Remediation of Diesel-Contaminated Soils Using Persulfate Under Alkaline Condition

Abstract

A laboratory study was conducted to assess the feasibility of remediating diesel-contaminated soils using sodium persulfate (SPS) oxidation under an alkaline pH. Lime (CaO) and sodium hydroxide (NaOH) were used as the alkaline sources, and various factors, including temperature, reaction time and concentration level, were investigated. Moreover, the combined usage of hydrogen peroxide (HP) and SPS in the presence or absence of NaOH was also studied. It was found that lime hydration resulted in rapid increases in pH (>12) and temperature (75 °C maximum) at a CaO/H2O mass ratio of 3/20. In the NaOH or CaO/SPS system, the maximum diesel degradation achieved was approximately 30 %. It was observed that using a larger amount of alkaline increased SPS decomposition and had almost no effect on diesel degradation. Limited solubilization of contaminants may have inhibited the effectiveness of alkaline-activated persulfate oxidation during the aqueous phase and hence resulted in incomplete diesel degradation. The highest rate of diesel degradation (i.e., 56 % in 7 days) was achieved using the dual oxidation system, in which a HP/SPS molar ratio of 3.3/0.5 was used. An aggressive oxidation process, coupled with HP, may enhance desorption of diesel from soils and allow oxidation to occur during the aqueous phase.