Enhanced degradation of total petroleum hydrocarbons in real soil by dual-frequency ultrasound-activated persulfate

Ultrasound (US) can be employed to activate persulfate (PS) for degrading total petroleum hydrocarbons (TPH). In this study, to improve the degradation efficiency, PS is combined with dual-frequency US (DFUS) towards synergistic degradation of TPH in real soil. After 180 min, the degradation percent...

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Bibliographic Details
Published in:The Science of the total environment 2020-12, Vol.748, p.141414-141414, Article 141414
Main Authors: Lei, Yong-Jia, Zhang, Jun, Tian, Yu, Yao, Jing, Duan, Qiu-Shi, Zuo, Wei
Format: Article
Language:English
Subjects:
Dual-frequency ultrasound
Persulfate
Petroleum
Radicals
Soil
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Summary:Ultrasound (US) can be employed to activate persulfate (PS) for degrading total petroleum hydrocarbons (TPH). In this study, to improve the degradation efficiency, PS is combined with dual-frequency US (DFUS) towards synergistic degradation of TPH in real soil. After 180 min, the degradation percentages for DFUS/PS, DFUS, high-frequency US and high-frequency US/PS are around 88.9%, 38.7%, 7.3% and 54.2%, respectively. Additionally, the influence of US power, PS content, slurry pH and temperature, and TPH components on the degradation percentage in the DFUS/PS process are explored. Scanning electron microscopy (SEM) images and the results of specific surface area verify that the DFUS can break the soil aggregates more effectively than the single-frequency US, and thus enhance the TPH desorption and accelerate the oxidant diffusion. Moreover, the investigation of the mechanism is further evaluated through quenching and electron spinning resonance spectrum (ESR) tests. The results indicate that the generation of SO4− and OH in DFUS/PS is ~1.6 times and ~2.5 times as much, respectively, as in high frequency US/PS. The relative contributions to the synergistic TPH degradation in the DFUS/PS system are: SO4− (PS activation via the heat induced by US) > pyrolysis inside the bubbles (hydrophobicity of TPH) > SO4− (PS activation via US cavitation) >OH. Finally, the hypothesis is confirmed via the evaluation of the degradation kinetics, which shows that the combined process of DFUS/PS is not a simple addition of the US and PS, but provides a highly effective process of synergistic degradation. [Display omitted] •DFUS/PS is efficient for high-lever TPH degradation in real soil (~88.9%).•DFUS smashes the soil aggregates more effectively than single-frequency US.•DFUS/PS generates more radicals (SO4− and OH) than single-frequency US/PS.•SO4− (PS thermal activation from US) is mainly responsible for TPH degradation.
ISSN:0048-9697
1879-1026
DOI:10.1016/j.scitotenv.2020.141414