Role of chitosan-based hydrogels in pollutants adsorption and freshwater harvesting: A critical review

The shortage of freshwater resources is an urgent problem worldwide, especially for some areas that lack rainfall conditions. The development of reliable wastewater treatment and freshwater harvesting equipment has become an urgent demand. Hydrogel is a porous 3D network structure with good pollutant adsorption capacity, water holding capacity, water adsorption capacity, and reversible swelling ability, which has been widely used in water treatment. Chitosan (CH), as the abundant bioactive material in nature, is commonly used to prepare hydrogels with low-cost, favorable stability, good antimicrobial activity, high mechanical properties, biodegradability, and environmental friendliness. Therefore, this review presents a comprehensive review of the various applications of CH-based hydrogels in water treatment including various pollutant adsorption, oil-water separation, seawater desalination, and atmospheric condensation. The relevant mechanisms, application potential, and challenge are also illustrated. This review aims to provide a viable idea to address the shortage of freshwater resources.