Levofloxacin removal by 2D-Vermiculite loaded with NiCo2O4 activated peroxymonosulfate: Performance and mechanism

Abstract

The presence of antibiotics in wastewater threatens the human living environment. Activated peroxymonosulfate (PMS) method is often used for catalytic degradation of antibiotics. However, how to reduce catalyst cost and ensure efficient degradation of antibiotics at the same time is a sticky issue for the activated PMS method. Two-dimensional vermiculite flakes (2D-VMT) is cost-effective and can be used as catalyst carriers for PMS activation. Hence, we exfoliated 2D-VMT from natural vermiculite and prepared NiCo2O4 loaded 2D-VMT (NiCo2O4/2D-VMT) catalyst. Levofloxacin (LVX), as a normal antibiotic, was used to evaluate the catalytic capacity of NiCo2O4/2D-VMT in PMS systems. Also, LVX degradation mechanism through NiCo2O4/2D-VMT activated PMS were explored here. XRD, EDS, TEM, and HRTEM analysis all demonstrated NiCo2O4 nanoparticles were successfully anchored on 2D-VMT. NiCo2O4/2D-VMT had a high specific surface area and abundant active sites. The NiCo2O4/2D-VMT/PMS system, with a 15% mass ratio of NiCo2O4 to 2D-VMT (15%-CN/2D-VMT), achieved LVX removal efficiency of 87% and LVX removal rate of 0.034 min−1. 1O2 and SO4·- were the major ROS for LVX degradation. The reversible redox cycle between Co(III)/Co(II) and Ni(III)/Ni(II) played a crucial role in activating PMS to generate ROS for LVX degradation process. Also, based on intermediates identification by LC-MS, possible degradation pathways of LVX were proposed and their ecotoxicological evolution was assessed by using the ECOSAR software. 15%-CN/2D-VMT may be a worth recommended loaded catalyst for antibiotics removal in environmental remediation, owing to its high reusability and excellent renewability.