Document Type
Thesis
Date of Award
12-31-1990
Degree Name
Master of Science in Environmental Science - (M.S.)
Department
Chemical Engineering, Chemistry and Environmental Science
First Advisor
Leonard Dauerman
Second Advisor
Richard B. Trattner
Third Advisor
Barbara B. Kebbekus
Abstract
Microwave treatment of hazardous wastes was studied on both bench-scale and pilot plant scales. Bench-scale studies were carried out on two processes: steam distillation to effect the removal of volatile and semi-volatile organics from substrata like soil; immobilization of heavy metals like chromium in soil.
The pilot plant work involved the start-up of a newly-installed facility and the determination of the efficiency of energy transfer from the power system to a load.
It was found that microwave generated steam within the substratum effects the distillation of naphthalene in both sandy soil and clay soil, respectively; 95% removal is effected within the range of temperatures corresponding to steam distillation. The mechanism for the removal of the remaining 5% is less certain. At about 220°C to 225°C, the naphthalene removal is greater than 99% from both the sandy soil and the clay soil. It is possible that bound water distills at these elevated temperatures removing the naphthalene. But it may also be possible that the naphthalene directly volatilizes especially from clay soil at elevated temperatures.
With respect to the bench-scale studies on the microwave process for the immobilization of chromium in soil, unlike previous studies, this was a study to compare the effects of microwave and thermal heating of chromium-contaminated soil. The soil was impregnated to approximately the 80,000 ppm level.
It was found that within the particle range specified for testing the leachability of hazardous wastes under EP Toxicity Test Protocol adopted to meet the requirements of the federal Resource Conservation and Recovery Act (RCRA), the leachability of the microwave treated soil was approximately 20-fold less than thermally treated soil, in the 5-6 ppm range. On the one hand, the leachability of soil particles of decreasing size, below the range specified in the aforestated protocol, increased many-fold for the microwave treated soil. On the other hand, there was little change for the thermal treated soil. It is concluded that the mechanism for the immobilization of chromium in soil is different for microwave and thermal treatments. It is theorized that in microwave treatment, microwave absorbing materials, like hematite, heat up rapidly, thermal equilibrium is not reached, diffusion of the absorber or adjacent material occurs, and causes encapsulation of chromium-impregnated soil. In contrast, during thermal treatment, each portion of the soil is subject to the same treatment and thus the property of leachability does not depend on particle size; further, the thermal process is limited: the leachability of microwave treated soil is much less than in thermally treated soil under the protocol conditions.
It is concluded that this pilot plant is safe to operate with respect to radiation hazards. The emission of the radiations is always below 2 MW/cm2 during the experiments of the measurement. A relatively high efficiency, approximately 70%, was found for the transfer of energy from the power source, the magnetrons, to the load.
Recommended Citation
He, Yaoli, "Microwave treatment of hazardous wastes : benchscale and pilot plant studies" (1990). Theses. 2714.
https://digitalcommons.njit.edu/theses/2714
