| Chitosan (CS) is one of partially N-deacetylated product from chitin, which consists of 2-acetamido-2-deoxy-β-glucose throughβ(1→4) linkage. It is the one and only natural alkaline polysaccharide, which has a wide application in nature. Recently, much attention has been paid to chitosan because of its rich resources, excellent properties such as biocompatibility, non-toxicity, bioactivity and physicochemical property. There is a vast of application for chitosan in chemical industry, textile, food and medicine industry. As containing hydroxyl, amino and other active groups within a molecule, it has a strong complexing ability of metal ions and can be as an adsorbent of heavy metal ions in wastewater treatment. However, because of its insoluble nature of water and the organic solvent, its application is limited. Therefore, preparing water-soluble chitosan and its derivatives to improve its solubility and functionality and widen the practice range have become an important issue on research and development of chitin and chitosan now. The chemical modification of chitosan is an effective way to improve its application performance. In this thesis, the etherification and properties of chitosan derivatives using physical field was studied to accelerate the reaction and increase the reaction yield. The main contents and results of this thesis are as follows:1. Hydroxypropyl Modification of Chitosan Assisted with Ultrasonic Technology Ultrasonic technology was used to enhance the synthesis of O-(hydroxyl isopropy1) chitosan. The effects of power densities of ultrasonic field, ultrasonic irradiation time, ratios of reactant, temperature and pH value on the reactions were studied and the structure of products was analyzed. The results show that: the reaction speed of the synthesis of O-(hydroxyl isopropy1) chitosan could be quickened by the ultrasonic-assisted technology and the dosages of epoxypropane and catalyzer could be reduced. The optimum condition is: the ratio of volumn of epoxypropane and catalyzer and the ratio of gram of chitosan is 10ml:0.8ml:1g, at the temperature 60℃-70℃, radiating with ultrasound for 3h, under a power ultrasound of 120kW. The improvement of obtain ratio and substitution degree is 13.6% and 12.9 %, respectively. A new shortcut was opened up for the derivation of chitosan. 2. Preliminary Study on Antibacterial Properties of Hydroxypropyl Chitosan Enhancing with Magnetic TreatmentMagnetic treatment technology was introduced to study the antibacterial properties of hydroxypropyl chitosans. The effects of magnetic field on the antibacterial properties and the minimum inhibitory concentration of chitosan derivatives were analyzed. The results show that: after the magnetic field treatment with an intensity of 400kA/m, the antibacterial activities of O-(hydroxyl isopropy1)chitosan (HPCS) on Staphyloccocus aureus Rosenbach is increased, the minimum inhibitory concentration is decreaseed by half; the order of their inhibition acticity on the Staphylococcus aureus Rosenbach is HPCS>CS. Furthermore, antibacterial properties could be increased with the concentration of inhibitor. The results of antibacterial properties of hydroxypropyl chitosan enhanced by magnetic treatment suggest that chitosan and chitosan derivatives treated by magnetic field can be developed as an inhibitor and the applied field of chitosan can be expanded.3. Adsorption Properties of Hydroxypropyl Chitosan Enhancing with Mangnetic Treatment The magnetic field treatment technology was introduced in the researches of adsorption properties of hydroxypropyl chitosan. The adsorption process of hydroxypropyl chitosan on the three metal ions of Cr(VI), Cu(II), Ni(II) under magnetic field was studied. The effects of magnetic field intensity, the acidity and the initial concentration of metal ion solution on the adsorption of hydroxypropyl chitosan for Cr(VI), Cu(II), Ni(II) by magnetic field were investigated. The results show that the adsorption capacity is increased with the magnetic field intensity. However, the acidity and the initial concentration of metal ion solution also have a suitable value. The study reveals that the suitable magnetic treatment has a very good effect on the adsorption properties of chitosan and its derivatives on matel ions.4. Structural Analysis and Adsorption of Crosslinked Hydroxypropyl Chitosan with Cr(VI) In order to improve the adsorption capacity of hydroxypropyl chitosan for Cr(VI), crosslinked hydroxypropyl chitosan(C-HPCS) were prepared by using glutaraldehyde as a crosslinking reagent, the study on adsorption behavior of crosslinked hydroxypropyl chitosan for Cr(VI) indicates that the adsorption capacity of crosslinked hydroxypropyl chitosan is more than HPCS markedly, and C-HPCS is an excellent adsorbent of Cr(VI), its adsorption capacity increased from 0.498mg/g to 1.387mg/g. The crosslinked hydroxypropyl chitosan saturated adsorption for Cr(VI), using NaOH as a desorption agent, the desorption rate of which is over 83%. After desorption, the adsorption capacity of crosslinked hydroxypropyl chitosan is still up to 0.85mg/g. In addition, by analyzing the crystallization and surface morphology of C-HPCS before and after adsorption for Cr(VI) using the method of XRD and SEM shows that the adsorption of C-HPCS for Cr(VI) could markedly chang the the structure of C-HPCS.
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