Facet-dependent tetracycline transformation induced by MnO₂

It is critical to understand the environmental geochemical transformation of antibiotics and the consequential ecotoxicity. The ubiquitous co-existent minerals would promote the antibiotics' environmental transformation, however, the effect of minerals' facet exposures has not been fully revealed. In this study, we reported facetdependent tetracycline (TC) transformation induced by MnO2, as 82.35 % TC was transformed on MnO2 ' s (1 0 0) facet while only 55.58 % TC was transformed by (1 1 0) facet in 120 min. Besides Mn (IV)/Mn (III) driven one-electron oxidation, the formation of oxygen vacancies (OVs) on MnO2 would adsorb O-2 to generate reactive oxygen species (ROS) for TC's transformation. OVs-abundant (1 0 0) facet favors O2 adsorption and could activate O-2 into O-2(-) and O-1(2), resulting in a two-time faster transformation kinetic rate than (1 1 0) facet. The TC's transformation products exhibited higher acute toxicity and bioaccumulation potential, and the increased release of Mn also poses public health risks. We have provided new insights on the environmental geochemical transformation and fate of antibiotics, addressing the overlooked ecotoxicological risks.