Defect-engineered Ni-Fe-LDH with porous flower-like architecture enables boosted advanced oxidation processes: Experimental and theoretical studies

Abstract

In this paper, oxygen vacancies (VO) enriched flower-like Ni-Fe layered double hydroxide (VO-Ni-Fe-LDH) was prepared for activating peroxymonosulfate (PMS) to remove Tetracycline hydrochloride (TC). Sufficient experimental exploration and density functional theory (DFT) calculations clearly demonstrated the 3D morphology prevented the aggregation of VO-Ni-Fe-LDH and VO alter the electronic state of the surface. Thus, VO-Ni-Fe-LDH/PMS not only showed a 4 times enhancement in the reaction rate constant in comparison to Ni-Fe-LDH/PMS, but also exhibited a stable and efficient performance in continuous flow experiment up to 4.5 h. Quenching test and EPR experiments proved that degradation of TC was dominated by singlet oxygen (1O2), rather than sulfate radicals or hydroxyl radicals found by traditional LDH catalysts. The Chemical intermediates in TC oxidation process were identified through liquid chromatography-mass spectrophotometry, and degradation paths were provided for system optimization. In application, the VO-Ni-Fe-LDH/PMS system was able to withstand the effects of the water matrix, various pH values and remove the contaminants from real hospital wastewater with efficiency. This work emphasized the significance of rational architectural design combined with defect engineering in catalyst development, which holds the potential for advanced catalysis.