Supercritical fluid extraction of chlorinated pesticide from soils | |
| Author | Jantanee Ongartharn |
| Call Number | AIT Thesis no.EV-99-27 |
| Subject(s) | Soils--Pesticide content Pesticides--Environmental aspects |
| Note | A thesis submitted in partial fulfillment of the requirement for the degree of Master of Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | Supercritical carbon dioxide was used to extract a.-endosulfan from three spiked topsoils (sandy, clay loam, and clay) in Thailand. Firstly, the study was carried out to investigate the effect of varying SFE conditions on the recovery of a.-endosulfan from all spiked topsoils. The following SFE parameters were varied to determine their influence on recovery of a.-endosulfan; (1) density and pressure at constant temperature; (2) temperature at constant density; (3) addition of polar methanol modifier to carbon dioxide; and ( 4) dynamic extraction time. The a.-endosulfan recoveries were shown to increase with increases in density (0.25-0.80 g/ml) and pressure (77-163 atm.). Temperature increased in range 40-60 °C, however, was found to have little effect on a.-endosulfan recoveries. The addition of polar methanol modifier at 3-5% highly increased the yield of a.-endosulfan. The competitive interactions between the modifier, supercritical fluid and the target analyte with the sorptive sites on the bulk matrix are poorly understood. However, at 7% modifier there was limitation of solubility of methanol in fluid. For kinetic study, the dynamic extraction time was varied from 10-50 min., and the recovery yield increased with increases in time. The SFE optimum conditions of density, temperature, modifier, and dynamic extraction time were identified and presented. The extraction yield depends on the interaction of a.-endosulfan, soil matrix, and supercritical fluid characteristics which is not clearly understood. From this study, it was found that clay matrix with higher content of organic matter, oxides of Fe, Mn, and Al and smaller particle size had greater affinity to absorb a.-endosulfan more strongly than clay loam and sand matrices. Secondly, the a.-endosulfan from three spiked topsoils was extracted with optimum SFE conditions identified. The study was conducted to demonstrate the effect of soil pH, moisture content, and contaminated concentration on a.-endosulfan recovery. The pH at acidic (~2) and alkaline (~ 12) conditions was found to have a little effect on the recovery of a.- endosulfan. The possible reasons were also discussed. In the case of the soil moisture content, 5-10% moisture content in soil increased the yield of a.-endosulfan. The moisture content within the soil may have an effect on the equilibrium distribution of a.-endosulfan between solid and fluid phase and thus affect the rate of extraction. However, at 25% moisture content there was the limitation of solubility of water in fluid. The extraction of 1 ng/g a.-endosulfan from all spiked topsoils gave lower yield than the extraction from 100 ng/g a.-endosulfan due to the strength of holding capacity of soil to a.-endosulfan. Thirdly, a comparison between SFE and soxhlet extraction was studied. The SFE technique was found to be better than the soxhlet extraction technique in term of the recovery yield, impurity, solvent consumption and toxic waste problem, health and accidental risk, cost, and time and labor intensity. |
| Year | 1999 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Ozaki, Hiroaki; |
| Examination Committee(s) | Preeda Parkpian ;Apisit Eiumnoh ; |
| Scholarship Donor(s) | Royal Thai Government ; |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 1999 |