**Adsorption of Methylene Blue on Multi-Walled Carbon Nanotubes in Sodium Alginate Gel Beads**

Fang-Chang Tsai, Ning Ma, Lung-Chang Tsai, Chi-Min Shu, Tao Jiang, Hung-Chen Chang, Sheng Wen, Chi Zhang, Tai-Chin Chiang, Yung-Chuan Chu, Wei-Ting Chen, Shih-Hsin Chen, Han-Wen Xiao, Yao-Chi Shu and Gang Chang

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/50714

**1. Introduction**

[131] Pandelia, M., Fourmond, V., Tron, P., Lojou, E., Bertrand, P., Léger, C., Giudici-Orti‐ coni, M. T., & Lubitz, W. (2010). Membrane-Bound Hydrogenase I from the Hyper‐ thermophilic Bacterium *Aquifex aeolicus:* Enzyme Activation, Redox Intermediates and Oxygen Tolerance. *Journal of the American Chemical Society*, 132(20), 6991-7004.

[132] Fritsch, J., Scheerer, P., Frielingsdorf, S., Kroschinsky, S., Friedrich, B., Lenz, O., & Spahn, C. M. T. (2011). The crystal structure of an oxygen-tolerant hydrogenase un‐

[133] Krishnan, S., & Armstrong, F. A. (2012). Order-of-magnitude enhancement of an en‐ zymatic hydrogen-air fuel cell based on pyrenyl carbon nanostructures. *Chemical Sci‐*

[134] Vincent, K., Cracknell, J., Clark, J., Ludwig, M., Lenz, O., Friedrich, B., & Armstrong, F. (2006). Electricity from low-level H2 in still air- an ultimate test for an oxygen toler‐

[135] Wait, A., Parkin, A., Morley, G., dos, Santos. L., & Armstrong, F. (2010). Characteris‐ tics of enzyme-based hydrogen fuel cells using an oxygen-tolerant hydrogenase as

[136] Ciaccafava, A., de Poulpiquet, A., Techer, V., Giudici-Orticoni, M. T., Tingry, S., In‐ nocent, C., & Lojou, E. (2012). An innovative powerful and mediatorless H2/O2 bio‐ fuel cell based on an outstanding bioanode. *Electrochemistry Communications*, 23,

[137] Infossi, P., Lojou, E., Chauvin, J. P., Herbette, G., Brugna, M., & Giudici-Orticoni, M. T. (2010). *Aquifex aeolicus* membrane hydrogenase for hydrogen bioxidation: role of lipids and physiological partners in enzyme stability and activity. *International Jour‐*

[138] Reuillard, B., Le Goff, A., Agnès, A., Zebda, A., Holzinger, M., & Cosnier, S. (2012). Direct electron transfer between tyrosinase and multi-walled carbon nanotubes for bioelectrocatalytic oxygen reduction. *Electrochemistry Communications*, 20, 19-22.

[139] Durand, F., Kjaergaard, C., Suraniti, E., Gounel, S., Hadt, R., & Solomon, E. (2012). Mano N Bilirubin oxidase from *Bacillus pumilus*: A promising enzyme for the elabora‐ tion of efficient cathodes in biofuel cells. *Biosensors Bioelectronics*, 35(1), 140-146.

the anodic catalyst. *Journal of Physical Chemistry C*, 114(27), 12003-12009.

covers a novel iron-sulphur centre. Nature NIL\_134., 479(7372), 249.

ant hydrogenase. *Chemistry Communications*, 5033-5035.

*nal of Hydrogen Energy*, 35(19), 10778-10789.

*ence*, 3(4), 1015-1023.

466 Syntheses and Applications of Carbon Nanotubes and Their Composites

25-28.

Surface water contamination by pollutants is common in highly industrialized countries due to direct discharge of industrial effluents into bodies of water or precipitation of air-borne pollutants into surface water [Murakamia et. al., 2008]. Dyes from the pollutants released along with industrial effluents are easily detected because of their inherently high visibility, meaning that concentrations as low as 0.005 mg/L can easily be detected and capture the at‐ tention of the public and the authorities [Ray et. al., 2003, Ray et. al., 2002]. Apart from the aesthetic problems caused by dyes, the greatest environmental concern with dyes is their ab‐ sorption and reflection of sunlight entering the water, which interferes with the growth of bacteria, such that bacteria levels are insufficient to biologically degrade impurities in the water [Pierce, 1994. Ledakowicz et. al., 2001]. Methylene blue (MB) and methyl violet are two common dyes that have been shown to induce harmful effects on living organisms dur‐ ing short periods of exposure [Hameed et. al., 2009]. Oral ingestion of MB results in a burn‐ ing sensation and may cause nausea, vomiting, diarrhea, and gastritis. The accidental consumption of large dose induces abdominal and chest pain, severe headache, profuse sweating, mental confusion, painful micturation, and methemoglobinemia [Yasemin et. al., 2006]. Inhalation of methyl violet may cause irritation to the respiratory tract, vomiting, di‐ arrhea, pain, headaches, and dizziness; long-term exposure may cause damage to the mu‐ cous membranes and gastrointestinal tract [Allen & Koumanova, 2005]. The majority of dyes

© 2013 Tsai et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Tsai et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

in this class are synthetic and usually composed of aromatic rings, which makes them carci‐ nogenic and mutagenic [Ghosh & Bhattacharyya, 2002. Chen et. al., 2003]; they are inert and non-biodegradable when discharged into waste streams [Mittal & Gupta, 1996, Seshadri et. al., 1994]. With the social and economic development, the environmental consciousness of citizens and governing agencies was enhanced. Environmental pollution issues have gar‐ nered a considerable amount of attention throughout the world [Renmin et. al., 2005]. MB is a good representative of organic dyes that are difficult to degrade and substantially damage the environment due to their toxicity and dark color [Ho et. al., 2005].

**2. Experimental**

distilled water.

**Figure 1.** The preparation process of the SA/MWCNT composite gel beads.

**2.1. Materials and methods**

The SA, MB, and MWCNT were used as received from Fuchen Chemical Reagents Factory, Tianjin, China and Nanotechnologies Port Co., Ltd., Shenzhen, China. The MWCNTs was treated with a mixture of sulfuric and nitric acid under ultrasonic vibration, as seen in Table 1. According to the series reaction time in Table 1, the optimized ratio of the MWCNT to acid mixture is 3:1 by volume. Ultrasonic treatment was applied for the duration of varying reaction times. Filtration was conducted with a micropore filter and sand core filter. Pure de–ionized water (pure DI water) was used to rinse the filtrate until the pH of the aqueous solution was neutral. The compositions of the SA, MWCNT, and SA/MWCNT series speci‐ mens prepared in this study are summarized in Table 2. Ten milliliters of an aqueous solu‐ tion of SA/MWCNT was added drop-wise to 50 mL of calcium chloride (10%, w/v) aqueous solution for 20 min, followed by the sampling of supernatant at the specified time intervals. The gel particles were pre-consolidated under a pressure of 8–30 kPa in a consolidation cell with an inner diameter of 2.0–3.0 mm to produce a packed gel bed to determine their ex‐ pression characteristics. The schematic evolution of the SA and MWCNT in the microsphere, as a function of the calcium chloride, is shown in Figure 1. Other supplementary agents were of analytical grade (purity > 99.8 mass%) and all solutions were prepared with double

Adsorption of Methylene Blue on Multi-Walled Carbon Nanotubes in Sodium Alginate Gel Beads

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Since carbon nanotube (CNT) was first discovered by S. Ijima in 1991, it has become an aca‐ demic research subject of great interest [Olson, 1994]. CNT is the thinnest tubular structure humans can presently fabricate. It is lightweight and has high strength, high toughness, flex‐ ibility, high surface area, high thermal conductivity, and good electric conductivity and is chemically stable [Baughman et. al., 2002, Thostenson et. al., 2001, Banerjee et. al., 2005]. To fully exploit the superior mechanical, electrical and optical properties of multi-walled car‐ bon nanotube (MWCNT), dispersion and adhesion to a polymeric matrix is a key issue [Iiji‐ ma, 1991]. Both the dispersibility and matrix adhesion of MWCNT can be improved either by covalent or noncovalent functionalization. For covalent functionalization, several ap‐ proaches studied, each having its advantages and drawbacks; examples of such methods in‐ clude wet chemical methods with typical treatment times of up to 24 h [Sahoo et. al., 2010, Liu et. al., 1998, Chen et. al., 1998], treatment in air at elevated temperatures [Tsai et. al., 2010, Ajayan et. al., 1993], by ozone oxidation [Ago et. al., 1999, Mawhinney et. al., 2000] and treatment with low-pressure plasmas [Simmons et. al., 2006, Tseng et. al., 2006, Chen et. al., 2010, Zschoerper et. al., 2009].

Alginate is a collective term for a family of exopolysaccharides produced mainly by brown seaweeds. It has been widely used in the food, biomedical, pharmaceutical, and sewage-treat‐ ment industries, preferentially as sodium alginate due to its solubility in cold water. In mo‐ lecular terms, alginate is composed of (1–4)-linked b-D-mannuronic acid (M) unbranched binary copolymer and a-L-guluronic acid (G) monomer residue, constituting M-, G-, and MG sequential block structures [Chen et. al., 2009]. Most applications that use alginate are based on its gel-forming ability through cation binding: the transition from water-soluble sodium alginate (SA) to water insoluble calcium alginate, for example. Divalent cations preferential‐ ly bind toward the G-block rather than the M-block [Moe et. al., 1995, Braccini et. al., 1999]. The composition of monomers and their sequential character (i.e., blackness) affects the gel‐ atin behavior of alginate. In the presence of Ca2+, G-rich samples generally form hard and brit‐ tle gels while M-rich samples from soft and elastic gels [Braccini & Perez, 2001, Courtois et. al., 1993, Thakur et. al., 1997, Pe´rez et. al., 1996]. The ''egg-box'' model has been accepted as a general model to describe gel formation [Morris et. al., 1978, Thom et. al., 1985]. Alginate is an excellent polymer flocculant and has been widely used in wastewater treatment.

This study reports for the first time the effect of the carboxylation method on CNT structure and property. The results can be used as reference for selecting the carboxylation method. Furthermore, the applicability of a new adsorbent, SA and MWCNT and the SA/MWCNT composite, for the sorption of MB dyes from an aqueous solution were investigated.
