Chitin/Graphene Oxide Composite Materials for Heavy-Metal-Ion Adsorption.

Rare earth elements (REEs) are vital for modern technology owing to their unique properties and widespread industrial applications. However, their growing use results in increased environmental releases, raising concerns about potential ecological impacts and human health risks. The same is true for actinides like uranium. Efficient removal of these elements from water, particularly in the mining and nuclear industry, is thus crucial. Recycling these elements has emerged as a sustainable approach for wastewater processing and waste reuse. Adsorption presents advantageous properties for effective contaminant removal. The present study focuses on the synthesis and characterization of composite adsorbent materials for this application. Chitin is an abundant biopolymer with particularly promising properties, including widespread availability, low cost, biocompatibility, and biodegradability. However, the processing of chitin into stable materials is challenging due to its very low solubility. Previously, we reported the cross-linking of α-chitin with its monomer by processing in the ionic liquid (IL) 1-butyl-3-methylimidazolium acetate. These composites, however, exhibit a lower adsorption capacity than pure chitin powder due to partial blocking of adsorption sites. To overcome this problem, we have now incorporated graphene oxide (GO) into the chitin-based composite. With its large surface area and various functional groups, GO further enhances the inherent properties of chitin. These composites are shown to very efficiently remove even spurious amounts of europium and uranium from aqueous solutions.