title: Kinetic and mechanistic investigations of the degradation of sulfamethazine in heat-activated persulfate oxidation process.
abstract: Sulfamethazine (SMZ) is widely used in livestock feeding and aquaculture as an antibiotic agent and growth promoter. Widespread occurrence of SMZ in surface water, groundwater, soil and sediment has been reported. In this study, degradation of SMZ by heat-activated persulfate (PS) oxidation was investigated in aqueous solution. Experimental results demonstrated that SMZ degradation followed pseudo-first-order reaction kinetics. The pseudo-first-order rate constant (kobs) was increased markedly with increasing concentration of PS and temperature. Radical scavenging tests revealed that the predominant oxidizing species was SO4·(-) with HO playing a less important role. Aniline moiety in SMZ molecule was confirmed to be the reactive site for SO4·(-) attack by comparison with substructural analogs. Nontarget natural water constituents affected SMZ removal significantly, e.g., Cl(-) and HCO3(-) improved the degradation while fulvic acid reduced it. Reaction products were enriched by solid phase extraction (SPE) and analyzed by liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (LC-ESI-MS/MS). 6 products derived from sulfonamide S--N bond cleavage, aniline moiety oxidation and Smiles-type rearrangement were identified, and transformation pathways of SMZ oxidation were proposed. Results reveal that heat-activated PS oxidation could be an efficient approach for remediation of water contaminated by SMZ and related sulfonamides.
authors.affiliation: College of Resources and Environmental Science, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Fan
authors.affiliation: College of Resources and Environmental Science, Nanjing Agricultural University, Nanjing 210095, China. Electronic address: yuefeiji@njau.edu.cn.
authors.forename: Yuefei
authors.initials: Y
authors.lastname: Ji
authors.affiliation: Nanjing Institute of Environmental Science, Ministry of Environmental Protection of PRC, Nanjing 210042, China.
authors.forename: Deyang
authors.initials: D
authors.lastname: Kong
authors.affiliation: College of Resources and Environmental Science, Nanjing Agricultural University, Nanjing 210095, China. Electronic address: jhlu@njau.edu.cn.
authors.forename: Junhe
authors.initials: J
authors.lastname: Lu
authors.affiliation: College of Resources and Environmental Science, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Quansuo
authors.initials: Q
authors.lastname: Zhou
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry*; D002853:Chromatography, Liquid; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010084:Oxidation-Reduction; D017680:Potassium Compounds / Q000737:chemistry*; D052616:Solid Phase Extraction; D021241:Spectrometry, Mass, Electrospray Ionization; D013418:Sulfamethazine / Q000737:chemistry*; D013431:Sulfates / Q000737:chemistry*; D053719:Tandem Mass Spectrometry; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods
chemical_list: D000890:Anti-Infective Agents; D017680:Potassium Compounds; D013431:Sulfates; D014874:Water Pollutants, Chemical; D013418:Sulfamethazine; C009007:potassium persulfate
keywords: Heat-activated persulfate oxidation; Reaction products; Sulfamethazine; Sulfate radical; Transformation mechanisms