Resource utilization and recycling of petroleum-contaminated soil by pyrolysis as persulfate activator

Abstract

Oxygen-limited pyrolysis was used to simultaneously remediate and convert petroleum-contaminated soil (PCS) to carbonized soil (CS), which is subsequently reused as a persulfate (PS) activator. The effects of pyrolysis temperature and retention time on the harmlessness of PCS and the PS activation efficiency of CS for aniline (AN) degradation were investigated. When the pyrolysis temperature is 500°C and the retention time is 60 min, the total petroleum hydrocarbon removal rate of PCS and the TOC concentration of CS extracts were 98.96% and 10.2 ppm, respectively. The acute toxicity of CS extracts was classified as non-toxic. The degradation efficiency of AN was up to 96.09% within 6 h. After CS was reused five times, the removal rates of AN and TOC were 53.73% and 51.54%, respectively. The residual organic carbon in CS mainly exists as graphitized carbon, which has good stability and no acute toxicity. The main active species was holes, followed by singlet oxygen. S2O82- is adsorbed on the surface of the positively charged CS and then reduced by electron donor groups to generate holes, which may accelerate electron transfer and facilitate the oxidative degradation of AN. This research provides an innovative alternative disposal strategy for PCS-derivatives treated by pyrolysis, which can simultaneously achieve efficient remediation and high-value reuse of PCS.