Mechanism study of nitrilotriacetic acid-modified premagnetized Fe0/H2O2 for removing sulfamethazine

Abstract

Sulfamethazine (SMT) is extensively used as growth promoters and antibacterial drugs. In this study, premagnetized Fe0 was used to catalyze H2O2 decomposition (pre-Fe0/H2O2) in the presence of nitrilotriacetic acid (NTA) to remove SMT at neutral pH conditions. In all, 30.3% and 99.8% of SMT were removed by the pre-Fe0/H2O2 process (60 min) and the pre-Fe0-NTA/H2O2 process (30 min), respectively. The removal rate of SMT in the pre-Fe0-NTA/H2O2 process was 2.5 times larger than that in the Fe0-NTA/H2O2 process. Electron paramagnetic resonance signals indicated that more radicals were generated in the pre-Fe0-NTA/H2O2 system. SMT and NTA and their degradation by-products adsorbed on pre-Fe0 reduced the contact angle of the particle and prevented the formation of Fe3O4 on the particle surface, thus accelerating Fe0 corrosion. Tafel scan images confirmed the enhancement of Fe0 corrosion in the presence of NTA and magnetic field. The Fe0 corrosion rate (109) after 20 min of reaction was 6.61 cm/s in pre-Fe0-NTA/H2O2, much higher than that in Fe0/H2O2 (0.73 cm/s), pre-Fe0/H2O2 (1.47 cm/s) and Fe0-NTA/H2O2 (2.94 cm/s). Pre-Fe0-NTA/H2O2 could also keep the fast SMT removal with eight consecutive runs without the addition of pre-Fe0 and NTA and presented high efficiency for SMT removal in real municipal wastewater.