Performance evaluation and mechanism analysis of potassium permanganate used for simultaneous removal of tetracycline and Cu(II)

The coexistence of tetracycline (TTC) and Cu(II) in various water bodies has been frequently detected, but their simultaneous removal efficiency is far from satisfactory. In this study, potassium permanganate (KMnO 4 ) was utilized to remove TTC and Cu(II) simultaneously from the aqueous solution. The removal efficiency of TTC (10 μM) and Cu(II) (10 μM) was 92.8% and 78.5%, respectively, after 30 mins reaction under the condition of pH 6.0 and KMnO 4 dose at 50 μM. TTC was mainly removed by KMnO 4 oxidation and Cu(II) was removed by adsorption on MnO 2 formed in situ. Afterward, the effects of initial concentrations of TTC and Cu(II), KMnO 4 dose, solution pH, temperature, and water matrix on simultaneous removal of TTC and Cu(II) were comprehensively evaluated. The increase of KMnO 4 dose and reaction temperature is more favorable to the improved removal efficiency of TTC and Cu(II). Specifically, TTC was almost 100% removed at pH 4.0, while the highest Cu(II) removal efficiency was 84.9% obtained at pH 7.0. The removal efficiency of TTC and Cu(II) in surface water remained higher than 79% and 80%, respectively. The molecular orbital calculations supported that the complexation of TTC with Cu(II) inhibited the oxidation of TTC by KMnO 4 . X-ray photoelectron spectroscopy and X-ray diffraction confirmed that the solid product formed from the reduction of KMnO 4 was amorphous MnO 2 . Furthermore, the plausible transformation pathways of TTC were proposed based on the identified intermediates. This work provides a cost-effective approach for the simultaneous removal of TTC and Cu(II) from water. • Tetracycline and Cu(II) can be effectively co-removed by KMnO 4 treatment. • Tetracycline was mainly removed by KMnO 4 oxidation. • Cu(II) was removed by adsorption on amorphous MnO 2 formed in situ. • Complexation of tetracycline with Cu(II) inhibited tetracycline oxidation by KMnO 4 .