A novel magnetic double MOF composite is synthesized for removing azole fungicides economically and efficiently

Abstract

In this study, Fe3O4@ZIF-90@MIL-68(Al) composite was synthesized by a facile method and used as a reusable adsorbent to effectively remove azole fungicides from paddy field water. Notably, the introduction of ZIF-90 made the magnetic adsorbent more stable and significantly improved the adsorption performance. Specifically, a series of characterization analysis were carried out and this composite displayed a high specific surface area, excellent magnetic strength, and good thermal stability, which meet the expectations. Additionally, the adsorption behaviors and mechanisms of Fe3O4@ZIF-90@MIL-68(Al) toward azole fungicides were studied systematically. The pseudo-second-order kinetic model and Langmuir isotherm model was confirmed to be more suitable for describing this adsorption process. Besides, the adsorption process of azole fungicides onto Fe3O4@ZIF-90@MIL-68(Al) was mainly based on pore filling, surface complexation, covalent bonding, π-π stacking effect and hydrogen bonding. Interestingly, the maximum adsorption capacity of Fe3O4@ZIF-90@MIL-68(Al) toward prochloraz was 352.32 mg g−1, which was probably one of the highest adsorption capacities reported. Meanwhile, the magnetic adsorbent can be regenerated by methanol treatment and maintain a high adsorption capacity after the 10th cycle. Hence, this work provides an economical and feasible method for removing azole fungicides from field water samples.