Enhanced adsorption of heavy metals with biogenic manganese oxide immobilized on zeolite

Although nano-sized Biogenic Manganese Oxide (BMO) provides excellent adsorption capacity, its use in water treatment has been limited because it is too small to be readily separated from treated water. Therefore, this work investigated the feasibility of immobilizing BMO on zeolite (BMO/Zeolite) and the use of this material for heavy metal adsorption. BMO/Zeolite was prepared by incubating Pseudomonas putida strain MnB1 in the presence of Mn 2+ and natural zeolite pretreated with NaCl (NaCl-Zeolite). BMO immobilization was confirmed by transmission electron microscopy and energy dispersive X-ray analysis. The maximum BMO loading (BMO/Zeolite) was 17.09 mg/g, and the specific surface area increased as the BMO loading was increased. Isotherms and kinetics studies were performed to evaluate the heavy metal adsorption characteristics. The maximum adsorption capacities of Pb 2+ , Cd 2+ , and Zn 2+ with the BMO/Zeolite were 36.4-70.5% higher than with the NaCl-Zeolite. The amount of heavy metal adsorption increased with higher pH and temperature and with lower ionic strength. The results from this study demonstrate that immobilized BMO not only promotes heavy metal adsorption.