An environment friendly approach for heavy metal removal from industrial wastewater using chitosan based biosorbent: A review

Industrial wastewater has imposed increasing threats due to the large concentrations of various toxic and hazardous contaminants. Amongst various processes to treat wastewater, adsorption is widely being adopted due to its simplicity, good treatment efficiency, availability of a wide range of adsorbents, cost-efficiency, etc. Chitosan, the second most abundant biopolymer is well-known due to its unique properties and versatile nature like abundance, biodegradable, low-cost, presence of adsorptive functional groups, and good reactivity. Due to these properties, it is found highly potential for the application as an adsorbent to remove heavy metal ions. The present review study focuses and analyses the suitability of chitosan as an adsorbent for heavy metal removal, modifications of chitosan like cross-linking, grafting, & magnetic chitosan, the adsorption performance of chitosan and modified chitosan towards heavy metal ions along with the factors affecting it, kinetic model fitting, thermodynamic model fitting, and the isotherm fitting. The mechanism of adsorption is discussed in detail. Usage of a few novel modifiers has been highlighted. At last, the gaps in the research and future perspectives are discussed. Throughout the review, it was verified that chitosan upon chemical modifications with different physical morphologies showed good removal efficiencies and adsorption capacities for heavy metal for the synthetic wastewater due to the amino and hydroxyl functional groups which majorly took part in adsorption. Good removal efficiencies of greater than 80% were mostly obtained, with a few having extraordinary 95-96% uptake. Finally, gaps were observed in dynamic or column-based experiments and the complex industrial wastewater treatment which requires more focus to build an industrial perspective. Thus, the commercialization of modified chitosan adsorbent is quite far.

Automated summary

Chitosan, a widely adopted adsorbent, shows great potential in removing heavy metal ions due to its unique properties and abundant functional groups. Physical and chemical modifications significantly enhance its adsorption performance, but challenges remain in dynamic experiments and complex industrial wastewater treatment, hindering the commercialization of modified chitosan adsorbents.