Department of Civil and Environmental Engineering and §Department of Material Science and Engineering, University of California at Berkeley , Berkeley, California 94720, United States.
Environ Sci Technol. 2014 Sep 2;48(17):10330-6. doi: 10.1021/es502056d. Epub 2014 Aug 18.
Persulfate (S2O8(2-)) is being used increasingly for in situ chemical oxidation (ISCO) of organic contaminants in groundwater, despite an incomplete understanding of the mechanism through which it is converted into reactive species. In particular, the decomposition of persulfate by naturally occurring mineral surfaces has not been studied in detail. To gain insight into the reaction rates and mechanism of persulfate decomposition in the subsurface, and to identify possible approaches for improving its efficacy, the decomposition of persulfate was investigated in the presence of pure metal oxides, clays, and representative aquifer solids collected from field sites in the presence and absence of benzene. Under conditions typical of groundwater, Fe(III)- and Mn(IV)-oxides catalytically converted persulfate into sulfate radical (SO4(•-)) and hydroxyl radical (HO(•)) over time scales of several weeks at rates that were 2-20 times faster than those observed in metal-free systems. Amorphous ferrihydrite was the most reactive iron mineral with respect to persulfate decomposition, with reaction rates proportional to solid mass and surface area. As a result of radical chain reactions, the rate of persulfate decomposition increased by as much as 100 times when benzene concentrations exceeded 0.1 mM. Due to its relatively slow rate of decomposition in the subsurface, it can be advantageous to inject persulfate into groundwater, allowing it to migrate to zones of low hydraulic conductivity where clays, metal oxides, and contaminants will accelerate its conversion into reactive oxidants.
过硫酸盐（S2O8(2-)) 越来越多地被用于地下水的原位化学氧化（ISCO），以处理有机污染物，尽管其转化为反应性物质的机制尚未完全了解。特别是，过硫酸盐在天然存在的矿物表面的分解尚未得到详细研究。为了深入了解地下水中过硫酸盐分解的反应速率和机制，并确定提高其效率的可能方法，在有苯和无苯存在的情况下，研究了纯金属氧化物、粘土和从现场采集的代表性含水层固体存在时过硫酸盐的分解情况。在地下水条件下，Fe(III) 和 Mn(IV) 氧化物在数周的时间内催化将过硫酸盐转化为硫酸根自由基（SO4(•-)) 和羟基自由基（HO(•))，反应速率比无金属体系中的反应速率快 2-20 倍。非晶态水铁矿是最具反应活性的铁矿物，其过硫酸盐分解速率与固体质量和表面积成正比。由于自由基链式反应，当苯浓度超过 0.1mM 时，过硫酸盐的分解速率最高可增加 100 倍。由于过硫酸盐在地下水中的分解速度相对较慢，因此将过硫酸盐注入地下水并使其迁移到低水力传导率的区域是有利的，在这些区域中，粘土、金属氧化物和污染物将加速过硫酸盐转化为反应性氧化剂。
