Next-Generation Sorbents For Heavy Metal Removal: A Comprehensive Review Of Graphene, Biopolymer, And Nano- Composite Systems

Heavy metal ion contamination in aquatic systems remains one of the most urgent global environmental challenges, demanding advanced, selective, and sustainable separation technologies. In recent years, rapid progress in materials science has driven the emergence of novel-generation sorbents engineered from graphene-based structures, biopolymer-derived materials, and multifunctional nano-composite systems. This review provides a comprehensive assessment of scientific development trends across these three major sorbent platforms, evaluating their structural characteristics, synthesis methodologies, adsorption mechanisms, and comparative performance. Graphene oxide and its functionalized derivatives demonstrate exceptional adsorption efficiencies due to high surface area, abundant oxygen-containing functional groups, and tunable electronic properties. Biopolymer-based sorbents, particularly chitosan, alginate, cellulose, and silk fibroin, offer biodegradable and cost-effective alternatives with strong chelating capabilities and promising regeneration behavior. Nano-composite architectures—such as zeolite–metal oxide hybrids, MOF/ZIF-based systems, COF materials, and hierarchical porous polymers—exhibit powerful synergistic effects, enabling unprecedented adsorption capacities exceeding 900 mg g⁻¹ for certain metal ions. Mechanistic analysis highlights the interplay of chelation, electrostatic attraction, hydrogen bonding, π–π interactions, and intraparticle diffusion in governing adsorption performance. Comparative evaluation reveals that while graphene-based materials excel in kinetics and selectivity, biopolymers offer sustainability advantages, and nano-composites achieve the highest overall adsorption capacities and operational robustness. Emerging trends indicate a shift toward multifunctional integrated systems, computationally guided material design, and field-scale validation to enhance industrial applicability. This review concludes that next-generation sorbents hold transformative potential for efficient, economical, and environmentally responsible metal ion separation, supporting global water purification and resource recovery efforts.