Carboxylated modified products of chitosan and its application

Carboxylated modified products of chitosan and its application

The introduction of carboxyl groups in chitosan improves its water solubility and makes it completely soluble in water.

Among this type of modified chitosan, carboxymethyl chitosan is the most studied

[Preparation method] Add chitosan to a three-necked flask equipped with a stirrer and reflux condenser, and add a certain amount of isopropanol to stir to swell; Swell under mild conditions to form an alkalinization center, and then add an appropriate amount of solid chloroacetic acid to the solution several times at intervals of a few minutes each time.

[Application] Sheng sealing studied wave phase polymerization aluminum chloride , chitosan, carboxymethyl chitosan and 3 (N- carboxymethyl chitosan, N, O- carboxymethyl chitosan and O -Carboxymethyl chitosan) on the dewatering performance of sludge

(1) The influence of flocculant on sludge sedimentation performance

Table 11-2 shows the change of sludge volume with time within 30 minutes of starting to settle

Table 11-2 Changes in sedimentation volume of sludge over time

(2) Transmittance of supernatant

A certain amount of flocculant was added to the sludge, and the light transmittance of the supernatant was measured for 30 minutes after stirring.

Table 11-3 Light transmittance of sludge supernatant

It can be seen from Table 11-3 that when N-carboxymethyl chitosan flocculant is used to treat sludge, the light transmittance of the supernatant is higher.

(3) Moisture content of filter cake

The moisture content of the filter cake is related to the cost and difficulty of the further processing of the mud cake

Table 11-4 Moisture content of each filter cake

It can be seen from Table 11-4 that when N-carboxymethyl chitosan is used as a sludge dehydrating agent, the resulting mud cake has a lower moisture content, the filter cake is easy to shape, and the peeling performance is good

(4) Determination of specific resistance of sludge

Table 11-5 changes the dosage of 5 kinds of flocculants to carry out dewatering experiments on sludge to determine the specific resistance of sludge dewatering

Table 11-5 Changes in the specific resistance of sludge with the dosage of different sludge dewatering agents

It can be seen from Table 11-5 that polyaluminum chloride and chitosan can also improve the dehydration performance of sludge, but the effect is obviously worse than that of carboxymethyl chitosan, and the dosage is higher than that of carboxymethyl chitosan.

(5) Comparison of calorific value before and after sludge dewatering

The moisture content of sludge directly affects the cost and difficulty of sludge treatment.

Table 11-6 Comparison of sludge calorific value before and after dewatering with different sludge dewatering agents