Preparation, characterization and application in environmental protection of low-molecular-weight chitosan: a review

Chitosan is a biopolymer derived from chitin, which is the second most abundant and renewable polymer in nature after cellulose. Low-molecular-weight chitosan (LMWC) is the degradation product of chitosan through depolymerization. Compared with conventional chitosan, LMWC is considered as one of the most promising functional materials due to its characteristics of lower polymerization degree, lower viscosity, good water solubility, reactivity and degradability. This review focused on the preparation and characterization methods as well as the application in environmental remediation of LMWC. The three main methods of LMWC preparation including chemical, physical and enzymatic methods were summarized and compared in this paper. The mechanism, advantages and disadvantages of various preparation methods were also discussed. In addition, the applications of LMWC in environmental fields such as water treatment, soil remediation and air purification were briefly reviewed. With the continuous progress of science and technology and the improvement of environmental awareness, it is believed that more efficient, economical and environmentally friendly chitosan degradation methods will be developed, providing strong support for the wide application of LMWC in the field of environmental protection.