Regeneration of chitosan-based adsorbents used in heavy metal adsorption: A review

Adsorption of heavy metal ions on chitosan-based adsorbents has been extensively investigated. However, few studies explored the feasibility of desorbing and regenerating chitosan. Adsorbents used after adsorption of heavy metals are discarded, and this practice exacerbates the solid treatment problem. Regeneration and reuse of exhausted adsorbents should be considered to operate environment-friendly and cost-effective adsorption. This review was performed to summarize the desorption of heavy metal ions and possible regeneration of chitosan-based adsorbents using various desorption agents such as acids, alkalis, salts, and chelating agents. It was found that the highest desorption efficiencies obtained by acidic eluents. The percentage use of desorption agents for desorbing followed the order of acids (49.3%) > chelators (26.9%) > alkalis (14.9%) > salts (8.9%). Moreover, the proper desorption time were estimated to be 0.84 by 1.37 h. Beneficial information is provided for regeneration and recovery of chitosan adsorbents.