Biosorption of Cd+2 and Pb+2 by Exopolysaccharide Extracted from Lactobacillus fermentum 6b; Adsorption Isotherm and Kinetic Studies

Abstract

Background: In recent years, the biosorption of heavy metals by Lactobacillus strains has received attention from researchers. We aimed to remove of heavy metals lead and cadmium from L. fermentum 6b exopolysaccharide in 2021.
 Methods: Extracellular exopolysaccharide was first extracted from selected probiotic strain, and then the effect of variables such as pH, the extracted exopolysaccharide adsorbent dose, contact time, heavy metal concentration, and temperature on the adsorption rate was investigated. The adsorption isotherms of Langmuir and Freundlich were also examined. Pseudo-first and pseudo-second-order kinetics equations were also investigated for the desired surface adsorption.
 Results: The adsorption process at pH=6.5, contact time=80 min, pollutant concentration=100 mg.L-1, adsorbent dose (extracted exopolysaccharide) =1500 mg.L-1, temperature=35°C for cadmium; pH= 6, contact time=60 min, contaminant concentration of 100 mg.L-1, adsorbent dose (extracted exopolysaccharide) =1500 mg.L-1 temperature=of 35 °C for lead had optimum condition. The adsorption process corresponded to Freundlich isotherm with R2=0.958 and R2=0.988, and pseudo-second-order kinetic with R2=0.99 and R2=0.85 for cadmium and lead, respectively.
 Conclusion: The exopolysaccharide extracted from L. fermentum 6b isolate can have an acceptable removal potential for lead and cadmium heavy metals.