Enhanced transition metal oxide based peroxymonosulfate activation by hydroxylamine for the degradation of sulfamethoxazole

The enhanced peroxomonosulfate (PMS) activation and sulfamethoxazole (SMZ) degradation performances and mechanisms by hydroxylamine (HA) in the presence of three transition metal oxides (M x O y ), hematite (α-Fe 2 O 3 ), cobalt oxide (Co 2 O 3 ) and copper oxide (CuO) were comprehensive investigated. The results showed that proper addition of hydroxylamine (HA) can greatly promote the degradation of SMZ in the three M x O y /PMS systems. The results of electron paramagnetic resonance (EPR) study and quenching experiment suggested that OH was the dominating reactive oxygen species (ROS) in the α-Fe 2 O 3 /HA/PMS and Co 2 O 3 /HA/PMS systems, while in CuO/HA/PMS system, the activated-PMS on the surface of CuO was concluded to be responsible for SMZ degradation instead of free radicals. Furthermore, the intermediates of SMZ in the systems were detected by a high performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) and the degradation pathways of SMZ system were inferred, the results indicated that due to the difference of the dominating ROS and the attack order against oxidation sites, SMZ was degraded in different pathways in α-Fe 2 O 3 /HA/PMS, Co 2 O 3 /HA/PMS and CuO/HA/PMS system. α-Fe 2 O 3 , CuO and Co 2 O 3 , could maintain stable catalytic activity in the respective reaction systems and could be efficiently recycled.