Innovative alginate-clay shell and magnetite-gelatin core composite for multifaceted contaminant removal: Cadmium,...

In this study, a novel magnetic composite adsorbent with an alginate-chamotte clay outer layer and a gelatin-magnetite core was synthesised for effective contaminant removal from aqueous solutions. The alginate component ensures biocompatibility, chamotte clay enhances adsorption, gelatin provides mechanical strength, and magnetite enables easy recovery of the adsorbent. The composite material was characterised using Fourier-transform infrared, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy-energy-dispersive X-ray analysis, micro-computed tomography, Brunauer-Emmett-Teller analysis and dynamic mechanical analysis techniques. Response surface methodology was employed to optimise cadmium and thiabendazole adsorption. Optimal conditions for cadmium removal were achieved at pH 7 using 500 mg of adsorbent, with a 30-min contact time and a 5 mL sample volume. Additionally, thiabendazole adsorption was optimal at pH 3, with a 65-min contact time. Thermodynamic and kinetic experiments revealed that both adsorption processes were spontaneous and endothermic and followed a pseudo-second-order model. Cadmium adsorption aligned with Langmuir isotherm , while thiabendazole adsorption followed Freundlich isotherm . The adsorbent also showed high antibacterial efficiency, effectively removing both Gram-positive S. aureus and Gram-negative E. coli, with adsorption capacities of 43.86 mg g^-1 for cadmium, 5.01 mg g^-1 for thiabendazole, 2.5 × 10¹⁰ CFU g^-1 for E. coli and 6.7 × 10¹⁰ CFU g^-1 for S. aureus. These results highlight the multifunctional potential of the adsorbent for wastewater treatment.