The particles less than 4 mm are scrubbed with an attrition scrubber to break up agglomerates. The soil extractant mixture is continuously pumped out of the mixer to hydrocyclones that separate the solids and liquid. When the extraction is complete, the soils are rinsed with water to remove metals and acid. The extraction fluid and water are regenerated to remove metals and reform the acid. Heavy metals are concentrated for recovery.
Soils are mixed with lime to neutralize any residual acid.
No wastewater streams are generated. Under the Emerging Technology Program, a bench-scale system was tested using soils from 4 Superfund sites and a synthetic soil matrix.