Study On Preparation Characterization And Application Of Synergetic Oxidation Of Oligochitosan.

Chitosan is natural polymers which is rich in content.It possesses many good properties,which are antibacterial property,absorbability,non-toxicity,non-irritating and cheap,so it has been applied widely.But chitosan’s application is stilled limited by its larger molecular weight and insolubility in water,so how to prepare oligo-chitosan has become research hotspots of chitosan.Industrial-grade chitosan was used as research raw material.The oligo-chitosan was prepared through chemical method and degraded by the synergistic oxidation system.The effects of reaction time,reaction temperature,ratio of n（H₂O₂）/n（chitosan）,peroxide concentration and sodium hypochlorite concentration on the degradation reaction were studied by five groups of single factor experiments,and the optimal experimental conditions were obtained.A set of L₁₆（4⁵）orthogonal tests was designed based on the results of single factor experiments,to study the influence of different factors on the various indicators of the preparation of oligo-chitosan and optimize three optimization schemes for different indicators,and the optimal solution for preparing oligo-chitosan has been achieved by comprehensive analysis of various indicators.The characteristics of self-made oligo-chitosan and chitosan were analyzed by FT-IR,XRD and SEM.Fe²⁺adsorption experiment was studied by using self-made oligo-chitosan,and the influence of three different factors on the adsorption capacity was discussed,which were concerned the reaction time,reaction temperature and the concentration of oligo-chitosan.The main conclusions include:the optimal reaction conditions for degrading chitosan with NaClO-H₂O₂ synergistic oxidation system were achieved in the single factor experiment,reaction time was 3 h,reaction temperature was 80℃,ratio of n（H₂O₂）/n（chitosan）was 3,peroxide concentration was 10%and sodium hypochlorite concentration was 0.5%.The optimal experimental scheme was obtained by analyzing the results of orthogonal tests and the comprehensive scheme,reaction time was 3 h,reaction temperature was 80℃,ratio of n（H₂O₂）/n（chitosan）was 3,peroxide concentration was 8%and sodium hypochlorite concentration was 0.2%.The molecule structure of the self-made oligo-chitosan was almost the same as the molecule structure of the original chitosan by FT-IR,which retained the original physical and chemical properties of the origin.By analyzing the XRD curve,the crystallinity of the self-made sample was reduced,the molecular chain was smaller,and the molecular weight was reduced.The self-made oligo-chitosan was a network structure by analyzing SEM image,which was conduce to improve the self-made sample reaction capacity and adsorption performance.The results of Fe²⁺adsorption experiment using self-made oligo-chitosan showed that when the reaction time was 35 min,the reaction temperature was 30℃,and oligo-chitosan concentration was 1.5 g/L,95.22%the flocculating and adsorption rate of the oligo-chitosan are available.