Preparation method of carboxymethyl levan and applications thereof

The invention relates to a preparation method of carboxymethyl levan, namely levan is subjected to carboxymethyl modification by adopting sodium hydroxide and chloroacetic acid as reaction system, and an organic solvent as a reaction medium. The implementation steps are as follows: weighing levan; adding the organic solvent in a reaction vessel, adding levan while stirring, and controlling the water bath temperature at 25-50 DEG C; then adding sodium hydroxide solids in batches in a mixed solution, wherein the alkalization time is 15-60 minutes; then adding a chloroacetic acid solution in which the organic solvent is dissolved; regulating the reaction temperature to be 35-80 DEG C; stirring and reacting for 1-5 hours at the water bath constant temperature when the chloroacetic acid solution is progressively increased completely; standing and precipitating a reaction product after the reaction; removing a liquid supernatant; and washing the precipitates by alcohol, thus yellowish or yellow carboxymethyl levan products are obtained through vacuum frozen drying or oven drying. According to the invention, the preparation technology is simple, the reaction condition is moderate, the degree of substitution of carboxymethyl levan is high, and the carboxymethyl levan can be applied to the field of water treatment as a novel environmentally-friendly antisludging agent.