Adding Value to Chitin Waste As Heavy Metal Immobilizer.

In recent times, biosorption has been extensively studied as a cost effective alternative approach to conventional environment remediation technologies. Using renewable and low-cost materials such as plant or animal waste, biosorption offers a sustainable way of waste and pollution management. Chitin waste is in abundance due to growing global consumption for seafood. Most of the seafood wastes such as shells of crab, shrimp and squid pen are rich in chitin that can be used for environmental remediation. Numerous processes to add value to chitin waste have been successful. Chitosan which is derived from waste chitin has been widely commercialised as combat bandages as well as environmentally friendly agricultural amendment. Not only that, chitosan has also been used as coagulant and adsorbent in wastewater treatment due to its extensive network of amine and hydroxyl groups. The potential of waste chitin for metal immobilization can be enhanced further with the introduction of sulfur elements, which simultaneously enhances selectivity to heavy metals as well as improving durability to acid degradation. Sorption of heavy metals such as cadmium and lead are enhanced by the high sulfide content in chemically modified chitosan. The dissolution of chitosan in acidic condition is alleviated by formation of disulfide and thiourea crosslinks. The metal uptake of modified chitosan depends on the porosity and well as the degree of conversion of modified chitosan. Porous and highly functionalised chitosan material has higher cadmium and lead uptake as compared to chitin or chitosan.