Dual-use of sodium alginate to prepare sodium algenate -derived carbon dots sodium algenate hydrogel composite for Pb2+ removal

The effective mitigation of the environmental impact of heavy metal remains a significant scientific challenge. In this study, a novel and environmentally friendly approach has been proposed to fabricate three-dimensional (3D) functional composite materials for Pb(II) removal. The easy-to-recycle spherical adsorbent is prepared by the dual utilization of sodium alginate (SA) as a bio-source precursor for the synthesis of carbon dots (CDs) and as a natural framework for the formation of SA hydrogel. The abundant surface-active groups on the SA hydrogel not only provide additional adsorption sites for the aggregation of heavy metal ions but can also be readily cross-linked with CDs without chemical additives, and thereby offering a 3D porous structure for chelating metal ions. The resulting HL-5CDs adsorbent demonstrates an impressive adsorption capacity of 305.21 mg·g−1 for Pb(II). The adsorption mechanism involves both chemical reaction and diffusion, leveraging the porous structure and rich oxygen groups of the material. Notably, a pot experiment revealed that the as-prepared HL-5CDs could inhibit the bioavailability of Pb(II). This study introduces a green and straightforward method for creating high-performance adsorbents, showcasing potential applications in energy, cleaning, and the remediation of wastewater pollution.