## 3 Results and Discussion
### Proposed Mechanisms of PCDD/F Soil Washing
#### 3.3.2 Bio-Surfactant Extraction  
[PERSON], [PERSON] and [PERSON] [26] compared four commercial solvents, e.g., ethanol, methanol, acetone, and Triton X-100, in removing dioxins from contaminated soil (initial TEQ value 10,000 ng-TEQ/kg) by only mechanical mixing (3000 rpm at room temperature) and concluded that ethanol washing resulted in the highest removal efficiency of 76% (soil: solvent ratio 10%, 10 min). Since that study, ethanol has been considered a very effective solvent for removing dioxins in soil. Ethanol was also used as a washing solvent in the study of [PERSON], [PERSON], [PERSON] and [PERSON] [27]. The authors washed dioxin-contaminated soil (9714 ng-TEQ/kg) and sediment (1208 ng-TEQ/kg) with ethanol 98% (3 g of soil/sediment with 12 mL of solvent, 200 rpm at room temperature). After five washes (24 hours per wash), the removal efficiencies were very positive, with 89% for soil and 72% for sediment. In another study of [PERSON] et al. (2010), ten washing times (20 g of soil 60 mL of washing solvent) were used with 75% ethanol at 60 \({}^{\circ}\)C, producing very high removal efficiencies (81% to 97%). In the current study, the removal efficiencies for sugarcane wine and pineapple wine were slightly lower than the three abovementioned studies, possibly due to the fewer washing cycles used,  
Figure 5: Effects of different physical mechanisms for the removal of PCDD/Fs from contaminated soil.  
the higher soil: solvent ratio, and the lower ethanol content of these two types of wine. Nevertheless, the idea of using naturally made solvents for soil decontamination is novel, and their benefits in the remediation in soil may outweigh their drawbacks [3; 17].  
It is reported that commercial ethanol can facilitate the transfer of the contaminants from the soil to the liquid. Its extraction is highly efficient and can be considered for field-scale applications. However, its weakness in this regard is its effect on the bioactivity of the soil. Bio-attenuation and cultivation of soil washed this way is restricted. Therefore, using wine, which has a high fermented alcoholic content, might reduce the possibility of this effect because it also produces a favorable environment for bacteria and fungi growth, which could further facilitate bioremediation methods (if necessary) and/or monitored natural attenuation. The composition of sugarcane wine and pineapple wine solvents was dominated by fermented ethanol in this study (Tables 1 and 2), and thus the relatively high removal efficiency seems understandable. Acidic compounds also affect the solubility of dioxins [37]. The other bio-surfactant compounds, including aldehyde, ketone, and ester, in the wine might also create good conditions for dioxins to be solubilized in the liquid solvent [1; 38]. Future studies will be needed to characterize the potential effects of limiting and enhancing the bioactivity and bio-toxicity of post-washed soil. In addition, the specific mechanisms underlying of wine's efficiency as a soil-washing solvent and the effects of the wine solvent on the physical and chemical properties of the washed soil also need to be elucidated. Yet, the preliminary results of this study suggest that naturally made solvents possess the ability to replace chemical solvents in washing highly contaminated soils.