Adsorption behavior of heavy metal ions by carbon nanotubes grown on microsized Al2O3 particles

Carbon nanotubes (CNTs) were grown on the surface of microsized Al2O3 particles in CH4 atmosphere at 700°C under the catalysis of Fe-Ni nanoparticles. The CNTs on Al2O3 were used for adsorbing Pb2+, Cu2+, and Cd2+ from the solution and the results were compared with active carbon powders, commercial carbon nanotubes, and Al2O3 particles. The as-grown CNTs/Al2O3 have demonstrated extraordinary absorption capacity with further treatment or oxidation, as well as hydrophilic ability that other CNTs lacked. The adsorption capacity of CNTs on Al2O3 is superior to other adsorbents and the preference order of adsorption on composite Al2O3 is Pb2->Cu2+>Cd2+. It seemed that the adsorption of those Pb2+, Cu2+, and Cd2+ did not change the surface properties of composite particles. The adsorption behaviors of Pb2+, Cu2+, and Cd2+ by CNTs on Al2O3 match well with the Langmuir isothermal adsorption model and the second order kinetic model. The calculated saturation amount adsorbed by 1 g of CNTs on Al2O3 are 67.11, 26.59, and 8.89 mg/g for Pb2-, Cu2+, and Cd2+ in single adsorption test, respectively.