Ultrafast degradation of tetracycline by PMS activation over perfect cubic configuration MnCo2O4.5: New insights into the role of metal-oxygen bonds in PMS activation

The rapid electron transfer to accelerate the redox cycle of the multi-valent metal is the key factor to enhance PMS activation. Here, MnCo2O4.5 possessing perfect cubic configuration, was successfully synthesized by a simple hydrothermal method. Benefiting from metal-oxygen bridge bonds (Mn-O-Co) accompanied by higher electron cloud overlap of Mn-O/Co-O, the as-obtained MnCo2O4.5 exhibited excellent activation of peroxymonosulfate (PMS) for ultrafast elimination of tetracycline (TC) with high mineralization capacity by breaking the thermodynamic limitation of Mn(IV) reduction to Mn(III). Moreover, the stronger bonding ability of Mn-O/Co-O, Mn-O-Co, and asymmetric electron spin orbits between Mn 3d and Co 3d endowed the as-prepared MnCo2O4.5 with trace Mn/Co leaching and could realize decent recovery capacity by magnetic assisted separation. In addition, this catalyst exhibited good resistance to inorganic anions and natural organic matter, as well as satisfactory treatment efficiency for simulated wastewater and ultra-high inactivation efficiency for Escherichia coli. Competitive radical scavenging tests and electron spin resonance (ESR) revealed the primary role of ·O2–, 1O2 and OH in TC removal. The TC degradation pathway was proposed by intermediate analysis and theoretical calculation. This work offered a new insight for the design of highly active PMS activators to achieve efficient removal of recalcitrant pollutant.