Preparation And Application Of Composite Magnetic Nano Materials Based On Natural Polymer

With small radius and large surface area, the adsorption capacity of magnetic nanoparticles is larger than the non-magnetic nanoparticles, which makes the magnetic nanoparticles the ideal adsorbent due to its superparamagnetism and quick separation after adsorption of contaminants. However, its high specific surface area is apt to cause the particles agglomerate together. In order to improve its dispersion and stability for practical use and broad application fields, the surface of magnetic nanoparticles is required to be modified and coated.Based on the above analysis, this article introduces the preparation for three kinds of magnetic adsorbent materials. The first material is Fe3O4@TA-Fe3+,prepared by coated Fe3O4 with tannic acid(TA) and Fe3+ through complexation; the second material is Fe3O4/ TA?PA?Cys,which prepared by Fe3O4 coated with tannic acid and formaldehyde polymer under the condition of cysteine as stabilizer; the third material is Fe3O4@C,prepared by the Fe3O4 coated with carbon material obtained by the high temperature carbonization of dopamine coated Fe3O4 under the argon environmental protection. The three prepared materials were characterized with TEM,SEM?XRD?FTIR?VSM, etc. This article also studied the adsorption properties of the three prepared materials for methylene blue dye, methylene green and heavy metal ions Cu2+, Hg2+, Pb2+.The first part of the article studied the adsorption properties of tannic acid(TA) coated Fe3O4 new material(Fe3O4@TA-Fe3+) for Pb2+ and Hg2+. It showed the effects of pH on the adsorption and studied the adsorption isotherms and adsorption kinetics of Fe3O4@TA-Fe3+ for Pb2+ and Hg2+. The result showed the ideal adsorption effect of Fe3O4@TA-Fe3+ for Pb2+ and Hg2+ heavy metal ions in neutral environment. The kinetic study showed that the adsorption of Pb2+ and Hg2+ on Fe3O4@TA-Fe3+ fitted well with pseudo-second order kinetic equation. The adsorption data of for Pb2+ and Hg2+ were in line with Langmuir model. The adsorption capacity were 1115.2 mg·g-1 and 279.3mg·g-1 relatively. At pH 2.0, the TA-Fe3+ capsules shrank immediately and disassembled,which led to the low adsorption rate of the adsorbent Fe3O4@TA-Fe3+ for Pb2+ and Hg2+. The second adsorption assay result was not satisfactory. However, in an acidic environment, the Fe3O4 is still stable which means the Fe3O4 can be coated again by tannic acid poly for recycle.The second part showed the successful synthesis of cysteine mixed tannic acid(TA) and formaldehyde(PA) copolymer coated Fe3O4(Fe3O4/TA&PA& Cys). As a stabilizer and a hetero atom source(containing a nitrogen atom and a sulfur atom), the cysteine played a very important role in the synthesis, which enriched the nature of Fe3O4. Elemental analysis indicated the presence of cysteine in Fe3O4/TA&PA&Cys. The adsorption properties can be tested by dye methylene blue, methyl green and heavy metal ions Cu2+, Hg2+, Pb2+. The adsorption kinetics study showed Fe3O4/TA&PA&Cys adsorbing the contaminants methylene blue, methyl green, Hg2+, Cu2+, and Pb2+ comploys with the pseudo-second order kinetic equation; The adsorption isotherms of Fe3O4/TA&PA&Cys was show by the Langmuir equation, the maximum amount of adsorption of methylene blue, methyl green, Hg2+, Cu2+, Pb2+ were over 86.80, 174.8, 127.5, 83.6, 119.5 mg.g-1, which showed that the Fe3O4/TA &PA&Cys is a promising adsorbent.The third part studied carbon coated magnetic nanoparticles prepared with polydopamine as carbon precursor. The Fe3O4@C composite was obstained by the high temperature sintering of polydopamine coated Fe3O4 through Polydopamine selfpolymerization under Ar atmosphere protection. The stability and dispersion of the carbon coated Fe3O4 was increased after coating. The Fe3O4@C was characterized by scanning electron microscope, transmission electron microscope, Fourier transform infrared spectrometer and vibrating sample magnetometer. The result proved that the core-shell Fe3O4@C was successfully constructed. In order to test the adsorption ability of the composite, methyl green was selected as goal pollutants. The study showed the solution pH has a significant effect on the adsorption of methyl green, and the adsorption capacity increased significantly along with the increase of solution pH. The kinetic study showed that the adsorption of methyl green on Fe3O4@C fitted well with pseudo-second order kinetic equation, and adsorption rate was quite fast. The obtained Gibbs free energy values were negative, indicating that the adsorption of methyl green is spontaneous. Calculating from Langmuir adsorption isotherm, the maximum adsorption capacity of Fe3O4@C for methyl green from pure water, lake water, and tap water were 490.1, 442.5, and 389.1 mg·g-1, respectively.