Absorption behaviors and structure changes of chitin in alkali solution

Absorption behaviors of chitin in alkali solution under different treatment conditions of alkali concentration, soaking time, soaking temperature and added ethanol were studied. The solid state structural changes of the resulting chitin were investigated by X-ray diffraction and FT-IR spectroscopy. The results showed that the physical absorption of alkali solution occurred instantly when soaked in alkali solution, while the absorption equilibrium was established after soaking 4 h at room temperature. The absorbency increased as temperature decreased or alkali concentration increased. Maximum absorbency was achieved at freezing temperature with a 20 wt% NaOH solution. The addition of ethanol accelerated the alkali absorption of chitin. Hydrogen bonds in chitin were weakened by the alkali treatment and the crystallinity of chitin decreased significantly when soaked in higher concentration alkali solutions at room temperature. The molecular weight and degree of acetylation (DA) of chitin decreased significantly at treatment temperatures higher than 20 °C or treatment times longer than 4 h.