MOF-5@Ni Derived ZnO@Ni3ZnC0.7/PMS System for Organic Matter Removal: A Thorough Understanding of the Adsorption–Degradation Process

Abstract

• ZnO@Ni 3 ZnC 0.7 was successfully synthesized as an effective adsorbent and oxidation catalyst. • Surface hydroxyl groups are the key active sites of both adsorption and degradation. • The degradation process regenerates the adsorption capacity of the catalyst. • Non-radical pathway is the main pathway of degradation in ZN-CS/PMS system. • The magnetic composite can be easily separated and the reusability was verified excellent. The heterogeneous catalytic activation of peroxymonosulfate for wastewater treatment is attracting increased research interest. Therefore, it is essential to find a sustainable, economical, and effective activated material for wastewater treatment. In this study, metal–organic frameworks (MOF)-5 was used as the precursor, and a stable and recyclable material ZnO@Ni 3 ZnC 0.7 that exhibited good adsorption and catalytic properties, was obtained by the addition of nickel and subsequent calcination. To investigate and optimize the practical application conditions, the elimination of rhodamine B (RhB) in water was selected as the model process. This study demonstrated that the degradation of organic matter in the system involved a coupling of the adsorption and degradation processes. Based on this, the mechanism of the entire process was proposed. The results of scanning electron microscopy, infrared spectrum analysis, and theoretical analysis confirmed that the van der Waals forces, electrostatic attraction, and hydrogen bonding influenced the adsorption process. Electron paramagnetic resonance analysis, masking experiments, and electrochemical tests conducted during the oxidative degradation process confirmed that the degradation mechanism of RhB included both radical and non-free radical pathways, and that the surface hydroxyl group was the key active site. The degradation of the adsorbed substrates enabled the regeneration of the active sites. The material regenerated using a simple method exhibited good efficiency for the removal of organic compounds in four-cycle tests. Moreover, this material can effectively remove a variety of organic pollutants, and can be easily recovered owing to its magnetic properties. The results demonstrated that the use of heterogeneous catalytic materials with good adsorption capacity could be an economical and beneficial strategy.