Fe-Activated Peroxymonosulfate Enhances the Degradation of Dibutyl Phthalate on Ground Quartz Sand

Soil contamination by organic compounds has received worldwide concern for decades. Here, we found that dibutyl phthalate (DBP) could be degraded on moist quartz sand (QS, crystal, a typical soil constituent) during stirring, and the removal rate reached 57.2 ± 3.1% after 8 h of reaction. The introduction of peroxymonosulfate (PMS) and zerovalent iron (Fe⁰) substantially improved the decomposition of DBP to 94.2 ± 1.6% in 8 h, suggesting they have great contributions. DBP decomposition was caused by multiple reactive species, such as surface silicon-based radicals (like ≡SiO^•) and other reactive species like superoxide radical (O₂^•-), hydroxyl radical (^•OH), and sulfate radical (SO₄^•-). In the QS/ultrapure water system, DBP was mainly attacked by O₂^•- or ≡SiO^•, with the formation of hydrolysis products. In the iron@QS/PMS system, due to the activation of PMS by Fe⁰, SO₄^•- and ^•OH were produced while the latter led to DBP degradation, and thus hydroxyl substitution products of DBP were ubiquitous. DBP was hardly removed on amorphous supporters like silica gel, alumina, and red soil even with the presence of PMS and Fe⁰, indicating the indispensable role of surface radicals on crystals like QS. This work presents a new remediation technology for polluted soil, especially aquifer.