Persulfate (peroxydisulfate, S₂O₈²⁻) is the newest oxidant used for the in situ chemical oxidation (ISCO) remediation of soil and groundwater. The present study investigated impacts of solution pH, temperature, and persulfate concentration on the reaction rate constant (k₁), activation energy (E_a), and reaction order of the heat-activated persulfate process. Phenol was chosen as the model organic contaminant. As temperature increased from 30 °C to 70 °C, k₁ exhibited a significant increase from 0.003 h⁻¹∼0.962 h⁻¹ (pH 1.3–13.9) to 1.184 h⁻¹∼9.91 h⁻¹ (pH 1.3–13.9), which corroborated with the activation of persulfate using heat. As pH increased from 1.3 to 13.9, k₁ exhibited a 4.3-fold increase at 70 °C and a 320-fold increase at 30 °C, thereby suggesting that: 1) the phenol oxidation rate increased under alkaline conditions, and 2) the enhancement of reaction rate due to alkaline activation was more pronounced at a lower temperature. Increasing pH significantly reduced E_a from 139.7 ± 1.3 kJ/mol at pH 1.3 to 52.0 ± 3.3 kJ/mol at pH 13.9. In contrast to changing pH, increasing persulfate concentration from 20 to 320 mM significantly increased k₁ but did not affect E_a. Changes in E_a suggest that persulfate oxidation of phenol experienced different reaction pathways or elementary reaction sequences as the pH changed from 1.3 to 13.9. In addition, the k₁ and E_a data also suggest that a minimal pH threshold of ∼11 was required for the effective alkaline activation of persulfate.

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pH和温度变化对苯酚的热活化过硫酸盐氧化的活化能和动力学的影响

过硫酸盐（过氧二硫酸盐，S ₂ O ₈ ^2-）是用于土壤和地下水原位化学氧化（ISCO）修复的最新氧化剂。本研究研究了溶液pH，温度和过硫酸盐浓度对热活化过硫酸盐过程的反应速率常数（k ₁），活化能（E _a）和反应顺序的影响。选择苯酚作为模型有机污染物。随着温度从30℃升高至70℃，ķ ₁显示出从0.003 h的显著增加^-1 ~0.962ħ ^-1（pH值1.3-13.9），以1.184ħ ^-1 ~9.91ħ ^-1（pH 1.3–13.9），这与加热过硫酸盐的活化有关。随着pH从1.3增加到13.9，k ₁在70°C时显示4.3倍的增加，在30°C时显示320倍的增加，从而表明：1）碱性条件下苯酚的氧化速率增加，2）在较低的温度下，由于碱活化而引起的反应速率的增强更为显着。增加pH值会使E _a从pH 1.3的139.7±1.3 kJ / mol降低到pH 13.9的52.0±3.3 kJ / mol。与改变pH值相反，将过硫酸盐浓度从20 mM增加到320 mM可以显着增加k _1，但不会影响E _a。E _a的变化这表明，随着pH从1.3变为13.9，苯酚的过硫酸盐氧化经历了不同的反应途径或基本反应顺序。此外，k ₁和E _a数据还表明过硫酸盐的有效碱活化需要最低pH阈值为〜11。