Electrochemical Concentration of Lanthanide and Actinide Elements

Abstract

A carbon paste electrode is modified with a chemical agent that is selective for a plurality of lanthanides and actinides (f-series) elements. The modified carbon paste electrode selectively has different voltages applied thereto where a first voltage is used to cause the deposition of one or more lanthanides or actinides from an industrial or environmental sample onto the electrode, and, subsequent to removal of the electrode from the sample and insertion into a second sample where concentration of lanthanides or actinides is preferred, a second voltage is used to cause the deposited lanthanides and/or actinides to be discharged from the electrode for concentration into the second sample.

1 . A modified carbon paste electrode, comprising:
 an electrically conductive substrate;   a carbon paste adhered to a surface of said substrate; and   one or more modifying agents dispersed within said carbon paste, wherein at least one of said modifying agents selectively binds to a plurality of lanthanide and actinide elements.   
     
     
         2 . The modified carbon paste electrode of  claim 1  wherein said one or more modifying agents include a plurality of modifying agents. 
     
     
         3 . The modified carbon paste electrode of  claim 1  wherein said carbon paste comprises a binder and a conductive component, and wherein said at least one modifying agent and said conductive component are uniformly dispersed in said binder. 
     
     
         4 . The modified carbon paste electrode of  claim 3  wherein said binder is selected from the group consisting of mineral (paraffin) oils, aliphatic and aromatic hydrocarbons, and silicone oils, greases, and rubbers. 
     
     
         5 . The modified carbon paste electrode of  claim 1  wherein said substrate includes a conductive element and an insulative housing. 
     
     
         6 . The modified carbon paste electrode of  claim 5  wherein said insulative housing is made from a material selected from glasses, ceramics, polyethylene, crosslinked polyethylene, polyvinyl chloride (PVC), Kapton, rubber-like polymers, oil impregnated paper, Teflon, silicone, and modified ethylene tetrafluoroethylene (ETFE). 
     
     
         7 . The modified carbon paste electrode of  claim 5  wherein said conductive element is made from platinum, gold, silver, glassy carbon, brass, copper, graphite, porous graphite, molybdenum, and combinations thereof. 
     
     
         8 . The modified carbon paste electrode of  claim 1  wherein the at least one modifying agent is selected from the group consisting of 1,2-dihydroxybenzene-3,5-disulfonic acid, 2-hydroxyisobutyric acid, trimetaphosphoric acid, trans-1,2-cyclohexylenedinitrilotetraacetic acid, 2-hydroxy-2-methylpropanoic acid, iminodiacetic acid, nitrilotriacetic acid, ethylenedinitrilotetraacetic acid, diethylenetriamine-pentacetic acid, 2,2′,2″, 2′″-(1,4,7,10tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid, N-(2-carboxyphenyl)iminodiacetic acid, dihydroxycyclobutenedione, 3,6,9,12-tetrakis(carboxymethyl)-3,6,9,12-tetraazatetradecane-1,14-dioic acid and derivatives of these compounds. 
     
     
         9 . A retrieving and depositing method for retrieving one or more lanthanides or actinides from a first solution and depositing said one or more lanthanides or actinides in a second solution, comprising the steps of
 contacting a first solution which contains one or more lanthanides or actinides with a modified carbon paste electrode comprised of an electrically conductive substrate with a carbon paste adhered to a surfaces of said substrate and with one or modifying agents that selectively bind lanthanides or actinides dispersed within said carbon paste;   applying a first voltage to the modified carbon paste electrode suitable to deposit said one or more lanthanides or actinides contained in said sample onto the modified carbon paste electrode;   moving the modified carbon paste electrode to a second solution; and   applying a second voltage suitable to release of said one or more lanthanides or actinides into said second sample.   
     
     
         10 . The method of  claim 9  wherein said first solution is an environmental sample. 
     
     
         11 . The method of  claim 9  wherein said first solution is an industrial sample. 
     
     
         12 . The method of  claim 9  wherein said second solution is of a smaller volume than said first solution, wherein said steps of contacting, applying, moving, and applying concentrate said one or more lanthanides or actinides in said second solution. 
     
     
         13 . The method of  claim 9  wherein the modified paste electrode is repeatedly cycled between the first solution and said second solution, and said step of applying the first voltage is performed within the first solution and said step of applying the second voltage is performed within the second solution. 
     
     
         14 . The method of  claim 9  wherein said chemical agent is selected from the group consisting of 1,2-dihydroxybenzene-3,5-disulfonic acid, 2-hydroxyisobutyric acid, trimetaphosphoric acid, trans-1,2-cyclohexylenedinitrilotetraacetic acid, 2-hydroxy-2-methylpropanoic acid, iminodiacetic acid, nitrilotriacetic acid, ethylenedinitrilotetraacetic acid, diethylenetriamine-pentacetic acid, 2,2′,2″,2″-(1,4,7,10tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid, N-(2-carboxyphenyl)iminodiacetic acid, dihydroxycyclobutenedione, 3,6,9,12-tetrakis(carboxymethyl)-3,6,9,12-tetraazatetradecane-1,14-dioic acid and derivatives of these compounds. 
     
     
         15 . The method of  claim 14  wherein said chemical agent is reduced by said step of applying said first voltage and wherein said chemical agent is in a ground state by said step of applying said second voltage. 
     
     
         16 . The method of  claim 9  wherein the first voltage ranges from −0.05 to −0.05 V and wherein the second voltage ranges from 0.1 to 0.09 V.