###### Abstract  
Soil pollution caused by oil leakage from various industrial facilities such as gas stations, oil plants, military bases, and railway depots has become a serious global environmental and geotechnical issue. The indirect-heated microwave thermal desorption technology has been developed in this study for economical and efficient remediation of oil or organic pollutants. The conclusions were made based on laboratory tests and analyses of the environmental (TPH; total petroleum hydrocarbons) and geotechnical (physical and mechanical) properties of the soil before and after treatments. (1) As the newly-developed equipment was operated for 3 h with the electric power of 32 kW to reach target temperature of 600 \({}^{\circ}\)C, more than 99.8% of TPH was removed. (2) In the aspect of geotechnical properties, the internal friction angle, maximum dry density and permeability coefficient of the soil were reduced by oil contamination and were finally restored to the almost initial level of the soil after treatment. Therefore, treated soil is expected to be reusable for geotechnical construction purposes such as construction fill materials. (3) It was also found that the developed technology reduces 75% of energy cost and 25% of CO\({}_{2}\) emissions for the remediation of lubricant oil-contaminated soil comparing with conventional one. microwave; treatment; thermal desorption; lubricant-contaminated soil; TPH (total petroleum hydrocarbons) +
Footnote †: journal: Applied Sciences  
Even though high-temperature thermal treatment such as thermal desorption is very effective to remediate the oil-contaminated soil, the thermal desorption method can change he texture and mineralogy of fine-grained soil [11]. In other words, the heating process causes dihydroxylation in its mineral structure and decomposition of its mineral structure at threshold temperatures above 400 \({}^{\circ}\)C [12], kaolinite deteriorates when heated between 420 \({}^{\circ}\)C and 500 \({}^{\circ}\)C [13] and the dehydroxylation of illites begins above 550 \({}^{\circ}\)C [11]. When it comes to the thermal desorption of fine-grained soil, following dihydroxylation in its mineral structure during the heating process, the effect of decomposition of its mineral structure on its geological function should be considered when designing the reuse of contaminated fine-grained soil. Thermal desorption technology, as one of the thermal treatment technologies, can remove more than 99% of volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), diesel, BTEX, gasoline and jet fuel [14], but as it uses fossil fuel, its remediation cost is high since energy efficiency is low, and it generates secondary emissions [15]. Furthermore, as the resource of fossil fuel is expected to be exhausted sooner or later, the development of alternative energy sources becomes more important. In this study, microwave instead of fossil fuel is considered as one of the alternative energies in the form of electrical energy. Soil remediation technology using microwave is expected to be the optimal method that enhances the energy efficiency for thermal desorption, and reduces the secondary emissions [16; 17]. Heating technology using microwave is based on the heating principle by molecular friction while polar materials such as water and iron contained in the material are rotating by changing the electromagnetic field [18]. [PERSON] et al. studied the remediation of contaminated soil based on microwave heating technology with advantages of rapid heating, uniform temperature distribution and high thermal efficiency [17]. Oil-contaminated soil remediation technology using microwave has been applied to the remediation of soil contaminated by organic matter and the disposal of sludge containing heavy metals. In particular, the microwave heating method is known to be effective for removing volatile or semi-volatile organic pollutants with polarity [19; 20; 21; 22].