# Activation of Persulfate for Groundwater Remediation:
## 4 Factors Affecting the Application of Persulfate in ISCO
### Soil Property  
The capacity to distribute and use oxidants in the subsurface depends heavily on how persulfate interacts with a porous medium. The main factors influencing the effect on the degradation by persulfate are soil texture, minerals, and soil organic matter (SOM) content.  
The soil texture not only affects the transport of persulfate but also can affect the degradation of contaminants. [PERSON] and [PERSON] (2007) conducted alkaline, hydrogen peroxide, and chelated iron activation methods and evaluate the degradation efficiency in a variety of five porous media [125]. They found that the efficiency of persulfate activated by different methods differed in each porous medium, indicating that the characteristics of the porous media affect treatment effectiveness [125]. [PERSON] and [PERSON] (2012) also reported that the PCB can be better degraded in kaolin, while the degradation was insignificantly in glacial till when electro-activated persulfate was applied [106]. The final pH of these two soils was different after remediation. The values of the final pH were around 1 in kaolin but were 7 in glacial till. The low pH also indicated the high consumption of persulfate and better degradation of PCB in kaolin. However, the mechanism of different types of soils impacting the oxidation and the role that soil texture plays in the oxidation process still have not been studied in those studies and need to be further revealed.  
The SOM may have a negative impact on persulfate oxidation for its ability to compete with soil pollutants, resulting in a significant consumption of persulfate [42; 136]. Even more, according to electron paramagnetic resonance (EPR) spectroscopy analysis, [PERSON] (2018) demonstrated that sulfate radicals and hydroxyl radicals can react with SOM and decrease the degradation efficiency [137]. While another study reported that SOM can enhance the degradation of certain pollutants by activating persulfate processes rather than simply exerting a negative effect by consuming persulfate when persulfate was used to remediate benzene in clays, and aquifer solids [74]. Additionally, considerable SOM content has been reported to still be present in the persulfate solution, suggesting that certain organic carbon content may actually be nonreactive with persulfate and its free radical chemistry [138]. Therefore, the effect of SOM on the degradation of persulfate still needs to be further explored, and the types of target pollutants should also be considered in actual remediation applications.  
The mineral phase is a crucial part of the soil because it can interact with organic substances to stabilize organic carbon in soils [139]. Mineral transition metals may react with persulfate to affect contaminant removal efficiency further by either promoting activation or lowering oxidant persistence [85; 86; 140].There are many iron minerals, such as ferrihydrite, ilmenite, hematite, pyrite, goethite, magnetite, and lepidocrocite in the soil, which were observed to have the potential to activate persulfate and make persulfate consumption [85; 86]. For example, the highest consumption of persulfate was observed when pyrite was applied to activate persulfate in a study by [PERSON] et al. (2011). The main reason was that pyrite can be decomposed rapidly in weakly acidic water, providing Fe\({}^{2+}\) to activate persulfate.