Glycine-modified chitosan-embedded silver nanoparticles: a green approach to Pb2+ adsorption and bioactivity enhancement

Abstract

Glycine-modified chitosan anchored silver nanoparticles (SCG) were synthesized using a green method without a cross-linking agent. UV–Vis, FTIR, XRD, TEM and SEM techniques confirmed the formation of the SCG nanocomposite and silver nanoparticles. The SCG nanoparticles, estimated at 20 nm, are smaller than the chitosan stabilized Ag (SC) nanoparticles. The biological significance of the SCG nanoparticles was assessed through their anti-oxidant and antibacterial activities. SCG nanoparticles demonstrated significant anti-oxidant activity with an IC50 of 133 µg ml⁻¹, surpassing that of SC nanoparticles. The ZoI of was found to be 30 mm for the S. aureus and E. coli bacterial strains indicating excellent antimicrobial activity. The efficiency of SCG nanoparticles in removing Pb²⁺ ions was tested using a batch adsorption process. A Central Composite Design (CCD) was employed to optimize the independent variables, and ANOVA results indicated the CCD model’s reliability and significance with a p-value < 0.0001. The SCG nanoparticles exhibited a high Pb²⁺ ion loading capacity of 270.2 mg g⁻¹ from aqueous solution with a removal efficiency of 93%. Isotherm and kinetic investigations of the equilibrium data suggest the suitability of Langmuir and pseudo-second-order kinetic models. Thermodynamic studies revealed the process’s spontaneity and exothermic nature. The mechanism of adsorption was found to be ion exchange with a mean potential energy (E_s) of 9.4 kJ/mol. These findings suggest that glycine-modified chitosan anchored silver nanoparticles have promising applications in biological and environmental domains.