Efficient Photocatalytic Degradation of Tetracycline on the MnFe 2 O 4 /BGA Composite under Visible Light.

In this work, the MnFe 2 O 4 /BGA (boron-doped graphene aerogel) composite prepared via the solvothermal method is applied as a photocatalyst to the degradation of tetracycline in the presence of peroxymonosulfate. The composite's phase composition, morphology, valence state of elements, defect and pore structure were analyzed by XRD, SEM/TEM, XPS, Raman scattering and N 2 adsorption-desorption isotherms, respectively. Under the radiation of visible light, the experimental parameters, including the ratio of BGA to MnFe 2 O 4 , the dosages of MnFe 2 O 4 /BGA and PMS, and the initial pH and tetracycline concentration were optimized in line with the degradation of tetracycline. Under the optimized conditions, the degradation rate of tetracycline reached 92.15% within 60 min, whereas the degradation rate constant on MnFe 2 O 4 /BGA remained 4.1 × 10 -2 min -1 , which was 1.93 and 1.56 times of those on BGA and MnFe 2 O 4 , respectively. The largely enhanced photocatalytic activity of the MnFe 2 O 4 /BGA composite over MnFe 2 O 4 and BGA could be ascribed to the formation of type I heterojunction on the interfaces of BGA and MnFe 2 O 4 , which leads to the efficient transfer and separation of photogenerated charge carriers. Transient photocurrent response and electrochemical impedance spectroscopy tests offered solid support to this assumption. In line with the active species trapping experiments, SO 4 •- and O 2 •- radicals are confirmed to play crucial roles in the rapid and efficient degradation of tetracycline, and accordingly, a photodegradation mechanism for the degradation of tetracycline on MnFe 2 O 4 /BGA is proposed.