The insight into the synergistic effect between goethite and birnessite on the degradation of tetracycline

The environmental fate of tetracycline (TC) has been documented closely related to goethite (alpha-FeOOH) or birnessite (delta-MnO2) in soil, while their synergistic effect on TC transformation remains unclear. Herein, a series of delta-MnO2@FeOOH were synthesized to investigate the interaction between alpha-FeOOH and delta-MnO2 for TC transformation. The results showed that the higher specific surface area and larger amount of surface hydroxyl content were found in delta-MnO2@FeOOH than those of the bulk alpha-FeOOH and delta-MnO2, enhancing the adsorption capacity for TC. The alpha-FeOOH introduction was conducive to the electron transfer efficiency and the increase of Mn(III) species, thus, forming more reactive oxygen species (ROSs) for the oxidation of TC. Moreover, the comparative study of the degradation of the common organic pollutants in soli over delta-MnO2@FeOOH indicated the synergistic effect of delta-MnO2 and alpha-FeOOH showed selectivity in the TC degradation. In addition, 20%delta-MnO2@FeOOH displayed highest removal percentage of 98% for TC (10.0 mg/L) and the removal performance first increased and then decreased as delta-MnO2 loading on the surface of alpha-FeOOH from 10% to 70%. This study provides a new insight into the transformation of organic pollutant under the interaction between alpha-FeOOH and delta-MnO2.