The Application Of Detecting Pb²⁺、Cu²⁺ In Edible Oil With Modified Carbon Nanotubes

Carbon nanotube (CNT) is a new material of nano-carbon materials. It has been widely concerned because of its porous, large specific surface area, contaminant interactions and a number of unique physical or chemical properties. This article uses poly dopamine to modify carbon nanotubes which add new radical groups to study the adsorption properties for heavy metal ions. In this study, poly dopamine modified carbon nanotubes was used as absorbents to determine trace heavy metal in edible oil (tea oil) with atomic absorption spectrometry.The first section studied the synthesis of poly dopamine modified carbon nanotubes. Dopamine oxidation occurred in the weak alkaline environment auto polymerization adhered to the surface of carbon nanotubes. Using Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction to characterize the modified carbon nanotubes, the adsorption of heavy metal ions was detected after modification by static test compared with raw carbon nanotubes. The results showed that the new characteristic absorption peak can be observed by using Fourier transform infrared spectroscopy; scanning electron microscope could observe the reduction of carbon nanotube aggregate after modification and become more dispersed; transmission electron microscopy could observe poly dopamine on carbon nanotube surface layer after modification; X-ray diffraction showed that the tube has integrate structure and the grain becomes large; By static adsorption experiment, the modified carbon nanotubes adsorption rate was significantly higher than before the modification, it indicated poly dopamine modification can effectively enhance the heavy metal adsorption properties of carbon nanotubes.The second section of the experiment using single factor analysis examined the amount of adsorbent, adsorption time, pH, temperature and other factors which affect carbon nanotubes adsorption of heavy metal ions. The results showed that adsorption effect of modified carbon nanotubes is much better than before under the condition of room temperature,50 mg of adsorbent, pH 5-7,90 min of adsorption time. This method had a good linear relation (r2> 0.9990). The recovery rate of lead, copper were more than 95% and the relative standard deviation less than 3%. The detection limits were 0.13 μg/L and 0.16 μg/L.The kinetic parameter is accord with Pseudo-first-order and pseudo-second-order kinetic models. Thermodynamics experiments show Langmuir isotherm model was well suitable for the adsorption process. The developed method was successfully applied for rapid detection of trace amounts of heavy metal ions because of convenient operation, mild reaction conditions, non-toxic side effects and quick.The third section of research built up poly dopamine modified carbon nanotubes combine with atomic absorption spectrometry to detect lead and copper in commercial oil (tea oil).