Heavy metal ion pollution in aquatic environments is a critical global issue, damaging ecosystems and threatening human health via bioaccumulation in the food chain. Despite promising progress with biosorbents, the development of environmentally friendly and stable heavy metal adsorbents requires further exploration. In this study, we present an algae-loaded alginate hydrogel as a composite adsorbent for heavy metals. The incorporation of algae enhanced the hydrogel’s adsorption capacity by 38.0%, 20.6%, and 27.1% for Cu²⁺, Cr³⁺, and Co²⁺, respectively. Additionally, the composite hydrogel demonstrated excellent stability and recyclability after adsorption, reducing the ecological risks associated with algae biomass usage. This algae-loaded alginate hydrogel offers an efficient and eco-friendly strategy for removing heavy metal ions from aquatic systems, highlighting its potential for environmental remediation applications.

Heavy metal pollution remains a global environmental challenge, calling for sustainable and low-cost sorbents. Here, we upcycle coir fiber into a bioinspired adsorbent by depositing a polydopamine (PDA) coating (PDA/Coir fiber) for efficient Cu(II) and Cd(II) removal from water while improving effluent safety. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric analysis (TGA) confirm successful PDA functionalization and associated structural changes. Compared with pristine coir fiber, PDA/Coir fiber shows 6.84-fold and 12.86-fold higher adsorption capacities for Cu(II) and Cd(II), respectively. Adsorption is well described by the Langmuir isotherm, indicating monolayer-dominated binding. Kinetic analysis shows that the adsorption of both ions follows the pseudo-second-order model. The fiber also exhibits good reusability over four adsorption–desorption cycles. Importantly, cytotoxicity assays of the treated solutions show substantially reduced biotoxicity after metal removal. Overall, PDA/Coir fiber offers a sustainable and low-cost platform for heavy metal removal by integrating efficient adsorption capabilities and safety implications.