Sustainable Magnetically Responsive Gelatin Hydrogels with Spirulina platensis Extract for Efficient Removal of Aqueous Contaminants

Introduction: Gelatin-based hydrogels are widely used for wastewater treatment due to their biocompatibility and network-forming ability. Their adsorption performance can be enhanced by incorporating a protein-rich extract from Spirulina platensis (PC), which provides functional groups capable of chelating metal ions and interacting with organic molecules. In this work, magnetically responsive hydrogels composed of bovine gelatin, PC, and magnetite nanoparticles (MNP), crosslinked with oxidized sodium alginate (OA) and plasticized with glycerol, were developed for selective aqueous contaminant removal. Methods: The hydrogels were synthesized and characterized by FTIR, SEM-EDS, XRD, VSM, DSC, and uniaxial compression to assess structural, thermal, and mechanical properties. Crosslinking degree, total soluble material, and swelling capacity were also determined. Adsorption experiments were performed using Pb(II) ions and model dyes, with kinetic data analyzed using pseudo-first- and pseudo-second-order models. Results and Discussion: Incorporation of PC enhanced hydrogel thermal stability without significantly affecting crosslinking. Under the tested conditions, PC-containing hydrogels demonstrated markedly higher adsorption capacities for cationic species such as methylene blue and Pb(II), compared to the anionic dye eosin (i.e., 1.78 ± 0.16, 1.86 ± 0.19, and 0.41 ± 0.03 mg/g, respectively), suggesting preferential electrostatic interactions and selective affinity. Kinetic analyses, supported by FTIR, indicated that chemisorption governed the uptake of cationic species, while eosin adsorption was mainly driven by physical interactions associated with swelling. Magnetic measurements confirmed superparamagnetic behavior, enabling easy recovery of the hydrogels. discussion: The discussion was included within the results section. Conclusion: Sustainable, magnetically responsive gelatin-based hydrogels incorporating PC and MNP, crosslinked with OA, were successfully synthesized as selective and reusable adsorbents for advanced wastewater treatment.