Stable Cobalt Active Site on Cobalt Bismuth Oxide Activates Peroxymonosulfate for Effective Diclofenac Mineralization and Detoxification

Heterogeneous peroxymonosulfate (PMS) activation by cobalt-based catalysts has drawn much attention due to the high-performance property of cobalt ions (Co(II/III)) to activate PMS. However, the leaching and residue of Co(II/III) in water is still a hurdle to the long-term development of cobalt-based catalysts. Here, we report cobalt bismuth oxide as a new PMS activator. When using cobalt bismuth oxide to activate PMS, 100% degradation efficiency and 82.1% mineralization rate of diclofenac (DCF) are achieved within 2 mins, which are respectively 2.6 and 4.2 times higher than those using PMS alone. Density function theory calculations further prove the ability of cobalt bismuth oxide to absorb and subsequently activate surface absorbed PMS molecules. The ·O2− species are mainly responsible for the DCF decomposition. Stable phase structure and surface Co(II)/Co(III) species determine the reusability of cobalt bismuth oxide in activating PMS. Better, except for CO2 and H2O, other 14 kinds of degradation products detected in the system if PMS + cobalt bismuth oxide also show much lower toxicity than DCF. This study reports a new cobalt-based PMS activator with high efficiency and stability, which may help to develop efficient and stable heterogeneous persulfate activators for wastewater treatment