The Preparation And Adsorptivity Of Soluble Starch-functionalized Carbon Nanotube Composites

Since their discovery,carbon nanotubes (CNTs) have attracted great attentions all over the world, due to their intrinsicstructures (e.g.large aspect ratio and chirality), outstanding properties (e.g.electrical, mechanical,optical properties) as well as their promise potential applications in the area of material chemistry. However, CNTs are not solubilized in almost any solvents, which hinderes their applications. So it is very important to functionalize the carbon nanotubes in order to improve their dispersibility in solvents and matrics.In this paper, a novel starch-grafted multiwalled carbon nanotubes (St-g- MWCNT) was prepared through covalently grafting a biocompatible polymer St onto the surfaces of MWCNT. On the basis of Fourier transform infrared spectroscopy (FT-IR), we can conclude that the St is covalently grafted onto the MWCNT. Ultrviolet-visible spectroscopy (UV-vis) shows a sharp absorption peak at about 265nm, which can be attributed to the characteristic absorption of MWCNT. Interestingly, the observed absorption peak in St-g-MWCNT solution depends on the solution concentrations in a linear fashion, obeying the Lambert-Beer's law. A core-shell nanostructure can be observed by transmission electron microscopy (TEM), indicating that the nanotubes are coated with polymer chains. Thermogravimetry analysis (TGA) provids quantitative information on the grafted degree of starch.The covalent modification overcomes the issues of poor interfacial bonding between the two phases, so that carbon nanotubes have good solubility in water.In order to make carbon nanotubes be used in water treatment, a composite material of carbon nanotube/Fe₃O₄ was further prepared, so that magnetic carbon nanotubes are easy to operate in practical applications, which is a significant savings in manpower and resources. Transmission electron microscopy and X-ray analysis show that the Fe₃O₄ crystal particles on the St-g-MWCNT is smaller with uniform distribution, while the Fe₃O₄ crystal particles of acidified carbon nanotubes(p- MWCNT) is larger and cluster state. This may be related to the starch molecular chains on the surface of carbon nanotubes. The adsorption of methyl orange(MO), methylene blue(MB), and heavy metal ions (Cr³⁺, Pb²⁺, Cu²⁺) using the carbon nanotube/Fe₃O₄ adsorbent is studied, the experimental results show that the adsorption capacity of carbon nanotubes is significantly increased. The study of kinetics reveals that the pseudo-second-order kinetic adsorption model is suitable for describing the adsorption of MO and MB on the St-g-MWCNT and p-MWCNT. These results show that carbon nanotubes grafted starch significantly increased its water-soluble compared to acidified carbon nanotubes, and this modified method does not seriously damage the carbon nanotubes.