Effective removal of lead (II) using chitosan and microbial adsorbents: Response surface methodology (RSM)

Abstract

The ability of chitosan (1% w/v), Bifidobacterium longum (108 CFU mL‐1) and Saccharomyces cerevisiae (108 CFU mL‐1) separately or in combination (chitosan/B. longum, chitosan/S. cerevisiae, B. longum/S. cerevisiae) was assessed for lead (II) removal from aqueous solutions. The results showed chitosan/B. longum adsorbent had higher adsorption percentage in comparison with other adsorbents (p < 0.05). It was selected as the most efficient adsorbent and the effect of process variables including initial metal concentration (0.01–5 mg L−1), contact time (5–180 min), temperature (4–37 °C) and pH (3–6) on the its removal efficiency was evaluated with a Box–Behnken design. Twenty-seven test runs were performed and the optimal conditions for metal adsorption was observed at metal concentration of 2.5 mg L−1, contact time of 180 min, temperature of 37 °C and pH 4.5. The maximum lead (II) adsorption yield under optimal conditions was 97.6%. The foreign ions didn't diminish lead (II) adsorption by chitosan/B. longum and it had high selectivity toward the lead (II). Adsorption behavior was analyzed using the Freundlich and the Langmuir isotherms. The correlation coefficients (R2) demonstrated the Langmuir model had a better description on metal adsorption process. Overall, isotherms revealed chemisorption and physisorption were probably involved in metal adsorption on adsorbent.