A method for physically - chemical removal of toxic -, - a noble and / or heavy metal ions, from urban -, the case of industrial sludges or of liquid manure

摘要

The invention concerns a method for purifying sludge, suspected of containing toxic and/or precious heavy metals in view of the extraction, suspended in an aqueous solution and forming a mass to be treated. Said method consists in carrying out the following operations: mixing with the mass FeCl3 until an acid pH of the solution is obtained; mixing with the mass (CO2H) and NH4Cl until metallic pro-chelates are obtained; mixing the mass with mixed alkaline sulphides until a solution with a very basic pH is obtained, to form colloidal complex iron chelates, which trap said metals; neutralising the solution by adding an acid until alkaline-ferrous sulphides and hydroxides containing said metals are precipitated; forming by centrifuging, from the mass, a liquid phase and a solid phase containing said alkaline-ferrous sulphides.