Polydopamine-modified bimetallic metal organic frameworks (MOFs) for peroxymonosulfate activation to efficient degradation of tetracycline hydrochloride in wastewater

In this study, polydopamine (PDA) modified bimetallic MOFs (PDA@CoNi-MOF) catalyst was successfully prepared for the activation of peroxymonosulfate (PMS) for tetracycline hydrochloride (TCH) removal. It was found that the PDA modified MOFs had better performance and significantly improved the elimination efficiency of TCH (99.2%) compared with CoNi-MOFs. The properties of composite catalyst were fully characterized by different methods. The experimental results showed that the PDA not only enhanced the electron transfer, but also further promoted the redox cycle of metal ions, and thus promoted the production of active species. The primary active species were proven to be singlet oxygen (1O2), superoxide radicals (O2•-), sulfate radical (SO4•-) and hydroxyl radicals (•OH) in the elimination process of TCH by radical trapping tests and electron paramagnetic resonance (EPR) analyses. A possible catalytic mechanism of PMS activation by PDA@CoNi-MOF was proposed, which mainly involves the enhanced Ni3+/Ni2+ and Co3+/Co2+ cycle by PDA donated electrons. Owing to its simple preparation and excellent catalytic performance, PDA@CoNi-MOF has a broad application prospect in the treatment of refractory organic wastewater.