Removal of toxic metals from water using chitosan-based magnetic adsorbents. A review

Environmental pollution by toxic metals causes serious health complications, thus requiring advanced remediation methods for waters and effluents. In particular, chitosan-based magnetic materials have been recently developed to remove metals from aqueous solutions, industrial wastewater and water from lakes and rivers. Here, we review the adsorption of lead (Pb), cadmium (Cd), mercury (Hg) and arsenic (As) using magnetic chitosan. The manuscript presents recent experimental findings on the synthesis of magnetic adsorbents, focusing on magnetization methods, the main aspects of adsorption and adsorbent regeneration. The major findings are: (1) Kinetic patterns are mostly correlated by pseudo-second-order equations. (2) Langmuir isotherm model provides satisfactory estimations of monolayer capacity, the highest reported values being 341.7 mg/g for lead, 152 mg/g for mercury, 321.9 mg/g for cadmium and 65.5 mg/g for arsenic. (3) Most magnetic chitosan-based adsorbents keep their magnetic features and adsorption efficiency in consecutive adsorption–desorption runs. Overall, most chitosan-based magnetic adsorbents provide effective uptake of toxic metals ions from aqueous media and have a high degree of reusability.