Development of a polymeric nanocomposite as a high performance adsorbent for Pb(II) removal from water medium: Equilibrium, kinetic and antimicrobial activity

Highlights: • CSt-ZnO nanocomposite was prepared by mixing the suspension slurry of cross-linked starch and the gel of ZnO. • CSt-ZnO nanocomposite had high adsorption capacity for Pb(II) removal and good reusability. • Pb(II) was efficiently eluted using 0.1 M HCl and CSt-ZnO was effectively recycled. • The antibacterial activity of CSt-ZnO nanocomposite was studied against S. aureus and E. coli. In the present study, starch based ZnO nancomposite (CSt-ZnO) was synthesized for the efficient removal of Pb(II) ions from aqueous medium. The structure and morphology of CSt-ZnO nancomposite was characterized using SEM, FTIR, TGA, BET, XPS and zeta potential measurements. The effect of contact time, pH, temperature and initial concentration of Pb(II) on the adsorption was studied. The optimum parameters for maximum Pb(II) removal were time-120 min; pH-6; temperature-318 K and C_o–20 ppm. The maximum Langmuir adsorption capacity of CSt-ZnO nancomposite was 256.4 mg/g at 298 K. With increasing the temperature from 298 K to 318 K, the maximum adsorption quantity (q_m) was improved from 256.4 to 476 mg/g which showed the endothermic nature of Pb(II) adsorption on CSt-ZnO nanocomposite. The sorption isotherm and kinetics model fitting studies, confirmed that data fit well to Freundlich isotherm and pseudo-first-order kinetics models, respectively. Thermodynamic studies inferred a spontaneous and endothermic nature of adsorption. Moreover, the adsorption capacity was 68% even after four adsorption-desorption cycles which revealed the reusable performance of CSt-ZnO was well. The antimicrobial activity of CSt-ZnO nanocomposite was also examined against S. aureus and E. coli.