System and method for selectively removing metals from industrial waste

Abstract

The invention generally relates to a system and method for selectively removing metals from a metal containing substance, and more particularly to a method and system for selectively extracting metals from fly ash with one or more of an acidic extraction process, basic extraction process, and supercritical carbon dioxide (scC02) and a co-solvent extraction process. Moreover, bi-products from an industrial process, e.g., coal fired plant, may be utilized in the extraction processes.

1 . A method of selectively extracting metals from a metal containing substance, comprising the steps of:
 providing the metal containing substance; and   simultaneously treating the metal containing substance with supercritical carbon dioxide (scCO 2 ) and a chelating agent (ligand) to selectively remove one or more metals from the metal containing substance.   
     
     
         2 . The method of  claim 1 , wherein the metal containing substance comprises a non-aqueous solid waste. 
     
     
         3 . The method of  claim 1 , wherein the metal containing substance one or more of an industrial waste, a fly ash waste, a soil, a fluorescent bulb waste, and an electrical component waste. 
     
     
         4 . The method of  claim 1 , wherein the metal containing substance comprises fly ash. 
     
     
         5 . The method of  claim 4 , further comprising the step of processing the fly ash to reduce a concentration of calcium in the fly ash prior to the simultaneously treating step. 
     
     
         6 . The method of  claim 5 , wherein the processing the fly ash to reduce a concentration step comprises
 processing the fly ash with a chelating agent to chelate calcium (Ca) from the fly ash to reduce the concentration of calcium to a first concentration.   
     
     
         7 . The method of  claim 6 , wherein the chelating agent is ethylenediaminetetraacetic acid (EDTA). 
     
     
         8 . The method of  claim 6 , wherein the resulting concentration is in parts per million (ppm). 
     
     
         9 . (canceled) 
     
     
         10 . The method of  claim 6 , wherein the simultaneously treating step comprises the steps of treating the fly ash with the supercritical carbon dioxide (scCO 2 ) and the chelating agent (ligand) in a supercritical fluid (SCF) extraction column at a first pressure and temperature for a first time to remove a predetermined metal from the metal containing substance. 
     
     
         11 . The method of  claim 10 , further comprising the step of treating the fly ash with the supercritical carbon dioxide (scCO 2 ) and a second chelating agent (ligand) in a supercritical fluid (SCF) extraction column at a second pressure and temperature for a second time to remove a predetermined metal from the one or more metals, wherein the second pressure and temperature is different than the first pressure and temperature and the second chelating agent (ligand) is different than the first chelating agent. 
     
     
         12 . The method of  claim 10 , wherein the chelating agent (ligand) is a selected group consisting of acetylacetone, hexafluoroacetylacetone, fluorinated crown ether, bis(2,4,4-trimethylphentyl)phosphinic acid, tributylphosphate, thenoyltrifluoroacetylacetone, lithium bis(trifluoroethyl)dithiocarbamate and combinations thereof. 
     
     
         13 .- 14 . (canceled) 
     
     
         15 . The method of claim  14 , wherein the one or more metals comprises rare earth metals comprising one or more of scandium, lanthanum, dysprosium, europium, neodymium, and yttrium. 
     
     
         16 .- 19 . (canceled) 
     
     
         20 . The method of  claim 1 , wherein the simultaneously treating the industrial waste step further comprises treating the industrial waste with one or more of a sulfuric acid (H 2 SO 4 ) and a nitric acid (HNO 3 ) to extract the one or more metals from the industrial waste. 
     
     
         21 . A method of selectively removing one or more metals from fly ash, comprising the steps of:
 providing the fly ash;   selectively removing a first metal from the fly ash with supercritical carbon dioxide (scCO 2 ) and a first chelating agent (ligand) at a first pressure and temperature in a supercritical fluid (SCF) extraction column;   selectively removing a second metal from the fly ash with supercritical carbon dioxide (scCO 2 ) and a second chelating agent (ligand) at a second pressure and temperature in the supercritical fluid (SCF) extraction column;   selectively removing a third metal from the fly ash with supercritical carbon dioxide (scCO 2 ) and a third chelating agent (ligand) at a third pressure and temperature in the supercritical fluid (SCF) extraction column;   selectively removing a fourth metal from the fly ash with supercritical carbon dioxide (scCO 2 ) and a fourth chelating agent (ligand) at a fourth pressure and temperature in the supercritical fluid (SCF) extraction column;   selectively removing a fifth metal from the fly ash with supercritical carbon dioxide (scCO 2 ) and a fifth chelating agent (ligand) at a fifth pressure and temperature in the supercritical fluid (SCF) extraction column; and   selectively removing a sixth metal from the fly ash with supercritical carbon dioxide (scCO 2 ) and a sixth chelating agent (ligand) at a sixth pressure and temperature in the supercritical fluid (SCF) extraction column.   
     
     
         22 . The method of  claim 21 , wherein the first chelating agent (ligand) is a mixture of thenoyltrifluoroacetylacetone (TFA) and methanol and the first metal is scandium. 
     
     
         23 . The method of  claim 22 , wherein the second chelating agent (ligand) is hexafluoroacetylacetone and the second metal includes lanthanum and neodymium. 
     
     
         24 . The method of  claim 23 , wherein the third chelating agent (ligand), the forth chelating agent (ligand), the fifth chelating agent (ligand) and the sixth chelating agent (ligand) are selected from the group consisting of acetylacetone, hexafluroacetylacetone, fluorinated crown ether, Bis(2,4,4-trimethylpentyl)phosphinic acid, tributylphosphate, thenoyltrifluoroacetylacetone, lithium bis(trifluoroethyl)dithiocarbamate and combinations of the same. 
     
     
         25 . A method of removing metals from industrial waste, comprising the steps of:
 providing the industrial waste from a fossil fuel-fired system, wherein the industrial waste comprises fly ash;   removing SO x  from a flue gas of the fossil fuel-fired system and processing the SO x  to form sulfuric acid (H 2 SO 4 );   removing NO x  from the flue gas of the fossil fuel-fired system and processing the NO x  to form nitric acid (HNO 3 );   removing CO 2  from the flue gas of the fossil fuel-fired system and processing the CO 2  to form supercritical carbon dioxide (scCO 2 );   extracting one or more metals from the industrial waste with one or more of the supercritical carbon dioxide (scCO 2 ), the nitric acid (HNO 3 ), the sulfuric acid (H 2 SO 4 ) and a chelating agent (ligand); and   selectively extracting one or more metals from the industrial waste with the supercritical carbon dioxide (scCO 2 ).   
     
     
         26 . The method of  claim 25 , wherein the chelating agent (ligand) is selected from the group consisting of acetylacetone, hexafluroacetylacetone, fluorinated crown ether, Bis(2,4,4-trimethylpentyl)phosphinic acid, tributylphosphate, thenoyltrifluoroacetylacetone, lithium bis(trifluoroethyl)dithiocarbamate and combinations of the same. 
     
     
         27 .- 29 . (canceled)