MOF-on-MOF composite material derived from ZIF-67 precursor activated by peroxymonosulfate for the removal of metronidazole

Abstract

The removal of antibiotics, commonly detected in drinking water, as well as groundwater and surface water, poses a formidable challenge and represents a significant risk to aquatic ecosystems. To effectively eliminate these contaminants, it is essential to establish robust protocols for an efficient wastewater purification system. In this study, we successfully synthesize CoFe PBA in situ using ZIF-67 (Co) as a precursor, leading to the formation of ZIF-67/Co-Fe PBA composites characterized by a MOF-on-MOF structure. We investigate how various reaction parameters, inorganic ions, and organic matter impact the degradation efficiency of metronidazole (MNZ). The composite demonstrates exceptional adsorption capacity for MNZ, achieving 98 % degradation within four minutes—comparable to most adsorbents reported in previous studies. Both the Langmuir isotherm model and the pseudo-second-order kinetic model accurately describe the adsorption process. Thermodynamic analyses suggest that adsorption occurs through a spontaneous mechanism that absorbs heat. Furthermore, we propose a potential mechanism for adsorption. Our findings reveal that both MNZ and its intermediates exhibit significantly reduced levels of acute toxicity, developmental toxicity, and mutagenicity; thus, indicating that utilizing this composite would not result in notable secondary contamination. These investigations highlight the promise of MOF-on-MOF composites as highly effective and environmentally friendly solutions for practical wastewater treatment applications.