Ca-alginate as a support matrix for Pb(II) biosorption with immobilized biofilm associated extracellular polymeric substances of Pseudomonas aeruginosa N6P6

•Protein like fluorophore of EPS significantly sequester Pb(II) with binding constant (Kb) of 5.67 l mol−1.•Maximum Pb(II) biosorption was observed at pH 6.•Initial Pb(II) concentration and contact time influence the biosorption efficiency of different biosorbents.•EPS-alginate biosorbent has highest capacity of Pb(II) biosorption (416.67 mg g−1).

The contribution of immobilized biofilm associated extracellular polymeric substances (EPS) of a marine bacterium Pseudomonas aeruginosa N6P6 in sequestering Pb(II) was investigated. The interaction between extracellular polymeric substances (EPS) and Pb(II) during the sorption process of Pb(II) was investigated using three-dimensional excitation-emission matrix (3D-EEM) and atomic absorption spectroscopy. 3D-EEM showed that the intensities of protein (PN) like fluorophores decreased during the Pb(II) sorption process. The interaction of Pb(II) and EPS fluorophore occurs spontaneously (ΔG = −13.79 kJ/K/mol) at 25 °C with a binding constant value of 5.67 l mol−1. Through comparison of Pb(II) sequestration on immobilized live biomass and pristine alginate beads, we found that immobilized biofilm derived EPS contribute significantly to Pb(II) sequestration. The biosorption was studied by varying pH from 3 to 8 and initial Pb(II) concentration from 100 to 600 mg l−1 to find out the optimized conditions for maximum Pb(II) removal by various biosorbents. The Pb(II) biosorption capacity of the EPS alginate beads was significantly higher (416.67 mg g−1) than that of alginate biomass beads (232.55 mg g−1) and pristine alginate beads (120.48 mg g−1) (P < 0.05; One way ANOVA and Tukey's HSD test). The maximum adsorption of Pb(II) on all the prepared biosorbents were observed at pH 6. Two equilibrium models, Langmuir and Freundlich, were used for computing the efficiency of Pb(II) binding by the developed biosorbents. The adsorption isotherms, Langmuir and the Freundlich type models were found to exhibit good fit (R2 = 0.99) to the experimental data. The reusability of the EPS alginate biosorbent was studied by Pb adsorption (68.33%) and desorption (66.8%) from contaminated water after three adsorption/desorption cycle.

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