Studies On Preparation And Flocculation Performance Of Quaternary Ammonium Salt Of Carboxymethyl Chitosan

In this thesis,using the Chitosan for raw material and 3-chloro-2-hydroxypropyl trimethyl ammonium chloride （CTA） for the modification reagents, the quaternary ammonium salt of chitosan had been prepared in isopropyl alcohol - water-phase medium; and on this basis, using chloroacetic acid （ClCH₂COOH） as modifier, carboxymethyl chitosan quaternary ammonium salt （CM-CTACTS） had been prepared .And the chitosan derivates were used to treate the Starch juice.When the quaternization of the chitosan was being done,the synthetic condition of quaternary ammonium chitosan was optimized.The optimum condition for synthesizing the CTA-CTS was as follows:molar ratio of Sodium hydroxide to 3 - chloro -2 - hydroxypropyl trimethyl ammonium chloride was 1.1:1,3 - chloro -2 - hydroxypropyl trimethyl ammonium chloride to chitosan was 5:1,reaction temperature was 75℃,reaction time was 8h.The product was Light yellow powder, It can dissolve in water and its DS（degree of substitution）approached to 79%.The product was also characterized by FTIR and X-ray diffraction.The results of FTIR and X-ray analysis had showed that the quaternary ammonium chitosan were synthesized.Using the chloroacetic acid （ClCH₂COOH） as the carboxymethylation reagent, the quaternary ammonium salt of carboxymethyl chitosan （CM-CTACTS）was prepared. The optimum conditions for the carboxylation of CTA-CTS were as follows:molar ratio of Sodium hydroxide to CTS-CTA was 3.5:1 ,molar ratio of chloroacetic acid to CTS-CTA was 2.5:1, alkalization time was 35min, the temperature for the etherification was 70℃, etherification time was 6h. The product was Light yellow powder. It can dissolve in water and its DS（degree of substitution）approached to 83%. The product was characterized by IR and X-ray. The results indicate it to be an amphoteric derivative of chitosan. And its pH stability, water solubility of the quaternary ammonium salt of carboxymethyl chitosan were better than quarternized chitosan.The flocculation efficiency of CM-CTACTS obviously exceed that of CTA-CTS on Starch wastewater.The factors effect of flocculation capacity is such as flocculating dosage、pH ect.The result shows that the optimized flocculation efficiency condition as follows:pH=8,flocculanting dosage is 50mg/L, its max COD_cr removal ratio is 85%;when the pH=8, flocculanting dosage is 100mg/L, Settling time is 60min, its turbidity removal ratio is 96.6%.