Current and potential industrial and environmental applications of chitosan and chitosan-derived nanocomposites

Chitosan, a partially deacetylated derivative of chitin, has emerged as one of the most promising sustainable biopolymers because of its biodegradability, biocompatibility, low toxicity, and versatile functional chemistry. This review critically examines the current and emerging industrial and environmental applications of chitosan and chitosan-derived nanocomposites, with particular emphasis on the relationship between molecular structure, physicochemical properties, and functional performance. The roles of degree of deacetylation, molecular weight, crystallinity, and surface functionalization in governing adsorption capacity, antimicrobial activity, film-forming ability, and chemical reactivity are discussed. Recent advances in engineered chitosan systems, including nanoparticles, hybrid nanocomposites, and chemically modified derivatives, are evaluated for applications in wastewater treatment, portable water purification, food preservation and intelligent packaging, sustainable agriculture, drug delivery, wound healing, catalysis, and energy-related technologies. Attention is given to heavy metal and dye removal, controlled-release agrochemical systems, antimicrobial packaging materials, and targeted biomedical delivery platforms. In addition, the review highlights green synthesis approaches, circular bioeconomy opportunities, commercialization prospects, and the environmental implications of large-scale deployment. By integrating recent developments reported up to 2026, this review provides a comprehensive assessment of chitosan-based materials and identifies key research gaps related to process standardization, long-term safety, techno-economic feasibility, and industrial scalability. The findings underscore the potential of chitosan and its nanocomposites as multifunctional materials for sustainable industrial development and environmental remediation.