Study on the remediation of organic soil contaminated with polychlorinated biphenyls using a variable frequency microwave furnace

The development of new and innovative remediation technologies for soil contaminated with Polychlorinated Biphenyl (PCB) is necessary to fulfill the need of cleanup of contaminated sites. In the past eight years the Laboratory for Microwave treatment as Hazardous Substance Management Research Center has investigated the use of Microwave energy to remediate contaminated soils. A major drawback of using single frequencies of the microwave range is the non-uniformity of the electromagnetic field. In this thesis a Variable Frequency Microwave Furnace (operating between 2.40 and 7.50 GHz) is used to improve the uniformity of the field. A new method is used to map the field uniformity in a fixed and variable frequency furnace. Frequency ranges larger than 1 GHz lead to uniform field distribution. Soil with an organic content of 82% was contaminated with PCB congeners #53 and #65 to ca. 400 ppm, and subjected to microwave exposure. Extracts of blanks and treated samples were analyzed with GC/MS. No breakdown products were observed in any of the extracts. The reduction of PCB in the extract was not dependent on the length of exposure to microwave energy. Soil temperature had the greatest effect on the reduction efficiency in the extract: the reduction efficiency at 170°C averaged at 55%, at 100°C it was only 17% for PCB #53. In preliminary experiments no PCBs were detected in the offgas. Additional experiments have to investigate the fate of the PCB in the soil as the offgas