Synthesis Of Carboxymethyl Starch With High DS By Dry Method And Its Application Performance Research

Carboxymethyl starch (CMS) is an important kind of etherified starch and is widely applied in many areas. With the increase of its demand, the researches related to CMS have became a hot topic in recent years. Till now, CMS is produced mainly by wet method industrially. But dry method, which possesses the advantages of not involving organic solvent, simple equipments and low cost, is sometimes employed. There are also some problems occurred in dry method, its low degree of substitution and bad appearance, which restrict its application area greatly.The carboxymethyl starch with high degree of substitution and high solution viscosity was prepared via reaction of starch with sodium chloroacetate using dry method. The process consists of two steps, the alkalization reaction and the etherification. The effects of reaction temperature, reaction time, the amount of NaOH on the degree of substitution and the solution viscosity were investigated. When the ratio of starch to sodium chloroacetate is 1:1, the optimal reaction conditions were: alkalization temperature 35℃, reaction time 60 min, etherification temperature 70°C, reaction time 2.5 h, NaOH 2.5 g, addition of 1.4 mL 60% isoproply alcohol the product was prepared with good degree of substitution(DS) of 0.73 and the solution viscosity was higher than 20000 mPa.s.Microwave radiation was used as the heat source, the effects of radiation time, the amount of NaOH and solvent for this system on DS and viscosity were studied. When the ratio of starch to sodium chloroacetate is 1:1, the optimal reaction conditions were: microwave radiation time 30 min, addition of 12 mL 96% isopropyl alcohol, CMS with DS 0.7 and solution viscosity of 10000~20000 mPa.s was produced, and better appearance was presented compared with that by dry method.Mass work was done to study the solution viscosity performance of carboxymethyl starch, such as the effect of solution concentration, content of salt, pH, shear force and lay time. A deep probe into its application was drawn by this research.Crosslinked carboxymethyl starch (CCMS) was produced via crosslink and etherealize-lization process and used as adsorbent. Adsorption of cationic dyes on CCMS was thoroughly studied for CCMS which is indissolved in water. The effects of temperature, reaction time, dose of adsobents and the concentration of dye solution on the residual were studied. The adsorption equilibrium data correlated well with the Langmuir isotherm model and thermo-dynamics parameters of the adsorption were calculated. Good reusability and high desorption efficiency were proved according to the repeated adsorption/desorption cycles experiments.