Abstract
Remediation of hydrocarbon contaminated soils can be performed both in situ and ex situ using chemical oxidants such as sodium persulfate. Standard methods for quantifying persulfate require either centrifugation or prolonged settling times. An optimized soil extraction procedure was developed for persulfate involving simple water extraction using a modified disposable syringe. This allows considerable saving of time and removes the need for centrifugation. The extraction time was reduced to only 5 min compared to 15 min for the standard approach. A comparison of the two approaches demonstrated that each provides comparable results. Comparisons were made using high (93 g kg−1 soil) and low (9.3 g kg−1 soil) additions of sodium persulfate to a petroleum hydrocarbon-contaminated soil, as well as sand spiked with diesel. Recoveries of 95±1% and 96±10% were observed with the higher application rate in the contaminated soil and spiked sand, respectively. Corresponding recoveries of 86±5% and 117±19% were measured for the lower application rate. Results were obtained in only 25 min and the method is well suited to batch analyses. In addition, it is suitable for application in a small field laboratory or even a mobile, vehicle-based system, as it requires minimal equipment and reagents.
Highlights
Chemical oxidation is most commonly applied as an in situ remediation technology but may be applied ex situ to contaminated soils [1,2,3]
Persulfate salts such as sodium persulfate (Na2S2O8) dissociate to the persulfate anion S2O822, which has a standard oxidation potential (Eu) of 2.01 V
The manufacturers highlight the possibility of interferences from hydrogen peroxide or ferrous ions, which are commonly used as activators of persulfate, as well as from cupric ions
Summary
Chemical oxidation is most commonly applied as an in situ remediation technology but may be applied ex situ to contaminated soils [1,2,3]. Permanganates and peroxides [1]. Persulfate salts such as sodium persulfate (Na2S2O8) dissociate to the persulfate anion S2O822, which has a standard oxidation potential (Eu) of 2.01 V. Liang et al [4] reviewed available methods for determination of persulfate in aqueous samples and presented a rapid spectrophotometric method that produced results after approximately 20 min. This represented a considerable time saving over previous techniques described by Shuiundu et al [5] and Huang et al [6]. The addition of an efficient extraction step to the rapid spectrophotometric method of Liang et al [4] would provide a valuable tool for assessing persulfate concentrations in soils
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