Application of Ultrasound‐Assisted Supercritical Extraction to Soil Remediation

Abstract

The coupling of ultrasound to supercritical extraction with carbon dioxide has been evaluated as a green remediation technique for soils contaminated with pesticides. The study used samples of soil spiked with atrazine, an organophosphate and contaminant of widespread use. The influence of the operating temperature and pressure on the extraction of atrazine was studied. The extraction of atrazine was enhanced with the use of ultrasound relative to the results obtained from conventional supercritical extraction. This study, operated in semi-continuous mode, demonstrates the possibility of increasing the yield of supercritical extraction by coupling with ultrasound instead of adding co-solvents, which is a greener alternative for removing contaminants such as pesticides from soil matrices.

Ultrasonics and sonochemistry: Editors’ perspective

“…US is usually combined with other treatments in soil environmental remediation as it does not deliver the desired pollutant degradation as a standalone method [87] . These complementary methods may include traditional physicochemical processes, such as soil washing [87] , persulfate [88] , or more advanced methods, such as advanced oxidation processes (ozone, [86] ) and supercritical extraction [89] . Song et al [87] remediated a model of polluted soil containing phenanthrene concentrations from 0.0125 to 0.05 wt%, using a combination of soil water washing and US at 20 kHz (power unspecified).…”

“…Castelo-Grande et al [89] used pre-treated soil samples contaminated with 150–210 ppm of atrazine as a feedstock. 32–35 g of sample were contacted with CO 2 at 100–245 bar (70 and 80 mL min −1 ) and 30–60 °C (supercritical CO 2 ).…”