Next-generation adsorbents for heavy metal removal: organic, inorganic, and hybrid materials

The rising levels of toxic metals in marine waters, exceeding permissible global safety limits, have emerged as a critical threat to both ecological stability and seafood quality. Limited metal-removal efficiency was observed in conventional methods or are economically unsustainable, time-consuming, leading to the development of cost-effective, eco-friendly biosorbent solutions. This review presents a precise yet integrative analysis of biosorbents sourced from plants, microbes, agro-residues, and hybrid organic–inorganic systems, with a focus on their quantitative metal-removal performance. Plant-based biosorbents, including Prosopis juliflora root powder and luffa peels, resulted in adsorption capacities of Pb(II) and Cd(II) with 34–49.5 mg g⁻1, which have removal efficiencies above 90%, while rapeseed and maize waste biomasses removed Hg(II) up to 94–98% with capacities around 45.5 mg g⁻1. Microbial biosorbents, such as Pseudomonas aeruginosa, showed 100% Pb(II) and 88.6% Cd(II) removal, while brown algae, like Sargassum, accumulated metals up to 30% when measured by dry weight. Hybrid and nano-engineered biosorbents enhanced the removal ability of 95% and maintained 85–90% recovery over successive regeneration cycles. The important physical parameters for efficient detoxification include pH (4–6.5), contact time (30–180 min), and biosorbent dosage (0.5–4 g L⁻1) significantly affect uptake kinetics and efficiency. These findings show the high potential of biosorbents for scalable remediation in metal-contaminated aquatic ecosystems through bioremediation. Future investigations should focus on improving regeneration efficiency, physicochemical stability, and ion-selective affinity, using hybrid and nano-engineered sorbent combinations to ensure sustained and environmentally detoxification mechanisms.