Process for the removal of heavy metals from contaminants

A process for the treatment of a solid contaminant containing at least one heavy metal, which comprises:

• adding an immobilizing effective amount of metal scavenger to the solid contaminant and mixing said solid contaminant and said metal scavenger in the presence of water to immobilize the heavy metal, said metal scavenger comprising:
• a polyamine derivative formed from a polyamine having a molecular weight not higher than 500, said polyamine derivative containing, per molecule of said polyamine, at least one dithiocarboxyl group or a salt thereof as a N-substituting group substituted for an active hydrogen atom of said polyamine;
• and
• a polyethylene derivative formed from a polyethyleneimine having an average molecular weight of at least 5,000, said polyethylene derivative containing, per molecule of said polyethyleneimine, at least one dithiocarboxyl group substituted for an active hydrogen atom of said polyethyleneimine, wherein the mixing ratio of the polyamine derivative to the polyethyleneimine derivative is from about 9:1-7:3 by weight, and wherein from about 43% to about 99% of the substitutable active hydrogen atoms of the polyethyeleneimine and from about 56% to about 100% of the substitutable active hydrogen atoms of the polyamine are substituted by the dithiocarboxyl group.