Preparation And Application Of Magnetic Carbon Nanotubes And Thiolated Porous Chitosan

Benzo[a]pyrene is one of the most carcinogenic polycyclic aromatic hydrocarbons. As typical heavy metals, lead, mercury, chromium, arsenic, cadmium and copper are also harmful to health. Human would be exposed to heavy metals through polluted environment, food intake and drug abuse. In recent years, benzo[a]pyrene levels in food have attracted more and more attention. In the process of tobacco growth, tobacco leaf and root surface may absorb heavy metals from cultivating soil. When the tobacco leaves were manufactured into cigarette and smoked, a small amount of heavy metals may be inhaled into the human body along with the mainstream smoke.The paper is mainly consist of following studies:(1) Preparation of two porous materials, i.e. magnetic carbon nanotubes and thiol-functioned porous chitosan,(2) Establishment a solid phase extraction (SPE) method based on the synthetic magnetic carbon nanotubes as a novel adsorbent for testing the benzo[a]pyrene in edible oils successfully.(3) Examination of the adsorption efficiency of the thiol-functioned porous chitosan to heavy metals in mainstream smoke. Research details are described as follows:1. The influence of polyol reduction and coprecipitation process on the structure of Fe3O4/MWCNTs composite magnetic nanoparticles was compared. The optimal conditions of polyol reduction method were1.20g NaAc·3H2O,200℃reaction temperature and16h reaction time. Whereas, the optimal conditions of coprecipitation method were Fe3+/Fe2+=2:1, pH10～11,800r/min stirring speed and50℃reaction temperature.Characterization by fourier transformed infrared, scanning electron microscope, X-ray diffraction, surface area analyzer and thermogravimetric analyzer showed that Fe3O4magnetic particles had successfully grown on the surface of MWCNTs. The product not only possessed satisfied specific surface area but also manifested good absorption to benzo[a]pyrene. As a result, the Fe3O4/MWCNTs composite magnetic nanoparticles that made by coprecipitation method was selected and further used in the subsequent studies.2. The detection method of trace benzo[a]pyrene on the basis of magnetic carbon nanotubes adsorbent, combined with magnetic solid-phase extraction technology was established. And the study showed that when the usage of MWCNTs was3.6mg, the oscillation extraction time was10min,4mL toluene was used as eluent, the method had good linear range with R2=0.9993,95.3-100.5%recovery,1.2-2.3%RSD%and0.15μg/L of the detection limit. Satisfactory results in the analysis of commercial oils were also obtained.3. Using chitosan as raw materials, through the gelation, glutaraldehyde crosslinking reaction, L-cysteine modification process, thiol-functioned porous chitosan was prepared and evaluated by elemental analysis, fourier infrared, scanning electron microscopy (SEM), X-ray diffraction, thermogravimetric analysis and specific surface area determination. The results showed that the product had higher sulphur content, bigger specific surface area andgood thermostability. When it was added in cigarette filter, good selective adsorption ability to heavy metals in mainstream smoke was achieved.