Superoxide radical mediated persulfate activation by nitrogen doped bimetallic MOF (FeCo/N-MOF) for efficient tetracycline degradation

Abstract

• N-doped Fe/Co-bimetallic MOF was synthesized by “one-pot” hydrothermal method. • FeCo/N-MOF/PS oxidation achieved high TC removal (99.35%) and RSE (6.13%). • The FeCo/N-MOF had a great TC degradation over a wide range of pH. • O 2 − was the dominant radical in the FeCo/N-MOF/PS system. Metal organic frameworks (MOFs) have been widely concerned by researchers as catalytic materials. In this work, nitrogen doped Fe, Co bimetallic MOF named FeCo/N-MOF was prepared by “one-pot” hydrothermal method as a catalyst for activating persulfate to degrade tetracycline. The hexagonal spindle crystals morphology and porous structure were observed on the FeCo/N-MOF. The X-ray photoelectron spectroscopy (XPS) showed that Fe(III) and Co(II) were the main active sites and the presence of pyrrole N was positive to the catalysis. The different conditions of catalyst dosage, pH and persulfate concentration were discussed to further understand the mechanism of FeCo/N-MOF on tetracycline (TC) degradation. The results revealed that about 99% of tetracycline was degraded in 150 min when FeCo/N-MOF was 0.4 g/L and persulfate was 5 mmol/L in a wide range of pH from 3 to 9. Moreover, the reaction stoichiometric efficiency of persulfate was 6.13%. There were radicals and non-radical pathways in the process of TC degradation and the superoxide radical was the main active substances. This study suggested that FeCo/N-MOF was of great potential in persulfate activation for water purification, which also provided a platform for MOF-derived catalysts in the field of advanced oxidation.