Ion emplasement in soil with chim electrodes

• US 5,656,144 A
• Filed: 09/07/1995
• Issued: 08/12/1997
• Est. Priority Date: 12/20/1993
• Status: Expired due to Fees

• Current Assignee: Interior Department of United States As Represented By The Secretary of Interior
• Original Assignee: The United States of America as represented by the Secretary of the Interior
• Inventors: Hoover, Donald B., Leinz, Reinhard W.
• Primary Examiner(s): Tung, T.
• Application Number:
  US08/476,926
• Time in Patent Office: 705 Days
• Field of Search: 204/400, 204/435, 204/515-517, 205/687, 205/742, 205/771, 205/772, 205/746-750
• US Class Current: 204/515
• CPC Class Codes: B09C 1/08 chemically
• CPC Class Codes: B09C 1/085 electrochemically, e.g. by electrokinetics
• CPC Class Codes: B09C 2101/00 In situ

Abstract

An apparatus and method for soil remediation replaces specific ions in the soil electrochemically, using a DC voltage source and special multicompartment anodes and cathodes, each comprising an inner compartment containing electrolyte and a submerged electrode, a salt bridge connecting the electrolyte to an outer compartment containing a specific solution with replacement ions for soil remediation, and a membrane holding in the replacement solution. The membrane is put into contact with the soil, allowing electrical contact and ion migration while keeping the solution inside the anode or cathode. The multicompartment structure prevents the hydroxide and hydronium ion emplacement that causes acid and base fronts to form.

Claims

1. A method for introducing selected ions into a soil region without introducing either hydroxyl ions or hydronium ions comprising:

identifying in said soil region a soil cation to be replaced and a soil anion to be replaced;

introducing an anode comprising an inner compartment containing a first electrolyte, an electrode positioned in the inner compartment and at least partially submerged in the first electrolyte, an outer compartment, and a salt bridge separating the inner compartment from the outer compartment, said first electrolyte comprising an aqueous solution containing a replacement cation for said soil cation into said soil region;

introducing a cathode comprising an inner compartment containing a second electrolyte, an electrode positioned in the inner compartment and at least partially submerged in the second electrolyte, an outer compartment, and a salt bridge separating the inner compartment from the outer compartment, said second electrolyte comprising an aqueous solution containing a replacement anion for said soil anion into said soil region;

applying DC voltage across said anode and said cathode whereby said soil cation is replaced by said replacement cation and said soil anion is replaced by said replacement anion without the migration of hydroxide and hydronium ions into said soil region.

2. The method according to claim 1 wherein said anode comprises an anode membrane disposed between the aqueous solution containing said replacement cation and said soil region;

said cathode comprises a cathode membrane between the aqueous solution containing said replacement anion and said soil region.

3. The method according to claim 1 wherein the soil anion and soil cation are replaced by a member of the group consisting of a precipitated compound of the replacement cation and the soil anion, a precipitated compound of the replacement anion and the soil cation, and a combination of a precipitated compound of the replacement cation and the soil anion and a precipitated compound of the replacement anion and the soil cation.

4. The method according to claim 1 wherein the replacement anions migrating from the cathode replace the soil anions migrating into the anode, and the replacement cations migrating from the anode replace the soil cations migrating into the cathode.