Growth of carbon nanotube on micro-sized Al 2 O 3 particle and its application to adsorption of metal ions
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Jao-Jia Horng and Cheng-Kuo Tsai Department of Safety, Health, and Environmental Engineering, National Yunlin University of Science and Technology, Douliou, Yunlin, Taiwan 640 (Received 10 November 2005; accepted 6 February 2006)
Carbon nanotubes (CNTs) were grown on micron-sized Al2O3 particles in an atmosphere of methane and hydrogen at 700 °C under the catalysis of Fe–Ni nanoparticles that had been deposited on the surface of Al2O3 particles by an electroless plating technique. The individual and competitive adsorption capacities of Pb2+, Cu2+, and Cd2+ from aqueous solution by CNTs on Al2O3 particles were studied. The results showed that the adsorption behavior of these metal ions by as-grown CNTs on Al2O3 particles is in good agreement with the Langmuir adsorption model. The maximum individual adsorption capacities of Pb2+, Cu2+, and Cd2+ from water by as-grown CNTs on Al2O3 particles are 62.50, 27.03, and 9.30 mg/g, respectively. The CNTs on Al2O3 particles have promising potential applications in removing soluble heavy metals from aqueous solutions.
I. INTRODUCTION
Since carbon nanotubes (CNTs) were discovered, their applications in various fields have been studied widely and intensely. CNT’s adsorption capacity for various substances is one of its attractive characteristics. CNTs can be used as effective adsorbents for metals,1–5 gas molecules,6,7 fluorides,8 hydrogens,9,10 and others. Because heavy metals in wastewater are very dangerous to human health, there are many methods developed to remove them from water; such as ion exchange, chemical precipitation, electrolysis, reverse osmosis, and adsorption, etc.11–15 Among these methods, adsorption is the most widely used technique. Various materials have been found and studied for adsorption of heavy metals, such as activated carbon, aquatic plants, minerals, chitin, chelating resin, activated sludge, organic polymers, biopolymer and carbon nanotubes, etc.2,16–24 The experimental results1–4 indicate that CNTs are promising candidate materials for the removal of heavy metals from wastewater. Additionally, the use of metals and bimetals, such as Fe, Fe/Ni and others, has been extensively studied for the treatment of groundwater containing toxic chlorinated
organics.25–38 Because a film of iron oxide will form on the surface of iron particles due to the increase of pH value in the dechlorination process, the dechlorination capacity of Fe is gradually lowered. Because the Ni in Fe/Ni bimetals acts as a catalyst in dechlorination and anti-corrosivity in water, and the Fe itself possesses ability for dechlorination, Fe/Ni bimetals can be used as effective dechlorination materials. When CNTs are used as adsorbents for heavy metals and Fe/Ni particles are used as the dechlorination material, the larger their surface area, the greater their efficiency. However, when the dimensions of CNTs and Fe/Ni particles are reduced to nano-size, they are easily washed away in groundwater. Hence, a carrier for supporting CNTs and Fe/Ni particles and reducing their loss is nec
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