## 1 Introduction  
Remediation technologies for soil remediation are broad classifications and are broadly divided into three types: biological, chemical, and physical methods [1]. The biological treatment method is a method of performing soil purification based on the mechanism of bio-degradation and bio-transformation of pollutants using soil microorganisms or plants [2]. Recently, it is one of the technologies receiving a lot of attention as the demand for environmentally friendly and sustainable development increases. However, it is also true that the biological treatment method requires a lot of time and labor and has a disadvantage in efficiency due to the actual physical and chemical treatment method [3]. Chemical treatment methods include methods such as chemical immobilization, fluid extraction, and oxidation. The chemical treatment method has relative advantages in terms of treatment time and labor input and also shows a higher pollutant removal efficiency than the biological treatment method in purification efficiency [1, 4]. However, the chemical treatment method has the disadvantage that the main purpose is to reduce the risk of pollutants, and it does not aim to completely remove the pollutants from the field [1]. Physical treatment methods include capping, cementitious waste forms, in-site vitrification, sorting, vapor stripping, and soil washing. Physical treatment techniques are treatment methods aimed at removing and isolating possible contaminants [5]. Similar to the chemical treatment method, it has many advantages in treatment time and efficiency but has the disadvantage of destroying the original soil function by causing a change in the biological quality of the soil [1; 5]. However, the soil washing technique combined with the physicochemical treatment method can suppress the aforementioned problems through the selection of a cleaning agent and change of the treatment process and has advantages compared to other methods in treatment efficiency and cost input [6]. In fact, the US Environmental Protection Agency (US EPA) states that the soil washing method costs $80-170 per ton of contaminated soil, which is less expensive than the chemical oxidation method ($130-390/ton) or the in-site vitrification method. In addition, the treatment time shows a relatively high treatment efficiency by treating about 2-4 tons of contaminated soil per hour [4]. Soil washing is a physical and chemical method that reduces the volume of pollutants by removing pollutants with an appropriate washing solution after excavating the soil and undergoing a pretreatment process to remove large substances or soil dumps [7]. Soil washing is used as a generic term for chemical extraction and soil washing, and the USEPA used water as a solvent and chemical extraction solution with additives such as surfactants and chelating agents [7; 8]. Thus, it is defined as a process for separating contaminants. That is, soil washing is a series of wet processes for removing pollutants from soil contaminated. A typical soil washing procedure consists of the following three steps: (1) chemical extraction, (2) particle separation, and (3) treatment after washing [4; 8; 9]. For a wide range of soil types and incoming pollutant concentrations, in some cases, remediation targets of less than 1 mg kg\({}^{-1}\) can be achieved [10]. The cost for waste separation and waste volume reduction is relatively low; hence, it can be used as a closed device, allowing the release of volatiles to be controlled. Additionally, it can be used as an effective pretreatment process for biological restoration [11]. However, contaminants are not destroyed and move to the washing solution and fine soil particles, so the washing solution and fine soil particles need secondary treatment or to be treated as hazardous waste, and the sludge generated during the wastewater treatment process must be treated. In addition, it is highly dependent on chemicals, and an additional pretreatment step is required when the organic content is high [4; 7; 12].