Removal of noxious materials such as heavy metal ions (which are hazardous above certain ppm concentration) from wastewater is one of the biggest environmental challenges that suffers the Downloaded by [New York University] at 19:39 22 June 2015 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 economy nowadays. On the basis of their versatility, environmental friendliness, the adsorption was proved to be a most economical and efficient technology, which is used extensively for their removal from the aqueous media. Among the various developed adsorbents used so far, carbon nanotubes (CNTs) show a unique impact on the fast adsorption and rapid removal of noxious impurities from the aqueous source. CNTs festooned on the sources like activated carbon, nanoparticles and nanocomposities enhanced the efficiency and potential of the adsorbent. Due to their unique structural, electronic, optoelectronic, semiconductor, as well as mechanical, chemical and physical properties, they have been extensively used to remove heavy metals in wastewater treatment. The adsorption mechanisms is majorly contributed by the chemical interactions between the metal ions and the functional groups present on the surface of the CNTs.Greater the surface area more will be the number of reducing groups hence more attributable to better CNT sorption performances.Graphical Abstract: schematic for interaction of carbon nanotube with heavy metal ions in aqueous solution
ABSTRACT:The effects of different solid substrates, including carbon nanofibers (CNFs), activated carbon, alumina, silica, molecular sieves, and poly(N-vinylpyrrolidione) (PVP), were compared for the high-pressure synthesis of polytetrafluoroethylene [PTFE or (CF 2 ) n ] nanoparticles via the adsorption of thermally synthesized tetrafluoroethylene (C 2 F 4 ) as the monomer. Scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis (TGA) were used for the characterization of the PTFE nanoparticles on different solid substrates. The results demonstrate that the average diameters of the PTFE nanoparticles were about 90 nm for the CNFs, 130 nm for PVP, 150 nm for alumina, and about 200 nm for silica. Also, TGA showed that the amounts of PTFE nanoparticles synthesized on each solid substrate were 3.53 6 0.09% for CNFs, 2.31 6 0.10% for PVP, 2.11 6 0.12% for silica, and 0.97 6 0.16% for alumina. Depending on the active surface area and the morphology of nanomaterials, such as CNFs, different capacities were evaluated for each solid support in the formation of the PTFE nanoparticles. The quantities and the size of the synthesized PTFE nanoparticles relied on the characteristics of the solid substrate.
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