In-situ chemical oxidation-reduction and precipitation of heavy metals in soils and groundwater

A method for the in-situ treatment and remediation of an underground area contaminated with at least one member selected from the group consisting of hexavalent chromium and other heavy metals, semi-metals and cyanide comprising the steps of:

• (a) determining an effective amount and concentration of a first reactive solution comprising ferrous sulfate and an acid selected from the group consisting of sulfuric acid and phosphoric acid required to decomplex chromium and other heavy metals, semi-metals and cyanide from mineral surfaces, initiate reduction of hexavalent chromium to trivalent chromium and reduction of heavy metals and semi-metals to their least soluble valence state and to precipitate trivalent chromium, heavy metals and semi-metals as insoluble compounds;
• (b) determining an effective amount and concentration of a second reactive solution comprising hydrogen peroxide and an acid selected from the group consisting of sulfuric acid and phosphoric acid required to destroy organic ligands and enhance decomplexation;
• (c) injecting the first reactive solution and subsequently the second reactive solution at an effective pressure and at a flow rate in excess of a sustainable yield, the amount of said first reactive solution and second reactive solution into one or more injectors that are inserted into the ground, sealed and positioned so as to assure liquid flow and dispersion of the reactive solutions through the contaminated area;
• and
• (d) allowing said first and second reactive solutions to flow through the contaminated area thereby reacting chemically with the contaminants contained therein.