Insights into the oxidation kinetics and mechanism of diesel hydrocarbons by ultrasound activated persulfate in a soil system

Diesel hydrocarbons (DHC) can be oxidised by persulfate (PS) once activated. Ultrasonic (US) can also oxidise DHC in a water system by generating ·OH due to hydrolysis at micro cavitation. In this study, US was combined with PS towards synergic oxidation of DHC in a soil system. Various factors which would affect the oxidation of DHC have been evaluated, including DHC and PS concentration, US power intensity, operating temperature and pH, as well as inorganic anions and humic acid (HA). The kinetic parameters were investigated using a demisemi-lives method, and the results indicated that the DHC degradation rate could be expressed as r=1.4Lg^-1min^-1[DHC]⁰[PS]. The results also revealed that increasing the content of DHC, Cl^-, HCO₃̅ and HA would inhibit the removal of DHC. An acidic condition and high US power were shown to facilitate the DHC degradation. Finally, the DHC degradation mechanism was examined using radical quenching and ESR (electron spinning resonance spectrum) experiments, which showed that the SO·₄̅ generated through the heat induced by US was the predominant oxidising species and main contributor to the synergic oxidation.