甲氧苄啶在有机酸络合Fe2+活化过硫酸钠体系中的降解机制
Degradation mechanism of trimethoprim by organic acid chelating Fe2+-activated sodium peroxydisulfate
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摘要: 在有机酸(OAS)/Fe2+/过硫酸钠(PDS)体系中生成的具有强氧化能力的硫酸根自由基(SO4·-),可以降解水中难降解污染物甲氧苄啶(TMP).分别探讨了柠檬酸(CA)浓度、Fe2+浓度、PDS浓度、pH值对甲氧苄啶降解的影响,以及不同浓度的4种有机酸在不同pH值下对TMP降解的影响.结果表明,当TMP浓度20 μmol·L-1,pH=7,温度25℃,反应时间30 min,摩尔比CA:Fe2+:PDS:TMP=5:15:40:1时,TMP的降解率高达82.55%;柠檬酸和EDTA有促进TMP降解作用,焦磷酸钠和草酸起抑制TMP降解作用.猝灭实验证实了TMP的降解是SO4·-和·OH共同作用的结果,SO4-·起主导作用;液相色谱质谱检出5种中间产物,推测TMP的降解路径涉及羟基化反应、脱甲氧基化反应和裂解反应.Abstract: The organic acid/Fe2+/sodium peroxydisulfate (PDS) system for the degradation of trimethoprim (TMP) was investigated. The degradation is based on the generation of sulfate radicals anion (SO4·-), which have strong oxidation capability. The effect of initial concentrations of CA, Fe2+, PDS, pH, and concentration of organic acids under different pH on the removal of TMP were investigated. The results showed that the maximum degradation efficiency of TMP reached 82.55% at the molar radio of CA:Fe2+:PDS:TMP=5:15:40:1 within 30 min under the experimental initial condition of TMP=20 μmol·L-1, pH=7 and 25℃. Citric acid and EDTA had positive effects on the degradation of TMP, but sodium pyrophosphate and oxalic acid had negative effects on the degradation of TMP. The results of quenching experiments confirmed that the oxidizing species for TMP degradation were attributed to SO4·- and ·OH, in which SO4·- played a leading role. Five intermediates were identified by employing liquid chromatography-mass spectrometry (LC/MS) techniques, and it was speculated that the degradation pathway of TMP involved hydroxylation, demethylation and cleavage.
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Key words:
- organic acid /
- ferrous ions /
- sulfate radical anion /
- sodium persulfate /
- trimethoprim
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