Modified Chitosan Magnetic Adsorbents: Preparation, Characterization And Applications In Heavy Metal And Dye Adsorption

Contaminant of heavy metals and synthetic dyes in water has led to sorts of ecologicaland environmental problems. Kinds of novel magnetic adsorbents have been developed toremove heavy metals and dyes, which showed various advantages, such as highly efficient,low cost, simple, convenient, and easy to operate in industrial scale etc. Magneticadsorbents that contain natural polysaccharide chitosan and magnetic nanoparticles ownsome properties like high efficiency, cheapness, and biodegradability etc., so that they might bepotential candidates in removal of heavy metals and dyes. In this thesis, two kinds of modifiedchitosan magnetic adsorbents were designed and prepared, and their capabilities andmechanism for adsorption of toxic metal ions and cationic dyes were further investigated.Experimental methods and results are shown as follows:(1) Two kinds of novel chitosan magnetic adsorbents, EDTA modified chitosan/SiO2/Fe3O4magnetic adsorbent (abbreviated to EDCMS) and taurine modified chitosan/Fe3O4magneticadsorbent (abbreviated to TCM), were synthesized via surface modification andcharacterized by XRD, FTIR, SEM, TGA, VSM etc.(2) EDCMS showed excellent adsorption capacity for Cu(II), Cd(II) and Pb(II) ions atpH≥2. At pH5and25°C, the maximum adsorption capacities for Cu(II), Cd(II) and Pb(II)were0.699,0.596and0.563mmol g1, respectively. Besides, it exhibited good adsorptionability for two kinds of cationic dyes, i.e. crystal violet (CV) and methylene blue (MB),in dye solutions of pH higher than5. At pH7and25°C, the maximum adsorption capacitiesfor CV and MB were227.3and138.9mg g1, respectively. Also, it showed good reusabilityfor both the heavy metal ions and the cationic dyes. In addition, it was able to efficientlyremove the heavy metals in some traditional Chinese medicine extracts, such as extracts ofastragalus root, angelica and composite of astragalus root and angelica, and at the same time, the amount of the main pharmacodynamic composition in angelica extract, i.e. ferulaic acid,did not significantly changed before and after the removal of heavy metals.(3) TCM also exhibited excellent adsorption capability and reusability for MB.At pH5and9(25°C), its maximum adsorption capacities for MB were202.4and380.3mg g1, respectively.