Catalytic carbonization of polypropylene into cup-stacked carbon Cross Mark nanotubes with high performances in adsorption of heavy metallic ions and organic dyes

A one-pot approach was demonstrated to effectively synthesize cup-stacked carbon nanotubes (CS-CNTs) through carbonization of polypropylene (PP) under the combined catalysis of halogenated compound and NiO at 700 degrees C. The effect of halogenated compound on the morphology, microstructure, phase structure and thermal stability of the resultant CS-CNTs was studied by scanning electron microscope, transmission electron microscope (TEM), high-resolution TEM, X-ray diffraction, Raman spectroscopy and thermal gravimetric analysis. Long, straight and surface-smooth CS-CNTs with graphene nanosheets oblique to CS-CNT axis at the angle of 21-25 degrees were obtained when a low content of halogenated compound was added. The synergetic catalytic efficiency of combined catalysts in the carbonization of PP into CS-CNTs followed in the sequence: fluorinated compound/NiO << chlorinated compound/NiO < bromated compound/NiO < iodated compound/NiO. Furthermore, the effect of halogenated compound on the degradation products of PP was analyzed. A low content of halogenated compound facilitated the formation of a large amount of light hydrocarbons with a small amount of aromatics, which promoted the coalescence and reconstruction of NiO catalyst into rhombic shape. The rhombic NiO then catalyzed the light hydrocarbons and aromatics into CS-CNTs. Finally, the resultant CS-CNTs were oxidized to prepare acid-treated CS-CNTs, which showed high performances in adsorption of heavy metallic ions and organic dyes. The adsorption kinetic and isotherms by acid-treated CS-CNTs were also studied. (C) 2014 Elsevier B.V. All rights reserved.