Animal sourced biopolymer for mitigating xenobiotics and hazardous materials

Over the past several decades, xenobiotic chemicals have badly affected the environment including human health, ecosystem and environment. Animal-sourced biopolymers have been employed for the removal of heavy metals and organic dyes from the contaminated soil and waste waters. Animal-sourced biopolymers are biocompatible, cost-effective, eco-friendly, and sustainable in nature which make them a favorable choice for the mitigation of xenobiotic and hazardous compounds. Chitin/chitosan, collagen, gelatin, keratin, and silk fibroin-based biopolymers are the most commonly used biopolymers. This chapter reviews the current challenge faced in applying these animal-based biopolymers in eliminating/neutralizing various recalcitrant chemicals and dyes from the environment. This chapter ends with the discussion on the recent advancements and future development in the employability of these biopolymers in such environmental applications.

Reversible Metal Ion/Complex Binding to Chitin Controlled by Ligand, Redox, and Photochemical Reactions and Active Movement of Chitin on Aquatic Arthropods

There is strong adsorption of metal ions and their complexes to chitin, which depends on both the oxidation and complexation states of many of the said elements (whereas others display chemical reactions detectable via electrochemical methods while being retained by chitin); thus, ad- and desorption at ambient water concentrations (often in the nMol/L range) are controlled by the presence and photochemical properties (concerning Eu and probably U and Ag) of mainly biogenic organic matter (both DOC and POC, and DON). With chitin forming the outer hull of mobile organisms (animals), this biopolymer is expected to take part in metal distribution in aquatic (limnetic and riverine) ecosystems. Having studied the attachment of many different elements to both crayfish and grafted (marine shrimp) chitin, with the highest accumulations observed in Bi, V, Ni, and LREEs, one should consider secondary biochemical transformations which take place at different water and sediment levels. After chitin had been embedded into sediment, methanogenesis (which requires Ni), Bi, and Sb biomethylations and photodesorption in the illuminated water column will occur if there are appropriate organics, causing the vertical separation of Eu from other REEs, at least during the daytime. Eutrophication will enhance both the production and especially the photooxidation rates of organics in water because phosphorylated sugars and lipids are formed quantitatively within min P, which enter water and undergo Eu-mediated photooxidation much more readily. Another biopolymer, gelatin, acts as an inert matrix-enhancing organic photooxidation product via Eu, producing chemical waves, indicating autocatalysis upon light impact. From the redox-related photodesorption of metal analytes from chitin, both sensors and devices for (light-assisted) electrochemical energy conversion are being developed by our workgroup. The electrochemical determination of adsorption thermodynamics on chitin is thus directly linked to its applications in environmental monitoring and technology.