无机阴离子对类-Fenton反应的影响

The effects of inorganic anions on Fenton-like reactions of atrazine and phenol

对比研究了4种常见无机阴离子(ClO4-、NO3-、Cl-和SO24-)对类-Fenton反应中H2O2分解和有机物(莠去津=2.1μmol.L-1和苯酚=50μmol.L-1)降解的影响.实验在pH=3.00±0.05(25℃)条件下完全混合反应器中进行.结果表明,在类-Fenton反应过程中,ClO4-和NO3-的存在对H2O2分解和有机物降解几乎没有影响;在不存在有机物条件下,Cl-和SO42-的加入使得H2O2分解速率显著降低,ClO4-≈NO3->Cl->SO24-;莠去津存在条件下,莠去津降解速率为ClO4-≈NO3->Cl->SO24-,而H2O2分解速率为ClO4-≈NO3-≈Cl->SO24-;苯酚存在条件下,苯酚和H2O2的降解速率为ClO4-≈NO3-≈SO42->Cl-.无机阴离子对类-Fenton反应的影响一方面是由于Cl-和SO42-与Fe3+发生络合反应,阻碍了Fe3+与H2O2络合物的形成,减少了.OH的产生;另一方面Cl-和SO42-消耗.OH,形成较低氧化活性的无机自由基(SO4.-和Cl2.-);同时,根据类-Fenton反应降解有机物的不同,无机阴离子对类-Fenton反应的影响也有所不同.

The effects of perchlorate, nitrate, chloride and sulfate ions on the rates of the decomposition of H2 02 and the oxidation of organic compounds （ [ atrazine] 0 = 2.1 μmol·L^ -1, [ phenol] 0 = 50 μmol· L^ -1 ） by Fenton-like processes were investigated. Experiments were conducted in a completely mixed reactor at pH = 3.00 - 0.05 （25 ℃ ）. Data obtained from the Fenton-like experiments showed that the degradation rate of organics and H2O2 were not affected significantly in the presence of perchlorate and nitrate ions; whereas the presence of sulfate or chloride markedly decreased the rates of decomposition of H2O2 in the absence of organic solutes. The rates of reaction between Fe^3 ＋ and H2O2 followed the order ClO4-≈NO3-≈Cl-〉SO4^2-. The rates of depletion of atrazine followed the order ClO4-≈NO3-≈Cl-〉SO4^2- and the rates of decomposition of H2O2 in the presence of atrazine in aqueous solution were ClO4-≈NO3-≈Cl-〉SO4^2-. In the phenol system, the rates of degradation of phenol and H2O2 followed the order ClO4-≈NO3-≈SO4^2-〉Cl^-. These inhibitory effects by inorganic anions are attributed to （i） the decrease of the rate of generation of hydroxyl radicals resulting from formation of complexes between Fe^3 ＋ and sulfate or chloride ions; （ii） formation of less reactive inorganic radicals （SO4^- - and Cl2^- ） resulting from competitive reactions between the hydroxyl radicals and sulfate or chloride ions. The impact of inorganic anions on Fenton-like reaction was also dependent on the characteristics of the model organic compounds in the system.