Synergistic activation of peroxymonosulfate for organic pollutants degradation with hydroxyapatite/manganese oxides hybrid catalysts.

• MnHA hybrid was prepared by deposition of HA on OMS-2. • Synergistic activation of PMS by MnHA hybrid was observed. • Interaction between OMS-2 and HA was characterized and discussed. • Detailed mechanism of MnHA+PMS system was proposed. The development of environmental friendly and efficient catalysts in advanced oxidation processes to degrade organic pollutants is highly desired. The complex metal oxides usually exhibit superior performance due to the potential synergistic effects between different metal oxides. In this study, hydroxyapatite (HA) coupled with manganese oxide OMS-2 hybrid (MnHA) was prepared and investigated as a catalyst for synergistic activation of peroxymonosulfate (PMS). The degradation of Acid Orange 7 with the hybrid was 2.94 and 10.8 times higher than those with pure OMS-2 and HA respectively. More importantly, it was found that Ca was not only coordinated with P O/P O groups in HA but also with Mn O groups on the surface of OMS-2; and then electrons were suggested to be transferred from HA to OMS-2 to decrease the Mn O Mn bond energy, leading to easier oxidation of Mn species by PMS. HO, SO 4 − , O 2 − and 1O 2 were found to be involved as reactive species in MnHA+PMS system, but 1O 2 played a more important role. The performance of the system under different conditions such as solution pH and concentrations of catalyst, pollutant and PMS was also studied. This work is expected to be helpful to design new and highly active catalysts for PMS activation. [ABSTRACT FROM AUTHOR]