Synthesis Of Natural Macromolecule Graft Copolymer Under Microwave Radiation And Its Application

In this thesis,with acrylamide as the monomer and cerium ammonium nitrate as the initiator,chitosan graft copolymer and starch graft copolymer were synthesized under microwave radiation and their flocculation performance in treating deinking wastewater was tested.Vanillin was grafted to chitosan under microwave radiation,followed by reduction with NaBH₄ and the adsorption effect of the reduced chitosan Schiff base to Ni²⁺,Cr⁶⁺ and Mn²⁺ was studied at 25℃.The main findings are as follows:Factors that affect graft copolymerization under microwave radiation were discussed, such as ratio of monomer to raw materials,reaction temperature,reaction time and microwave power.The optimum conditions were confirmed by orthogonal experiments:for chitosan graft copolymer the reaction time 12min,the initiator concentration 5mmol/L,the monomer to chitosan mass ratio 5:1,the reaction temperature 40℃,the best grafting ratio and grafting efficiency reached 133.6%and 42.0%respectively,and for starch graft copolymer the reaction time 20min,the reaction temperature 55℃,the monomer to starch mass ratio 2.5:1, the initiator concentration 4mmol/L,the maximum grafting ratio was 211.6%and the grafting efficiency was 74.3%.The treatment effects of chitosan graft copolymer and starch graft copolymer to deinking wastewater were examined and it was founded that the two graft copolymers both have good flocculation performance,and the former is slightly better than the latter.When the amount of chitosan graft copolymer was 8 mg/L the COD removal rate was 89.9%,and when the amount of the starch graft copolymer concentration was 16 mg/L the COD removal rate was 73.7%. The COD removal rate with chitosan graft copolymer is highest when pH is 8 and the COD removal rate with starch graft copolymer is highest when pH is 7.The absorption properties of the reduced chitosan Schiff base for Ni²⁺,Cr⁶⁺ and Mn²⁺ were tested and the experimental results indicated that the reduced chitosan Schiff base have better absorption properties and higher absorption capacity to Ni²⁺,Cr⁶⁺ and Mn²⁺ than the unreduced chitosan Schiff base and the highest absorption capacities were respectively 116.23 mg/g,47.27mg/g and 63.83 mg/g.The absorption has the obvious characteristics of Langmuir type and belongs to monolayer adsorption.In addition,the structure and performance of the products were characterized by using infrared spectroscope(FTIR),differential scanning calorimetry(DSC) and scanning electron microscope(SEM).