Environmental-economical assessment of the use of ultrasonication for pre-treatment of the soils contaminated by phenanthrene

Removing aromatic contaminants from the soil using ultrasonic waves is a new technology with the potential for practical use in industrial scale. In this study, the ultrasonication technology was presumed as a pre-treatment for soils contaminated with phenanthrene. Since the removal of this contaminant from the soil by ultrasonication reduces the cost of treatments such as soil washing, the optimization of independent variables has been investigated in the present study. Effect of variables such as phenanthrene primary concentration (7.5-517.5 mg/kg), ultrasonic power (0-395 W), the volume of water (0-400 mL) and the overall retention time (0-1 h) on the cost-saving of treatment for 100 g soil samples has been presented. The Response Surface Methodology has been used for modeling the results of this research. Based on the results of this research, the optimal conditions have been proposed for maximization of the cost-savings by ultrasonication and minimization of the ultrasonication operating costs. The best proposed conditions to achieve the maximum pollutant removal occurred in soil pretreatments using ultrasonication in water volume of 300 mL, the ultrasonic power of 139W, and 0.5 h process duration, which led to saving of 1.42 (sic)/100 g soil for the replacement of the soil washing by the ultrasonication process.