Natural Persulfate Activation for Anthracene Remediation in Tropical Environments

Ferreira, IedaD.; Prieto, Tatiana; Freitas, JulianaG.; Thomson, NeilR.; Nantes, IseliL.; Bechara, EtelvinoJ. H.

Natural Persulfate Activation for Anthracene Remediation in Tropical Environments

2017

In situ chemical oxidation using persulfate is one alternative to remediate polycyclic aromatic hydrocarbon-contaminated soil; however, oxidation can lead to the formation of toxic and persistent by-products, and treatment efficiency can be dependent on environmental conditions. Temperature and soil matrix properties can dictate reaction rates and pathways, promoting oxidant activation or scavenging the free radicals generated. This research investigated the ability of persulfate to degrade anthracene in tropical environmental conditions. Batch tests were conducted for various persulfate systems (naturally and chelated-iron-activated), with an Oxisol contaminated with anthracene. Electron paramagnetic resonance (EPR) was used to identify free radicals formed. Naturally activated persulfate degraded more than 96% of the anthracene and its by-product anthraquinone after 90 days, considered more toxic and persistent, while the chelated-iron-activated persulfate system used was able to remove 70% of the anthracene. EPR measurements showed the coexistence of SO₄·⁻ and ·OH radicals. Sulfate radicals were formed by thermal activation at ambient temperatures (mean of 23.7 °C), and ·OH was formed by propagation reactions and hydrolysis in acidic conditions that lead to peroxide formation. In the naturally activated system, anthracene degradation was observed and SO₄·⁻ radicals were abundant, indicating that this treatment system can be effective in a typical tropical soil environment.

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