THERMAL TREATMENT WITH THE APPLICATION OF NANO SCALE TECHNOLOGY

摘要

Nanoscale iron particles represent a new generation of environmental remediation technologies that could provide cost-effective solutions to some of the most challenging environmental cleanup problems when applied with thermal treatment. A feasibility study was conducted to find the effectiveness of nano-particles to treat PCB contaminated soil when combined with thermal treatment. Ten samples each of soil and filter cake samples were used from a confidential site with PCB contamination. Soil and filter cake samples were mixed with iron nano-particles and subject to thermal treatment in the presence and absence of oxygen. Thermal treatment in presence of oxygen was conducted at 300°C and in the absence of oxygen at three different temperatures 200, 300 and 400 °C. The exhaust gases from thermal treatment were collected using an Amberlite XAD trap. Both treated soil and XAD trap were extracted separately by Soxhlet extraction and were then analyzed for PCBs using GC/MS. Separate experiments were conducted to test the destruction efficiencies with only thermal treatment. Destruction efficiencies when soil and filter cake samples were mixed with nano-iron particles and subject to thermal treatment in the absence of air ranged from 70%-76%, 85%-89% and 89% -95% at 200 °C, 300 °C and 400 °C respectively. Destruction efficiencies in presence of air at 300 °C were between 95-99%. These efficiencies were higher (25 - 40%) when compared to soil subject to only thermal treatment. The destruction of PCB increases in the following order: soil subject to thermal treatment, soil treated with nano-particles in absence of air and soil treated with nano-partcles in presence of air. The iron nano-particles were able to reduce PCB concentrations in both the mixing and thermal steps. The results of this study also showed that soil structure, pollutant loading, temperature, and reaction atmosphere all have an impact on PCB destruction.