Patent ID: 6120579
Filing Date: 2000-09-19
Classification: B09C,C22B

Abstract:
A process for cleaning soils contaminated with mercury comprising:a. mixing the mercury-contaminated soils with a solid hypochlorite salt, producing a solid mixture;b. preparing a brine solution and mixing the brine solution with acid to adjust the pH, forming a liquid mixture;c. directing the solid mixture to a screw reactor;d. feeding the liquid mixture to the screw reactor in a direction countercurrent to the solid mixture;e. leaching the solid mixture with the liquid mixture, producing leached soils and a solution containing soluble compounds and fines;f. thickening the leached soils to separate the soils from the leaching solution;g. thickening the leached solution to separate the fines from the solution;h. combining the thickened soils and thickened fines to produce a soil matrix;i. rinsing the soil matrix with brine solution, water or both to recover any residual soluble mercury compounds and to produce a clean soil matrix;j. filtering the clean soil matrix to recover any solution held in the clean soil matrix;k. mixing the filtered solution with the thickened solutions from steps (f) and (g) to produce a resultant solution;l. treating the resultant solution with zinc powder or sulfide compound to produce clean brine and a mercury-zinc amalgam or a mercuric sulfide compound;m. recycling the clean brine back to the process; andn. recovering the mercury-zinc amalgam or the mercuric sulfide compound.