Neutralization of the residual Alkaline solution of chitosan with CO 2 gas

Abstract

Chitin is converted into chitosan by deacetylation in concentrated sodium hydroxide. Therefore, there is residual lye attached to the surface of chitosan that should be neutralized. In this study, CO2 was used to neutralize the residual alkali under different pressures, instead of washing with water. The results demonstrated that the neutralization of NaOH residue with CO 2 for the process of deacetylation of chitin is advantageous over the water-washing method. It only took 1 h to neutralize NaOH under 4 MPa and 100 rpm/min, which saved much time compared with 5 h of the water-washing method. In addition, the consumption of water was one fifth that of water-washing method, thus it could save about 80 % of water. Loss rate of chitosan after neutralization was less than half of washing. On the whole, it reduced the consumption of time, manpower, water resource, and cost. It was easy and simple to handle and facilitated the large-scale production. © Springer-Verlag Berlin Heidelberg 2014.