Biological Manganese Oxides (BMOs) Produced by Bacillus sp. H27: Tetracycline Removal, Mechanism of Action, and Application Potential

Abstract

The use of antibiotics not only directly promotes the production of antibiotic-resistant genes in the environment but also accelerates their spread. So, removing antibiotics from the environment is urgent. Microbial removal of antibiotic resistance has the advantages of low energy consumption, high efficiency, and safety and has become a research hotspot in the field of environmental science. In this study, the conditions for the formation of biological manganese oxides (BMOs) through the oxidation of Mn(II) by Bacillus sp. H27 were optimized, and the oxidation mechanism was elucidated. Characterization of their morphology and structure revealed BMOs’ adsorption and catalytic oxidation properties, and an efficient removal rate (90.15%) of TC (tetracycline) in water and reaction rate k was obviously improved. BMOs’ k values were 1.72 times, 13.8 times, and 35.4 times for the purified BMOs, chemical manganese oxides (CMOs), and biochar, respectively. In addition, electron paramagnetic resonance (EPR) testing combined with a quenching experiment and characterization analysis showed that Mn(III) intermediates and •O2– played important roles in the reaction. Density function theory (DFT) and liquid chromatograph–mass spectrometer (LC-MS) were used to identify 14 possible degradation products, most with reduced toxicity. BMOs have excellent catalytic stability and application potential. This study offers a new strategy for water purification.