The question of whether Fe(IV) or SO₄^•– is the dominant intermediate in the Fe(II)-activated peroxydisulfate process [Fe(II)/PDS process] remains unanswered. In this study, besides Fe(IV), SO₄^•– and HO^• were shown to be produced in the Fe(II)/PDS process by using multiple probes [dimethyl sulfoxide, methyl phenyl sulfoxide, p-nitrobenzoic acid (p-NBA), and benzoic acid (BA)]. The removal of p-NBA and BA and the influence of BA on the yield of methyl phenyl sulfone (PMSO₂) indicated that the major oxidizing intermediate changed from Fe(IV) to SO₄^•–/HO^• with an increase in the PDS/Fe(II) molar ratio at pH 3.0. Fe(IV), SO₄^•–, and HO^• were all involved in this process at pH 3.0–6.5, but their available amounts that contributed to abating organic contaminants decreased with an increase in pH considering the influence of pH on the generation of PMSO₂ and p-hydroxybenzoic acid. Furthermore, Fe(IV), SO₄^•–, and HO^• contributed differently to abating different organic contaminants because of the different reactivities of these oxidizing oxidants toward different organic contaminants. Overall, this study demonstrates that multiple oxidizing species [Fe(IV), SO₄^•–, and HO^•] are generated in the Fe(II)/PDS process, which was significant for the application of this process and understanding the mechanisms of Fe(II)-activated peroxide processes.

中文翻译：

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Fe（IV）和自由基都是Fe（II）/过氧二硫酸盐工艺中的活性氧化剂

Fe（IV）或SO ₄ ^•–是Fe（II）活化的过氧二硫酸盐工艺[Fe（II）/ PDS工艺]中的主要中间体的问题仍未得到解答。在这项研究中，除了铁（IV），SO ₄ ^{• -}和HO ^•示于铁（II）/ PDS处理要生产通过使用多个探针[二甲亚砜，甲基苯基亚砜，p -硝基苯甲酸（p - NBA）和苯甲酸（BA）]。p -NBA和BA的去除以及BA对甲基苯基砜（PMSO ₂）产量的影响表明，主要的氧化中间体从Fe（IV）变为SO ₄ ^•- / HO ^•在pH 3.0时PDS / Fe（II）摩尔比增加。Fe（IV），SO ₄ ^•和HO ^•都在pH 3.0-6.5时参与了该过程，但是考虑到pH对pH生成的影响，其有助于减少有机污染物的可用量随pH的增加而降低。 PMSO ₂和对羟基苯甲酸。此外，由于这些氧化剂对不同有机污染物的反应性不同，因此Fe（IV），SO ₄ ^•和HO ^•对减少不同有机污染物的贡献也不同。总的来说，这项研究表明多种氧化性物质[Fe（IV），SO ₄ ^•–和HO^•是在Fe（II）/ PDS工艺中生成的，对于该工艺的应用和理解Fe（II）活化的过氧化物工艺的机理非常重要。