The Preparation And Adsorption Property Of Pb²⁺-Imprinting Modified Magnetic Chitosan Nano-Material

Chitosan is a natural polymer compound, which possess non-toxicity,hydrophilicity, biocompatibility, biodegradation properties and so on. Chitosan canabsorb or chelate heavy metal ions, some protein and starch, because its molecularsurface contains a lot of free amino and hydroxyl. In recent years, chitosan as a cheapeffective adsorbent has received great attention. However, the application of chiotsanas sorbent has been limited, since the molicular contains a large number of aminowhich can easily be protonated by combining H+in water and dissolve in acidsollution.The chitosans modified with carboxyl, amino and crosslinking agent wereprepared in this paper, which improved the adsorption capability and stability ofchitosans sorbent and broaden the the scope of their application. Nanometer Fe₃O₄particles were coated by crosslinked chitosan. A rapid separation of the adsorbent fromwastewater solutions was achieved by magnetic separation technology. Furthermore,Pb²⁺imprinted magnetic chitosan nano-materials were also prepared in order toimprove the selectivity of the adsorbent for the template ion. The specific researchcontents and the results are as follows:1. Preparation and characterization of Fe₃O₄nanoparticlesMagnetic Fe₃O₄nanoparticles were prepared by chemical co-precipitation method.Morphology and size of the Fe₃O₄particles were observed by Field-emission scanningelectron microscopy （FE-SEM）. It was observed that the microstructure of Fe₃O₄isspherical and the average size of Fe₃O₄powders is about20-30nm. Crystal phaseidentification was carried out on an X-ray diffractometer （XRD）. The results show thatthe prepared Fe₃O₄is a single pure phase and belongs to the inverse spinel crystalstructure.2. Preparation and characterization of magnetic cross-linked chitosannano-materialsCarboxyl-modified Magnetic crosslinking chitosan was prepared usedα-ketoglutarate by inverse-phase suspend polymerization method. Amino-modifiedmagnetic chitosan was also prepared used glutaraldehyde and ethylenediamine.Morphology and size of the microspheres were observed by SEM. Structures andcompositions of the prepared adsorbents were characterized by fourier transfer infrared （FT-IR） spectrameter、 XRD、 differential scanning calorimetry （DSC） andthermogravinetry （TG）. The results show that the prepared adsorbents are sphericitywith uniform size and the average size is about80-90nm. Carboxyl andamino-modified chitosan were prepared successfully.3. Studies on adsorption behavior for magnetic crossing chitosan microspheresAdsorption capability for Pb²⁺of the two magnetic chitosan adsorbens（KCTS/Fe₃O₄and EMCS） was investigated. Effects of environmental factors on theiradsorption properties were also studied. The results reveal that both of the twoadsorbens are in a relatively short period of time to reach saturation adsorption andKCTS/Fe₃O₄show a greater adsorption capacity.4. Studies on preparation and adsorption behavior of Pb²⁺-imprinted magneticcross-linked chitosan nano-materialsPb²⁺-imprinted magnetic cross-linked chitosan nano-materials were prepared andtheir Adsorption capability was also investigated. The results show that the imprintingadsorbents show several advantages, such as high selectivity for the adsorption of Pb²⁺,simple regeneration conditions, good stability and high recycling rate.