title: Degradation of toluene-2,4-diamine by persulphate: kinetics, intermediates and degradation pathway.
abstract: In this study, the degradation of toluene-2,4-diamine (TDA) by persulphate (PS) in an aqueous solution at near-neutral pH was examined. The result showed that the degradation rate of TDA increased with increasing PS concentrations. The optimal dosage of PS in the reaction system was determined by efficiency indicator (I) coupling in the consumption of PS and decay half-life of TDA. Calculation showed that 0.74 mM of PS was the most effective dosage for TDA degradation, at that level the maximum I of 24.51 was obtained. PS can oxidize TDA for an extended reaction time period. Under neutral condition without activation, four degradation intermediates, 2,4-diamino-3-hydroxy-5-sulfonicacidtoluene, 2,4-diaminobenzaldehyde, 2,4-bis(vinylamino)benzaldehyde and 3,5-diamino-4-hydroxy-2-pentene, were identified by high-performance liquid chromatography-mass spectrometry. The tentative degradation pathway of TDA was proposed as well. It was found that hydroxyl radical played an important role in degradation of TDA with the activation of Fe2+, whereas PS anion and sulphate radicals were responsible for the degradation without activation of Fe2+.
authors.affiliation: a State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences , Beijing 100012 , People's Republic of China.
authors.forename: Yong-hai
authors.initials: YH
authors.lastname: Jiang
authors.forename: Jin-bao
authors.initials: JB
authors.lastname: Zhang
authors.forename: Bei-dou
authors.initials: BD
authors.lastname: Xi
authors.forename: Da
authors.initials: D
authors.lastname: An
authors.forename: Yu
authors.initials: Y
authors.lastname: Yang
authors.forename: Ming-xiao
authors.initials: MX
authors.lastname: Li
mesh_terms: D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D007700:Kinetics; D010655:Phenylenediamines / Q000737:chemistry*; D013431:Sulfates / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D010655:Phenylenediamines; D013431:Sulfates; D014874:Water Pollutants, Chemical; C007303:2,5-diaminotoluene; D007501:Iron
keywords: 4-diamine; degradation intermediates; hydroxyl radical; persulphate oxidation; sulphate radical; toluene-2