Utility and mechanism of magnetic nano-MnFe2O4/MWNT activation for oxidative degradation of tetracycline by persulfate.

Abstract

A magnetic MnFe2O4/MWNT nanocomposite activated with sodium persulfate (PDS) was investigated for the removal of the widely used antibiotic tetracycline (TC). The best-performing 80 wt.% MnFe2O4/MWNT nanocomposite was screened for catalytic degradation of TC by comparing the catalytic and adsorption processes. The nanocomposite was evaluated using a series of physical characterizations. The effects of catalyst dosage, PDS dosage, temperature, initial pH, and initial concentration of TC on TC removal were investigated. After the reaction for 90min, the addition of 4mM PDS to the 80 wt.% MnFe2O4/CNT catalyst at 0.5g/L degraded 78.85% of TC and 51.97% of TOC at an initial TC concentration of 40mg/L. The reusability of MnFe2O4/MWNT nanocomposite was evaluated and the structural stability of the material was verified. It was demonstrated that multiple active species (SO4-, ·OH, ·O2-, 1O2) were produced in the MnFe2O4/MWNT/PDS system. The catalytic mechanism was analyzed based on the XPS results. Total organic carbon (TOC) measurement indicated partial TC had completely mineralized. The presumable degradation pathway of TC was proposed according to intermediate products by the LC-MS method.