US 5,326,439 AGranted

In-situ chromate reduction and heavy metal immobilization

AssigneeAndco Environmental Processes, Inc.

InventorMichael D. Brewster

Life of this patent

Estimating the term…

Loading patent…

Abstract

A process for removing heavy metal contaminants from groundwater without injecting anion contaminants thereinto and without providing surface sludge for disposal is described. The process consists of withdrawing a flow of groundwater containing the contaminants and passing the flow of groundwater through an electrochemical cell having at least an anion of iron or an iron containing alloy wherein the cell consists of an anode, a cathode, and a plurality of closely spaced additional electrodes disposed therebetween. The cell then generates ferrous ion and hydroxyl ions into the solution which is then reinjected upstream of the flow. In-situ then hexavalent chromium will be reduced to nontoxic trivalent chromium and will form an insoluble iron containing compound or complex with the hydroxide to immobilize the chromium in-situ. Other heavy metal contaminants similarly will be immobilized by reacting with the iron, or through the absorbent properties of a ferrous iron hydroxide generated.

Claims5

Dependent claims

A method for removing hexavalent chromium contaminants from groundwater along with any heavy metal ions which are capable of forming an insoluble iron compound or complex comprising the steps of:

providing an electrochemical cell comprising a pair of outer electrode elements which are, respectively, an anode and a cathode, positioned in a parallel spaced apart relationship and a plurality of additional electrode elements disposed between said outer electrode elements in a closely spaced relationship therewith, said additional elements being substantially equidistantly spaced, one from another, and disposed parallel to said outer electrodes;
locating said cell in proximity to a flow of groundwater containing hexavalent chromium ions or said other heavy metal ions and removing a portion of said groundwater flow and directing it through said electrochemical cell while passing an electric current through the cell between the anode and cathode so as to anodically produce ferrous ions while cathodically producing hydroxide ions said ferrous ions being entrained in said flow;
and injecting the flow of water from between said electrodes containing unreacted ferrous ions into said groundwater upstream of where said portion was removed.

Dependencies are inferred from the claim text.