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Ultrasonic Enhanced Desorption of DDT from Contaminated Soils |
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| Authors: | Kandasamy Thangavadivel Mallavarapu Megharaj Roger St C Smart Peter J Lesniewski Darren Bates Ravi Naidu |
| Institution: | 1. Centre for Environmental Risk Assessment and Remediation (CERAR), University of South Australia, Mawson Lakes Campus, Mawson Lakes, South Australia, 5095, Australia 2. Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), Mawson Lakes Campus, Mawson Lakes, South Australia, 5095, Australia 3. Applied Centre for Structural and Synchrotron Studies, University of South Australia, Mawson Lakes Campus, Mawson Lakes, South Australia, 5095, Australia 4. Applied Physics, School of Electrical and Information Engineering, University of South Australia, Mawson Lakes Campus, Mawson Lakes, SA5095, Australia 5. Cavitus Pty Ltd., Research Laboratories, University of South Australia, Mawson Lakes Campus, Mawson Lakes, SA5095, Australia |
| Abstract: | 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?C8.4). The results were compared with DDT extracted using a strong solvent combination as reference. Slurry ranges from 5 to 20 wt.% were studied. For a soil slurry (10 wt.%) at pH 6.9 with 0.1% v/v SDS surfactant heated to 40°C for 30 min, desorption was above 80% in 30 s using 20 kHz, 932 W/L ultrasonic intensity without solvent extraction. Other soils gave lower desorption efficiency in the range 40?C60% after 30 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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