Encapsulation of biogenic manganese oxide and Pseudomonas putida MnB1 for removing 17 α-ethinylestradiol from aquatic environments

Abstract

In this study, we fabricated BMO-MnB1 beads by encapsulating biogenic manganese oxide (BMO) and Pseudomonas putida MnB1 into a calcium alginate hydrogel matrix and evaluated its possible use as a novel material for removing 17α-ethinylestradiol (EE2) from aqueous environments. A response surface methodology (RSM) was used to investigate the individual and interaction effects of the four independent encapsulation conditions (i.e., sodium alginate concentration, CaCl2 concentration, curing time, and bead size) on the removal efficiency of EE2 to obtain optimal encapsulation products. The effects of different experimental conditions (i.e., pH, temperature, initial EE2 concentration, and BMO-MnB1 bead concentration) on the removal of EE2 were also examined. The reusability of BMO-MnB1 beads was also studied in comparison with free BMO and P. putida MnB1 and purified BMO. The results suggested that the optimal conditions for the preparation of BMO-MnB1 beads were the sodium alginate concentration of 3%, the CaCl2 concentration of 0.2 M, the curing time of 3 h, and the bead size of 2.5 mm. Successful fabrication of BMO-MnB1 beads was confirmed via optical microscopy and field emission scanning electron microscopy analysis. Initial pH, initial EE2 concentration, bead concentration, and temperature markedly affected the EE2 removal rates by the BMO-MnB1 beads. The BMO-MnB1 beads exhibited good separation and satisfactory reusability; they could be recycled up to 14 times without obvious changes in the bead structure. This study demonstrates that encapsulation of BMO and P. putida MnB1 into alginate beads can be an excellent strategy with great efficiency and reusability, and high potential for industrial applications for EE2 removal.