Comparative kinetic study of Pb(II) and Cd(II) metal ions removal from aqueous solutions by <i>Lactobacillus helveticus</i>, <i>Limosilactobacillus fermentum</i>, and <i>Lactiplantibacillus pentosus</i>

ABSTRACT In this study, selected lactic acid bacteria, including Lactobacillus helveticus, Limosilactobacillus fermentum, and Lactiplantibacillus pentosus, were evaluated for their potential to remove Pb(II) and Cd(II) ions from aqueous solutions. The highest removal efficiency was achieved at a pH value of 4. Kinetic modeling using the pseudo-first-order, pseudo-second-order, and intraparticle diffusion models demonstrated that the intraparticle diffusion model provided the best fit for describing the adsorption process. The results of the study indicated that among the three bacteria tested, L. fermentum exhibited the highest maximum adsorption capacity for Pb(II) at 4.95 mg g−1, followed by L. helveticus at 4.91 mg g−1 and L. pentosus at 4.08 mg g−1. In contrast, for Cd(II) adsorption, L. helveticus showed the highest maximum adsorption capacity at 4.38 mg g−1, followed by L. pentosus at 3.45 mg g−1 and L. fermentum at 2.86 mg g−1. The mechanism of Pb(II) and Cd(II) ions removal by LAB strains involves adsorption onto the bacterial cell surfaces, where interactions such as ion exchange, electrostatic attraction, and complexation play crucial roles. Overall, L. helveticus, L. fermentum, and L. pentosus hold promising potential for various applications in wastewater treatment, particularly in the removal of heavy metal ions.