Configurations and Methods of Electrochemical Lead Recovery from Contaminated Soil

Abstract

A soil remediation system includes an electrochemical cell that is configured to provide increased mass transfer and a decreased diffusion layer between the electrodes to thereby allow formation of a homogenous lead deposit that is substantially free of dendrite formation and easily removed.

1 - 26 . (canceled) 
     
     
         27 . A method of operating an electrolytic cell, comprising:
 positioning a separator between an anode surface of an anode and a cathode surface of a cathode in an electrolyzer such that a flow path for an electrolyte through a cathode compartment is formed;   providing the electrolyte to the cathode compartment, wherein the electrolyte comprises a metal that is optionally in complex with a complexing agent;   positioning the separator and the cathode surface such that the electrolyte can be pumped through the cathode compartment at a predetermined flow velocity that provides a Reynolds number of at least 2000; and   pumping the electrolyte through the cathode compartment at a rate that is at least the predetermined velocity along the flow path, and while pumping the electrolyte at the rate, applying a potential to the cathode in an amount effective to allow deposition of the metal onto the cathode surface as a smooth film at non-current limiting conditions.   
     
     
         28 . The method of  claim 27 , wherein the metal is present at a concentration of below 5000 ppm. 
     
     
         29 . The method of  claim 27 , wherein the potential is selected such that current density in the flow path is proportional to a concentration of the metal concentration and the Reynolds number. 
     
     
         30 . The method of  claim 27 , wherein the flow path is an upward flow path through the cathode compartment. 
     
     
         31 . The method of  claim 27 , wherein the flow path designed such that at least 80 vol % of the electrolyte in the cathode compartment pass between the cathode surface. 
     
     
         32 . The method of  claim 27 , wherein the step of pumping comprises recirculating the electrolyte through the cathode compartment. 
     
     
         33 . The method of  claim 27 , wherein the electrolyzer comprises at least one of a jet, a protrusion, and a funnel that is configured to induce or increase turbulent flow of the electrolyte. 
     
     
         34 . The method of  claim 27 , further comprising a step of operating the electrolyzer under current limiting conditions. 
     
     
         35 . The method of  claim 27 , wherein the cathode comprises a carbon felt electrode. 
     
     
         36 . The method of  claim 35 , wherein the flow path is configured such that the electrolyte flows through the carbon felt electrode. 
     
     
         37 . The method of  claim 36 , wherein the flow path is configured such that the electrolyte first flows between the cathode surface and the separator, then flows through the cathode, and then leaves the cathode compartment. 
     
     
         38 . The method of  claim 37 , wherein the electrolyte is recirculated to the cathode compartment. 
     
     
         39 . A method of operating an electrolytic cell comprising:
 positioning an anode and a cathode in an electrolyzer, wherein the cathode is in electrical contact with an electrolyte that includes a metal at a concentration of less than 5000 ppm, wherein the metal is optionally in complex with a complexing agent; and   pumping the electrolyte along a flow path between the anode and the cathode at a flow velocity and cathode potential at which the metal is plated onto the cathode in form of a smooth film under non-current limiting conditions.   
     
     
         40 . The method of  claim 39  further comprising pumping the electrolyte at a second flow velocity that is greater than the flow velocity, wherein the metal is plated onto the cathode at the second flow velocity in a form other than the smooth film. 
     
     
         41 . The method of  claim 40  wherein the form other than the smooth film is a powdery deposit or a dendritic form. 
     
     
         42 . The method of  claim 39  wherein the metal is present in the electrolyte at a concentration of less than 500 ppm. 
     
     
         43 . The method of  claim 39  wherein the electrolyte is recirculated, and wherein the metal is selected from the group consisting of copper, lead, and zinc. 
     
     
         44 . The method of  claim 39  wherein the cathode comprises a carbon felt electrode. 
     
     
         45 . The method of  claim 44  the flow path is configured such that the electrolyte flows through the carbon felt electrode. 
     
     
         46 . The method of  claim 45  wherein the flow path is configured such that the electrolyte first flows between the cathode surface and the separator, then flows through the cathode, and then leaves the cathode compartment.