Chitosan-based beads as sustainable adsorbents for wastewater remediation: a review

Water contamination is increasing worldwide, yet actual methods of water and wastewater treatment are limited, in particular by actual fossil-fuel derived nano-adsorbents that are difficult to regenerate. This calls for advanced methods that use sustainable materials such as chitosan. Chitosan is a biopolymer extracted from the outer skeleton of shellfish, including crab, lobster, and shrimp. Chitosan is non-toxic, abundant, and chemical and physical stable. Moreover, chitosan can be shaped into beads, sheets, membranes, and composites. Here, we review chitosan-based beads for wastewater treatment with focus on adsorption mechanisms, removal of pollutants, functionalization, metal organic frameworks, magnetic beads, imprinted and co-polymeric beads, and regeneration. We found that chitosan/Fe-hydroxyapatite beads exhibit an adsorption capacity of 1385 mg/g for the removal of lead. Imprinted magnetic chitosan beads display a reusability of 15 cycles for nickel removal.