Agar-Graphene Oxide Composite for Copper and Lead Adsorption in Batch and Fixed-Bed Systems

Abstract

This work investigated the development of graphene oxide (GO)-based bionanocomposite hydrogels for the removal of contaminants from aqueous media, motivated by the search for sustainable, high-performance adsorbents. Initially, a GO-agar composite was evaluated for the adsorption of Cu2+ and Pb2+ ions in mono and multicomponent systems through batch and fixed-bed assays. The results demonstrated that GO incorporation increased the adsorptive capacity by 3 to 13 times, with equilibrium reached within 50 min. The process was controlled by intraparticle diffusion, showing a better fit to the Freundlich (Pb2+) and Anti-Langmuir (Cu2+) models. In multicomponent systems, Pb2+ exhibited preferential adsorption due to its higher electronegativity. The material showed high reusability, with average recoveries of ~93% after four cycles. Cost analysis indicated economic viability (€ 27.40 per column); however, the manual shaping of the particles was identified as a bottleneck for scalability. To mitigate this challenge, an exploratory study employed additive manufacturing (Direct Ink Writing) to produce alginate/cellulose/GO structures. The formulations exhibited optimized rheological properties, ensuring high shape fidelity and an adsorptive capacity of ~25 mg∙g-1 for the drug chloroquine. It is concluded that the integration of bench-scale studies and 3D printing establishes a promising methodological framework that combines low cost with the automation of adsorbent geometry, indicating that GO hydrogels have the potential to evolve as scalable and versatile platforms for advanced water treatment.