Surface Complexation Enhanced Adsorption of Tetracycline by ALK-MXene

The removal of tetracycline antibiotics from wastewater is currently an important environmental issue due to the serious water environment pollution caused by tetracycline. However, the complex composition of industrial wastewater, including a wide variety of metal ions, may affect the removal efficiency of tetracycline. In this paper, ALK-MXene with a hydroxyl-rich surface was prepared using an alkaline intercalation method to remove tetracycline from wastewater. The effects of the presence of metal ions, including Co(II), Cu(II), Cr(III), Cd(II), and Ni(II), on the adsorption of tetracycline by ALK-MXene were explored. Batch adsorption experiments showed that the presence of metal ions could improve the tetracycline adsorption capacity and that the removal capacity could be increased by 750% when coexisting with Ni(II). Three adsorption isotherm models, including the Langmuir model, Freundlich model, and monolayer model, were used to investigate the adsorption mechanism, and the results indicated that the adsorption follows the Freundlich model. Finally, systematic characterizations confirmed that adsorption occurred at the hydroxyl site on the surface of ALK-MXene, and the enhancement of surface complexation due to the surface modification of metal ions was the main mechanism for the increase in tetracycline adsorption.