Pilot-Scale Decontamination of Soil Polluted with As, Cr, Cu, PCP, and PCDDF by Attrition and Alkaline Leaching

Recently, an efficient and promising process was developed to allow the removal of As, Cr, Cu, pentachlorophenol (PCP), and polychlorodibenzo-dioxins and furans (PCDDF) from soil using alkaline leaching. The present study evaluates the performance and the robustness of this decontamination process for the treatment of four different polluted soils by attrition and alkaline leaching at a pilot scale. The attrition process carried out on the coarse fraction ($>0.125\mathrm{mm}$) allowed the removal of 24–42% of As, 0–13% of Cr, 23–46% of Cu, 0–85% of PCP, and 17–64% of PCDDF from the different contaminated soils. Removal yields of 87–95% of As, 50–72% of Cr, 73–84% of Cu, 52–100% of PCP, and 27–73% of PCDDF were obtained after three leaching steps ($[\mathrm{NaOH}]=1\mathrm{M}$; $[\text{Cocamydopropylbetaine}—\mathrm{BW}]=3\%$ (w/w); $t=2\mathrm{h}$; pulp density $[\mathrm{PD}]=10\%$ [w/v]) conducted on the fine fraction ($<0.125\mathrm{mm}$). The performance of both attrition and alkaline leaching processes seemed to be influenced by the nature of the soil and the type and initial level of contaminants present in the soils. However, the entire leaching process seemed to be highly efficient, allowing the simultaneous reduction of concentrations of inorganic and organic contaminants. The cost, including direct and indirect costs, were estimated between US$214 and 454 per ton of treated soil, depending on the nature of the soil and the initial level of contamination.