Influence of Wave-Absorbing Materials on the Heating Efficiency in Microwave Heating Treatment of Contaminated Soil

Abstract

China has a lot of wastelands that are usually overly contaminated as a result of the relocation of industrial enterprises. Given that long-term threats are thus generated, safe and effective treatment routines are urgently needed. Due to its low carbon footprint and environmental protection benefits, the microwave heating treatment of contaminated soil has generated substantial academic interest. Nevertheless, wave-absorbing materials must be added during the treatment process to holistically enhance the effectiveness of heating the contaminated soil. Therefore, this study selects three typical wave-absorbing materials, i.e., Fe3O4, SiC and activated carbon, to explore the influence of the addition of wave-absorbing materials on the microwave heating efficiency for contaminated soil. Moreover, the changes in the mineral phases and microscopic morphology of the contaminated soil and wave-absorbing materials after heating at different temperatures are analyzed. It is concluded that the heating rate would reach 39.5 °C/min when the amount of additive Fe3O4 reaches 8%; when the temperature exceeds 300 °C, the Fe3O4 will be gradually oxidized to Fe2O3. Activated carbon is a wave-absorbing material that has a higher thermal stability than Fe3O4, although it has less impact on the heating rate. The ability of SiC to absorb waves has a limited impact on the heating rate. During microwave heating, the microscopic morphology of the contaminated soil and wave-absorbing materials do not change significantly.