Enhancing the solubility of α-chitin in NaOH/urea aqueous solution by synergistic pretreatment of mechanical activation and metal salt

Chitin is difficult to be dissolved due to its dense structure, high crystallinity, and acetyl groups. Amorphization is conducive to enhancing the solubility of chitin. In this study, an effective mechanical activation-metal salt (MAMS) technology was used to pretreat α-chitin to improve its solubility in NaOH/urea solution. The chlorides of Fe and Al showed better synergistic effect with MA, especially FeCl 3 . The crystallization index of MA-FeCl 3 -pretreated chitin (MAFCCT) decreased to 4%, attributing to that Fe 3+ and Cl - jointly disrupted the intra- and intermolecular-hydrogen bonds in chitin. In addition, during the dissolution of MAFCCT, Fe 3+ fixed on chitin could form Fe(OH) 3 colloid with OH – to induce NaOH enter the interior of chitin molecules. The solubility of MAFCCT in NaOH/urea solution at −16 °C for 8 h reached 97.1%. MAMS pretreatment is a practical technology to enhance the solubility of chitin by destroying its stable crystal structure.