Method for eliminating heavy metals contained in sludge

Details Method for eliminating heavy metals contained in sludge Method for eliminating heavy metals contained in sludge

2006-11-28

2006-11-28

Johnson, Edward M. (Department: 1754)

Chemistry of inorganic compounds

Treating mixture to obtain metal containing compound

Iron group metal

Reexamination Certificate

active

07141225

ABSTRACT:
A method for purifying sludge suspected of containing heavy, toxic and/or precious metals in order to extract them, the sludge being suspended in an aqueous solution and together forming a mass to be treated. FeCl3is mixed with the mass, until an acidic pH of the solution is obtained. (CO2H)2and NH4Cl are then mixed with the mass until metal pro-chelates are formed. Mixed alkali sulfides are then mixed with the mass until a solution with a very basic pH is obtained, to form colloidal complex iron chelates, which trap the metals. The solution is neutralized by adding an acid, until alkaline-ferrous sulfides and hydroxides containing the metals are precipitated. The mass is then centrifuged to form from the mass a liquid phase and a solid phase, the solid phase containing the alkaline-ferrous sulfides.

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patent: 4428840 (1984-01-01), Mudder et al.
patent: 5665324 (1997-09-01), Izawa et al.
patent: 0 773 192 (1997-05-01), None

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