Highly efficient removal of tetracycline hydrochloride under neutral conditions by visible photo-Fenton process using novel MnFe2O4/diatomite composite

A simple solvothermal method was used to prepare poly-porous MnFe2O4/diatomite (MFD) with excellent catalytic performance. The characteristics of the prepared catalysts were examined by XRD, SEM, BET, XPS, UV DRS, PL and NH3-TPD. BET analysis indicated that introduction of diatomite could increase the specific surface and porosity of the MFD. NH3-TPD studies clearly revealed that loading onto diatomite increased the availability of acid sites and surface hydroxyl groups in the composite materials. Under the combination of visible light and H2O2, the degradation effect of 80 mg/L 100 mL tetracycline hydrochloride (TC-HCl) reached 96.7% within 60 min at 0.1 g/L MFD and initial pH value, according to the experimental results. The proposed heterogeneous photo-Fenton system with MnFe2O4/diatomite showed an extremely wide pH range of 3-11 for TC-HCl degradation. At pH = 7, 91.8% of the TC-HCl (80 mg/L 100 mL) could be degraded within 60 min. In addition, the removal rate remained close to 90% after 60 min of irradiation at pH = 9 and 11. Free radical capture experiment showed that superoxide radicals (center dot O-2(-)) and holes (h(+)) play a crucial role in the removal of TC-HCl. Moreover, the synergistic activation of H2O2 by Fe and Mn was confirmed to promote the degradation, leading to higher TC-HCl removal efficiency.