Ultrasonic Enhanced Desorption of DDT from Contaminated Soils
2011
Thangavadivel, Kandasamy | Megharaj, Mallavarapu | Smart, Roger St. C. | Lesniewski, Peter J. | Bates, Darren | Naidu, R.
In this study, using high-power low-frequency ultrasound, heated slurries with anionic surfactant sodium dodecyl sulfate (SDS) were treated to enhance desorption of DDT from soils with high clay, silt, and organic matter content and different pH (5.6–8.4). The results were compared with DDT extracted using a strong solvent combination as reference. Slurry ranges from 5 to 20Â wt.% were studied. For a soil slurry (10Â wt.%) at pHÂ 6.9 with 0.1% v/v SDS surfactant heated to 40°C for 30Â min, desorption was above 80% in 30Â s using 20Â kHz, 932 W/L ultrasonic intensity without solvent extraction. Other soils gave lower desorption efficiency in the range 40–60% after 30Â s ultrasonic treatment. The percentage of organic matter, dissolved organic carbon, soil surface area, clay and silt percentage, and soil pH level were the key parameters influencing variations in desorption of DDT in the three soils in similar experimental conditions. DDT dissolution in SDS and soil organic matter removal employing the ultrasonic-enhanced organic matter roll-up mechanism emerged as the two best possible methods of DDT desorption. The method offers a practical, potentially low-cost alternative to high volume, costly, hazardous solvent extraction of DDT.
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