Interaction of colloidal silver nanoparticles (SNPs) with exopolysaccharides (EPS) and its adsorption isotherms and kinetics

The adsorption of exopolysaccharides (EPS) on silver nanoparticles (SNPs) was influenced by pH, salt concentration, and zeta potential. In this paper, SNPs were stabilized using exopolysaccharides (EPS) produced by Aeromonas punctata as the capping agent. The effects of EPS concentration on the adsorption was studied by UV–visible absorption spectra. During interaction, a decrease in absorbance at plasmon peak of SNPs (425 nm) was observed till 50 mg/L of EPS, beyond that a blue shift towards 411 nm was observed. The capping of SNPs by EPS was confirmed by Fourier Transform Infrared Spectroscopy. The adsorption of EPS on nanoparticles was found to be strongly dependent on zeta potential. The equilibrium adsorption data fitted well by Langmuir isotherm compared to Freundlich curve. The kinetics of adsorption was fitted by pseudo-second-order. Desorption of EPS from SNPs was observed at alkaline pH 12. The stabilized silver nanoparticles could be more amenable towards applications in biotechnology and bioengineering.

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► Adsorption process varies with pH and salt concentration of the interaction medium.
► Adsorption process was strongly influenced by zeta potential.
► Zeta potential varies with pH and salt concentrations.
► Adsorption equilibrium isotherms fitted well by the Langmuir model.
► Kinetics of adsorption fitted by pseudo-second-order.