Nickel-doped mesoporous manganese oxides for enhanced peroxymonosulfate-based oxidation of tetracycline hydrochloride: Performance and mechanism

The modified inverse micelle approach was used to create nickel-doped mesoporous manganese oxides (Ni-MM). These novel catalysts showed much higher reactivity to activating PMS than the pristine mesoporous manganese oxides, and 5% doping ratio (Ni/Mn) would lead to best degradation efficiency in the PMS/Ni-MM system. X-ray diffraction (XRD) displayed that the crystal composition of manganese oxides would be changed and scanning electron microscope (FESEM) presented that the surface morphology was transformed from spherical deconstruction to sponge-like particles since Ni was doped into MM. Mn2+, Mn3+ and Mn4+ were coexisted in 5%Ni-MM, and Ni in the material was +2. The operating conditions such as catalyst dosage, PMS dosage, TCH concentration and beginning pH. Under the ideal reaction conditions for 5%Ni-MM/PMS system, the TCH degradation efficiency could be 86.79% in 30 min, and it could be used in the pH range (3-11). In the presence of Cl−, SO42−, CO32−, PO43−, HCO3−, humic acid (HA) and natural water bodies, TCH degradation efficiencies could still be greater than 80%. Quenching experiments indicated that O2·-, 1O2, SO4·- and ·OH contributed to TCH degradation in the 5%Ni-MM/PMS system. The intermediates were identified by LC-MS, and the pathways for 5%Ni-MM/PMS system degradation of TCH were conjectured.