extended light absorption range, and efficient charge separation properties simultaneously and demonstrated significant advancement over bare P25 in the photodegradation of methylene blue dye under both UV and visible light irradiation (Zhang, Lv, Li, Wang, & Li, 2010).

Developing hydrophilic and biocompatible 3D structures graphene composites with large specific surface area and unique mesoporosity by simply thermal method would expand its significance in the area of environmental applications. Herein, a template-free approach is used to controllably synthesize the novel 3D-CSGR mesostructures with large specific surface area and pronounced mesoporosity by simply thermal treatment of the mixture of graphene nanosheets and chitosan. The physcicochemical properties of the 3D material are systematically characterized by Fourier transform infrared (FTIR) spectrometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD) spectroscopy, selected area electron diffraction (SAED) patterns and Brunauer–Emmett–Teller (BET) analysis. The 3D mesostructures were used as an effective absorbent for the decoloration of reactive black 5 (RB5, Scheme 1) with superior performance (Barron-Zambrano, Szygula, Ruiz, Sastre, & Guibal, 2010), which is competitive to commercial absorbents. Moreover, this hydrophilic and biocompatible 3D structures graphene composites with large specific surface area (603.2 m2 g−1) and unique mesoporosity show also broad prospects in catalyst, solar cell, lithium ions battery and biosensors.

Section snippets

Materials

Graphite powder (99.99995%, 325 mesh) was purchased from Alfa Aesar. Chitosan was supplied by National Medicine Group, Shanghai, China (the degree of deacetylation was 90%, and the molecular weight was 125,000 g mol−1). The chitosan was ground and sieved, and the 0–125 μm fraction was used for experiments. Sugarcane bagasse (SB) was obtained from Liangci Manufacturing Co. Ltd. of the Guangxi Zhuang Autonomous Region of China. Sugarcane bagasse was activated by physical activation, which involved

Synthesis and characterization of 3D chitosan–graphene mesostructures

Chitosan is widely used in environmental applications for dye removal owing to its easy degradation, biocompability, biodegradable, low price and large surface area (Barron-Zambrano et al., 2010, Kawahara et al., 2003, Macquarrie and Hardy, 2005). Successful surface modification of grapheme with chitosan by nonfunctional method can combine advantageous properties of graphene and chitosan in environmental applications without loss of their inherit characteristics. To expend its price

Conclusion

In conclusion, we have developed a novel and simple thermal method to prepare 3D chitosan–graphene nanocomposites with large specific surface area and unique mesoporosity. By starting from waste sugarcane bagasse derived graphite and chitosan, the resulted composites possess competitiveness in renewable resource recycling and environmental applications. The mesocomposites exhibit high dye-adsorption capacity, which were used to RB5 from aqueous solution. Besides high surface area and unique

Acknowledgement

This work was financially supported by the Guangxi Zhuang Autonomous Region Science Foundation of China (No. 200908193).

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