Efficient oxidation of high levels of soil-sorbed phenanthrene by microwave-activated persulfate: implication for in situ subsurface remediation engineering

Abstract

Purpose In situ chemical oxidation using activated persulfate is increasingly applied for source destruction of hydrophobic organic contaminants (HOCs), e.g., PAHs, the target group contaminants of this study. However, the low aqueous solubility and strong sequestration of HOCs by soil aggregates are major hurdles for the oxidation of HOCs in the subsurface. This study aimed to investigate the potential of using microwave-activated persulfate to tackle the above issues and accelerate the remediation of HOC-contaminated sites. Materials and methods Soil sorbed with high levels of phenanthrene, a model compound for PAHs, was used in the study. The effects of microwave, reaction temperature, reaction time, oxidant dosage, and soil to water ratio on the destruction of phenanthrene, persulfate consumption, and slurry pH were studied. Furthermore, the mechanisms of the microwaveactivated process were discussed by comparing the degradation results using microwave-activated persulfate with those using conventional heat-activated persulfate, and potential microwave-specific effects were explored.Results and discussion This study shows that microwaveactivated persulfate is highly effective toward the destruction of high levels of soil-sorbed phenanthrene. The results indicate that higher slurry temperature is critical to initiate a positive feedback loop that induces rapid and efficient destruction of phenanthrene. Furthermore, potential mechanisms of the positive feedback loop were discussed. Though persulfate is mainly activated by the thermal effect of microwave, nonthermal microwave-specific effects were preliminary observed, which induce additional activation of persulfate and further enhance the destruction efficiency of phenanthrene. In addition, how to integrate an in situ microwave soil heating system with the traditional persulfate remediation process for subsurface engineering was discussed to provide guidance for potential applications in field scales. Conclusions Overall, the feasibility of using microwave heating to accelerate persulfate remediation of subsurface organic contaminations was established.

Efficient degradation of Acid Orange 7 by persulfate activated with a novel developed carbon‐based MnFe2O4 composite catalyst

“…[8][9][10] Thus it was significant to explore the generation of SO 4 −• for its wide application. SO 4 −• was normally produced by the activation of peroxymonosulfate (PMS) or persulfate (PS) 11 via a variety of methods such as heat, 12 ultrasound, 13 ultraviolet irradiation, 14 microwave, 15 alkali 16 and transition metal catalysis. 17,18 Among various activation technologies, different transition metals were extensively studied for their excellent performance.…”

Geoenvironmental characteristics of bisphenol A contaminated soil after persulfate treatment with different activation/enhancement methods

“…Sulfate radical (SO 4 − ·) is a strong one-electron oxidant with a high redox potential of 2.5–3.1 V and is nonselective for mineralization of a range of organic compounds [4]. The stimulation, also called activator, has been investigated in aspect of UV [5], heat [6], base [7], transition metals [8], minerals [9], sonochemistry [10], citric acid [11], electrochemical [12], nanocarbons [13], and quinones [14]. The generated sulfate radical can spontaneously and rapidly oxidize organics and ultimately transform to sulphate ion as the by-products [15]: …”

Formation of Developmentally Toxic Phenanthrene Metabolite Mixtures by Mycobacterium sp. ELW1

“…39–43 In addition, PHE is commonly described as a prototype PAH due to the replication of its 3-ring structure throughout higher-ringed, more carcinogenic PAHs, such as benzo[a]pyrene. 40–42 PHE has also been used as a model PAH for human metabolism studies because its bay-region and K-region lead to the possible formation of more carcinogenic PAHs.…”

“…40–42 PHE has also been used as a model PAH for human metabolism studies because its bay-region and K-region lead to the possible formation of more carcinogenic PAHs. 39,43 PHE also has a moderate aqueous solubility of 6.73 µmol L −1 , compared to the range of aqueous solubilities for other parent PAHs (0.003 to 234 µmol L −1 ), and this is important for bioremediation studies in aqueous systems. 16,17 …”