Highly efficient removal of trimethoprim based on peroxymonosulfate activation by carbonized resin with Co doping: Performance, mechanism and degradation pathway

We first report the syntheses of carbon-supported Co (CS-Co) composite via a carbonization process from a saturated resin. CS-Co exhibited favorable catalysis activities in activation of peroxymonosulfate (PMS) to generate center dot SO - 4 and center dot OH for trimethoprim (TMP) degradation. The performance of composites were studied with respect to diverse pHs (3.0-9.0), catalyst dosages (0.05-0.5 g/L), PMS dosages (0.05-1.0 mM), TMP concentration (5-20 mg/L) and temperature (15-30 degrees C). Water matrix concerning various levels of humic acid (HA) showed negative effect for TMP removal due to the intrinsic competition between HA. Scavenging test indicated that .SO - 4 and center dot OH were the dominant reactive radicals, and an uncomplicated method to calculate the normalized steady-state concentration of radicals in CS-Co/PMS process was established. The electron transfer concerning PMS, carbon surface and Co2+ was attributed as the main activation mechanism. The main intermediate products of TMP were identified by LC/MS/MS technology with four degradation pathways proposed, including hydroxylation, electron transfer mechanism, demethylation and ring-cleavage.