Methods and compositions for removing residues and substances from substrates using environmentally friendly solvents

Abstract

Environmentally friendly solvents used to dissolve or remove residues and/or substances from substrates wherein the residue and/or substance is contacted with a Generally Recognized As Safe solvent to dissolve the residue and/or substance in the solvent followed by the extraction of the residue and/or substance from the solvent such as by contact wiht carbon dioxide.

What is claimed is:  
     
         1 . A method of dissolving a petroleum-based substance, comprising: 
 introducing the petroleum-based substance to a reaction vessel;    contacting the petroleum-based substance with a carbon dioxide miscible solvent introduced to the reaction vessel;    dissolving at least a portion of the petroleum-based substance in the carbon dioxide miscible solvent contacting the petroleum-based substance;    removing a product from the reaction vessel, wherein the product comprises at least a portion of the petroleum-based substance dissolved in at least a portion of the solvent; and    contacting the product with carbon dioxide such that the petroleum-based substance is precipitated from the product.    
     
     
         2 . The method of  claim 1 , wherein the carbon dioxide miscible solvent is a GRAS (Generally Recognized As Safe) solvent.  
     
     
         3 . The method according to  claim 1 , wherein the petroleum residue comprises bitumen.  
     
     
         4 . The method of  claim 2 , wherein the GRAS solvent is a liquid benzoic acid ester-containing solvent.  
     
     
         5 . The method according to  claim 4 , wherein the benzoic acid ester-containing solvent has a flash pointer greater than about 98° C.  
     
     
         6 . The method according to  claim 4 , wherein the liquid benzoic acid ester-containing solvent is selected from the group consisting of methyl benzoic ester, ethyl benzoic acid ester, n-propyl benzoic acid ester, isobutyl benzoic acid ester, n-butyl benzoic acid ester, tert-butyl benzoic acid ester, isopropyl benzoic acid ester, isomers of petylpenzoate, and mixtures thereof.  
     
     
         7 . The method according to  claim 4 , wherein the benzoic acid ester-containing solvent is isopropylbenzoic acid ester.  
     
     
         8 . The method according to  claim 4 , wherein the benzoic acid ester-containing solvent comprises at least about 95 percent by weight of benzoic acid ester.  
     
     
         9 . The method according to  claim 1 , wherein the carbon dioxide comprises liquid carbon dioxide.  
     
     
         10 . The method according to  claim 1 , wherein the carbon dioxide comprises supercritical carbon dioxide.  
     
     
         11 . The method according to  claim 1 , wherein the carbon dioxide comprises gaseous carbon dioxide.  
     
     
         12 . The method according to  claim 1 , wherein the petroleum-based substance is present as an asphalt residue.  
     
     
         13 . The method according to  claim 1 , wherein the petroleum-based substance has a boiling point greater than about 150° C.  
     
     
         14 . The method according to  claim 1 , wherein the petroleum-based substance comprises asphaltene, and wherein said contacting step comprises removing from about 60 to 100 percent by weight of asphaltene based on the asphaltene present in the petroleum-based substance.  
     
     
         15 . The method according to  claim 1 , wherein the petroleum-based substance comprises bitumen and inorganic material, and wherein the inorganic material remains subsequent to said step of contacting the petroleum-based substance sample with benzoic acid ester containing solvent, said method further comprising contacting the inorganic material at least once with an organic solvent.  
     
     
         16 . The method according to  claim 15 , wherein the organic solvent is a C 1 -C 4  alcohol.  
     
     
         17 . The method according to  claim 16 , wherein the organic solvent is ethanol.  
     
     
         18 . A method for recovering bitumen, comprising: 
 contacting a substance containing bitumen with an ester-containing solvent;    dissolving at least a portion of the bitumen from the substance in the ester-containing solvent;    contacting the ester-containing solvent and dissolved bitumen with carbon dioxide to precipitate bitumen from the ester-containing solvent; and    recovering the precipitated bitumen.    
     
     
         19 . The method according to  claim 18 , wherein the ester-containing solvent has a flash pointer greater than about 98° C.  
     
     
         20 . The method according to  claim 19 , wherein the ester containing solvent is a benzoic acid ester selected from the group consisting of methyl benzoic ester, ethyl benzoic acid ester, n-propyl benzoic acid ester, isobutyl benzoic acid ester, n-butyl benzoic acid ester, tert-butyl benzoic acid ester, isopropyl benzoic acid ester, isomers of petylpenzoate, and mixtures thereof.  
     
     
         21 . The method according to  claim 20 , wherein the benzoic acid ester-containing solvent is isopropylbenzoic acid ester.  
     
     
         22 . The method according to  claim 20 , wherein the benzoic acid ester-containing solvent comprises at least about 95 percent by weight of benzoic acid ester.  
     
     
         23 . The method according to  claim 18 , wherein the carbon dioxide comprises liquid carbon dioxide.  
     
     
         24 . The method according to  claim 18 , wherein the carbon dioxide comprises supercritical carbon dioxide.  
     
     
         25 . The method according to  claim 18 , wherein the carbon dioxide comprises gaseous carbon dioxide.  
     
     
         26 . The method according to  claim 18 , wherein the substance containing bitumen has a boiling point greater than about 150° C.  
     
     
         27 . The method according to  claim 18 , wherein the substance containing bitumen comprises bitumen and inorganic material, and wherein the inorganic material remains subsequent to said step of contacting the substance with benzoic acid ester containing solvent, said method further comprising contacting the inorganic material at least once with an organic solvent.  
     
     
         28 . The method according to  claim 18 , wherein the ester-containing solvent is selected from the group consisting of salicylic acid esters, cinnamic acid esters, propionic acid esters, butyric acid esters, pentanoic acid esters, hexanoic acid esters, and mixtures thereof.  
     
     
         29 . The method according to  claim 28 , wherein the salicylic acid ester is selected from the group consisting of methyl salicylate, ethyl salicylate, n-propyl salicylate, isobutyl salicylate, n-butyl salicylate, tert-butyl salicylate, isomers of pentyl salicylate, isomers of hexyl salicylate, isomers of heptyl salicylate, isopropyl salicylate, and mixtures thereof.  
     
     
         30 . The method according to  claim 29 , wherein the salicylic acid ester-containing solvent is isopropyl salicylate.  
     
     
         31 . The method according to  claim 28 , wherein the ester-containing solvent comprises at least 95 percent by weight of salicylic acid ester.  
     
     
         32 . The method according to  claim 28 , wherein the cinnamic acid ester is selected from the group consisting of methyl cinnamate, ethyl cinnamate, n-propyl cinnamate, isobutyl cinnamate, n-butyl cinnamate, tert-butyl cinnamate, isomers of pentyl cinnamate, isomers of hexyl cinnamate, isomers of heptyl cinnamate, isopropyl cinnamate, benzyl cinnamate, and mixtures thereof.  
     
     
         33 . The method according to  claim 32 , wherein the cinnamic acid ester is isopropyl cinnamate.  
     
     
         34 . The method according to  claim 28 , wherein the ester-containing solvent comprises at least 95 percent by weight of cinnamic acid ester.  
     
     
         35 . The method according to  claim 28 , wherein the propionic acid ester is selected from the group consisting of phenyl propionate, benzyl propionate, hydroxyphenyl propionate, methyl phenyl propionate, isobutyl phenyl propionate, n-butyl phenyl propionate, tert-butyl phenyl propionate, isomers of pentyl phenyl propionate, isomers of hexyl phenyl propionate, isomers of heptyl phenyl propionate, isopropyl phenyl propionate, and mixtures thereof.  
     
     
         36 . The method according to  claim 35 , wherein the propionic acid ester is benzyl propionate.  
     
     
         37 . The method according to  claim 28 , wherein the ester-containing solvent comprises at least 95 percent by weight of propionic acid ester.  
     
     
         38 . The method according to  claim 28 , wherein the butyric acid ester is selected from the group consisting of phenyl butyrate, benzyl butyrate, hydroxyphenyl butyrate, methyl phenyl butyrate, isobutyl phenyl butyrate, n-butyl phenyl butyrate, tert-butyl phenyl butyrate, isomers of pentyl phenyl butyrate, isomers of hexyl phenyl butyrate, isomers of heptyl phenyl butyrate, isopropyl phenyl butyrate, and mixtures thereof.  
     
     
         39 . The method according to  claim 38 , wherein the butyric acid ester comprises benzyl butyrate.  
     
     
         40 . The method according to  claim 28 , wherein the ester-containing solvent comprises at least 95 percent by weight of butyric acid ester.  
     
     
         41 . The method according to  claim 28 , wherein the pentanoic acid 
 ester is selected from the group consisting of phenyl pentanoate, benzyl pentanoate, hydroxyphenyl pentanoate, methyl phenyl pentanoate, isobutyl phenyl pentanoate, n-butyl phenyl pentanoate, tert-butyl phenyl pentanoate, isomers of pentyl phenyl pentanoate, isomers of hexyl phenyl pentanoate, isomers of heptyl phenyl pentanoate, isopropyl phenyl pentanoate, and mixtures thereof.    
     
     
         42 . The method according to  claim 41 , wherein the pentanoic acid ester is benzyl pentanoate.  
     
     
         43 . The method according to  claim 28 , wherein the ester-containing solvent comprises at least 95 percent by weight of pentanoic acid ester.  
     
     
         44 . The method according to  claim 28 , wherein the hexanoic acid ester is selected from the group consisting of phenyl hexanoate, benzyl hexanoate, hydroxyphenyl hexanoate, methyl phenyl hexanoate, isobutyl phenyl hexanoate, n-butyl phenyl hexanoate, tert-butyl phenyl hexanoate, isomers of pentyl phenyl hexanoate, isomers of hexyl phenyl hexanoate, isomers of heptyl phenyl hexanoate, isopropyl phenyl hexanoate, and mixtures thereof.  
     
     
         45 . The method according to  claim 44 , wherein the hexanoic acid ester is benzyl hexanoate.  
     
     
         46 . The method according to  claim 28 , wherein the hexanoic acid ester comprises at least 95 percent by weight of hexanoic acid ester.  
     
     
         47 . The method according to  claim 28 , wherein the carbon dioxide comprises supercritical carbon dioxide.  
     
     
         48 . The method according to  claim 28 , wherein the carbon dioxide comprises gaseous carbon dioxide.  
     
     
         49 . The method according to  claim 28 , wherein the carbon dioxide comprises a mixture of at least two selected from the group consisting of liquid carbon dioxide, supercritical carbon dioxide, and gaseous carbon dioxide.  
     
     
         50 . A method of removing a substance from a substrate, comprising: 
 introducing the substrate having a desired substance for removal to a reaction vessel;    contacting the substrate with a GRAS solvent introduced to the reaction vessel;    dissolving at least a portion of the substance from the substrate in the GRAS solvent;    withdrawing at least a portion of the ester-containing solvent and dissolved portion of the substance from the reaction vessel as a product; and    contacting the product with carbon dioxide or a hydrocarbon gas to precipitate the substance from the product.    
     
     
         51 . The method of  claim 50 , wherein the GRAS solvent is a liquid benzoic acid ester-containing solvent.  
     
     
         52 . The method according to  claim 50 , wherein the benzoic acid ester-containing solvent has a flash pointer greater than about 98° C.  
     
     
         53 . The method according to  claim 52 , wherein the benzoic acid ester solvent is selected from the group consisting of methyl benzoic ester, ethyl benzoic acid ester, n-propyl benzoic acid ester, isobutyl benzoic acid ester, n-butyl benzoic acid ester, tert-butyl benzoic acid ester, isopropyl benzoic acid ester, isomers of petylpenzoate, and mixtures thereof.  
     
     
         54 . The method according to  claim 53 , wherein the benzoic acid ester-containing solvent is isopropylbenzoic acid ester.  
     
     
         55 . The method according to  claim 50 , wherein the benzoic acid ester-containing solvent comprises at least about 95 percent by weight of benzoic acid ester.  
     
     
         56 . The method according to  claim 50 , wherein the carbon dioxide comprises liquid carbon dioxide.  
     
     
         57 . The method according to  claim 50 , wherein the carbon dioxide comprises supercritical carbon dioxide.  
     
     
         58 . The method according to  claim 50 , wherein the carbon dioxide comprises gaseous carbon dioxide.  
     
     
         59 . The method according to  claim 50 , wherein the carbon dioxide comprises a mixture of at least two selected from the group consisting of liquid carbon dioxide, supercritical carbon dioxide, and gaseous carbon dioxide.  
     
     
         60 . The method according to  claim 50 , wherein the substance for removal is present as an asphalt residue and has a boiling point greater than about 150° C.  
     
     
         61 . The method according to  claim 50 , wherein the desired substance for removal comprises asphaltene, and wherein said contacting step comprises removing from about 60 to 100 percent by weight of asphaltene based on the asphaltene present in the petroleum residue.  
     
     
         62 . The method according to  claim 50 , wherein the desired substance for removal comprises bitumen and inorganic material, and wherein the inorganic material remains subsequent to said step of contacting the substance with benzoic acid ester containing solvent, said method further comprising contacting the inorganic material at least once with an organic solvent.  
     
     
         63 . The method according to  claim 62 , wherein the organic solvent is a C 1 -C 4  alcohol.  
     
     
         64 . The method according to  claim 63 , wherein the organic solvent is ethanol.  
     
     
         65 . The method according to  claim 50 , wherein the GRAS solvent is an ester-containing solvent is selected from the group consisting of salicylic acid esters, cinnamic acid esters, propionic acid esters, butyric acid esters, pentanoic acid esters, hexanoic acid esters, and mixtures thereof.  
     
     
         66 . The method according to  claim 65 , wherein the salicylic acid ester is selected from the group consisting of methyl salicylate, ethyl salicylate, n-propyl salicylate, isobutyl salicylate, n-butyl salicylate, tert-butyl salicylate, isomers of pentyl salicylate, isomers of hexyl salicylate, isomers of heptyl salicylate, isopropyl salicylate, and mixtures thereof.  
     
     
         67 . The method according to  claim 66 , wherein the salicylic acid ester-containing solvent is isopropyl salicylate.  
     
     
         68 . The method according to  claim 66 , wherein the ester-containing solvent comprises at least 95 percent by weight of salicylic acid ester.  
     
     
         69 . The method according to  claim 65 , wherein the cinnamic acid ester is selected from the group consisting of methyl cinnamate, ethyl cinnamate, n-propyl cinnamate, isobutyl cinnamate, n-butyl cinnamate, tert-butyl cinnamate, isomers of pentyl cinnamate, isomers of hexyl cinnamate, isomers of heptyl cinnamate, isopropyl cinnamate, benzyl cinnamate, and mixtures thereof.  
     
     
         70 . The method according to  claim 69 , wherein the cinnamic acid ester is isopropyl cinnamate.  
     
     
         71 . The method according to  claim 65 , wherein the ester-containing solvent comprises at least 95 percent by weight of cinnamic acid ester.  
     
     
         72 . The method according to  claim 65 , wherein the propionic acid ester is selected from the group consisting of phenyl propionate, benzyl propionate, hydroxyphenyl propionate, methyl phenyl propionate, isobutyl phenyl propionate, n-butyl phenyl propionate, tert-butyl phenyl propionate, isomers of pentyl phenyl propionate, isomers of hexyl phenyl propionate, isomers of heptyl phenyl propionate, isopropyl phenyl propionate, and mixtures thereof.  
     
     
         73 . The method according to  claim 72 , wherein the propionic acid ester is benzyl propionate.  
     
     
         74 . The method according to  claim 65 , wherein the ester-containing solvent comprises at least 95 percent by weight of propionic acid ester.  
     
     
         75 . The method according to  claim 65 , wherein the butyric acid ester is selected from the group consisting of phenyl butyrate, benzyl butyrate, hydroxyphenyl butyrate, methyl phenyl butyrate, isobutyl phenyl butyrate, n-butyl phenyl butyrate, tert-butyl phenyl butyrate, isomers of pentyl phenyl butyrate, isomers of hexyl phenyl butyrate, isomers of heptyl phenyl butyrate, isopropyl phenyl butyrate, and mixtures thereof.  
     
     
         76 . The method according to  claim 75 , wherein the butyric acid ester comprises benzyl butyrate.  
     
     
         77 . The method according to  claim 65 , wherein the ester-containing solvent comprises at least 95 percent by weight of butyric acid ester.  
     
     
         78 . The method according to  claim 65 , wherein the pentanoic acid ester is selected from the group consisting of phenyl pentanoate, benzyl pentanoate, hydroxyphenyl pentanoate, methyl phenyl pentanoate, isobutyl phenyl pentanoate, n-butyl phenyl pentanoate, tert-butyl phenyl pentanoate, isomers of pentyl phenyl pentanoate, isomers of hexyl phenyl pentanoate, isomers of heptyl phenyl pentanoate, isopropyl phenyl pentanoate, and mixtures thereof.  
     
     
         79 . The method according to  claim 78 , wherein the pentanoic acid ester is benzyl pentanoate.  
     
     
         80 . The method according to  claim 65 , wherein the ester-containing solvent comprises at least 95 percent by weight of pentanoic acid ester.  
     
     
         81 . The method according to  claim 65 , wherein the hexanoic acid ester is selected from the group consisting of phenyl hexanoate, benzyl hexanoate, hydroxyphenyl hexanoate, methyl phenyl hexanoate, isobutyl phenyl hexanoate, n-butyl phenyl hexanoate, tert-butyl phenyl hexanoate, isomers of pentyl phenyl hexanoate, isomers of hexyl phenyl hexanoate, isomers of heptyl phenyl hexanoate, isopropyl phenyl hexanoate, and mixtures thereof.  
     
     
         82 . The method according to  claim 81 , wherein the hexanoic acid ester is benzyl hexanoate.  
     
     
         83 . The method according to  claim 65 , wherein the hexanoic acid ester comprises at least 95 percent by weight of hexanoic acid ester.  
     
     
         84 . A method of dissolving a petroleum-based substance, comprising: 
 introducing the petroleum-based substance to a reaction vessel;    contacting the petroleum-based substance with an ester-containing solvent introduced to the reaction vessel;    dissolving at least a portion of the petroleum-based substance in the ester-containing solvent;    withdrawing at least a portion of the ester-containing solvent and dissolved portion of the petroleum-based substance from the reaction vessel as a product; and    precipitating the petroleum-based substance from the product.    
     
     
         85 . The method of  claim 93 , wherein the ester-containing solvent is a liquid benzoic acid ester-containing solvent.  
     
     
         86 . The method according to  claim 85 , wherein the benzoic acid ester-containing solvent has a flash pointer greater than about 98° C.  
     
     
         87 . The method according to  claim 85 , wherein the benzoic acid ester solvent is selected from the group consisting of methyl benzoic ester, ethyl benzoic acid ester, n-propyl benzoic acid ester, isobutyl benzoic acid ester, n-butyl benzoic acid ester, tert-butyl benzoic acid ester, isopropyl benzoic acid ester, isomers of petylpenzoate, and mixtures thereof.  
     
     
         88 . The method according to  claim 87 , wherein the benzoic acid ester-containing solvent is isopropylbenzoic acid ester.  
     
     
         89 . The method according to  claim 84 , wherein the benzoic acid ester-containing solvent comprises at least about 95 percent by weight of benzoic acid ester.  
     
     
         90 . The method according to  claim 84 , wherein the carbon dioxide comprises a mixture of at least two selected from the group consisting of liquid carbon dioxide, supercritical carbon dioxide, and gaseous carbon dioxide.  
     
     
         91 . The method according to  claim 84 , wherein the petroleum-based substance is present as an asphalt residue and has a boiling point greater than about 150° C.  
     
     
         92 . The method according to  claim 84 , wherein the petroleum-based substance comprises asphaltene, and wherein said contacting step comprises removing from about 60 to 100 percent by weight of asphaltene based on the asphaltene present in the petroleum-based substance.  
     
     
         93 . The method according to  claim 84 , wherein the petroleum-based substance comprises bitumen and inorganic material, and wherein the inorganic material remains subsequent to said step of contacting the petroleum residue sample with benzoic acid ester containing solvent, said method further comprising contacting the inorganic material at least once with an organic solvent.  
     
     
         94 . The method according to  claim 93 , wherein the organic solvent is a C 1 -C 4  alcohol.  
     
     
         95 . The method according to  claim 93 , wherein the organic solvent is ethanol.  
     
     
         96 . The method according to  claim 84 , wherein the ester-containing solvent has a flash point greater than about 98° C.  
     
     
         97 . The method according to  claim 84 , wherein the ester-containing solvent is selected from the group consisting of salicylic acid esters, cinnamic acid esters, propionic acid esters, butyric acid esters, pentanoic acid esters, hexanoic acid esters, and mixtures thereof.  
     
     
         98 . The method according to  claim 97 , wherein the salicylic acid ester is selected from the group consisting of methyl salicylate, ethyl salicylate, n-propyl salicylate, isobutyl salicylate, n-butyl salicylate, tert-butyl salicylate, isomers of pentyl salicylate, isomers of hexyl salicylate, isomers of heptyl salicylate, isopropyl salicylate, and mixtures thereof.  
     
     
         99 . The method according to  claim 101 , wherein the salicylic acid ester-containing solvent is isopropyl salicylate.  
     
     
         100 . The method according to  claim 97 , wherein the ester-containing solvent comprises at least 95 percent by weight of salicylic acid ester.  
     
     
         101 . The method according to  claim 97 , wherein the cinnamic acid ester is selected from the group consisting of methyl cinnamate, ethyl cinnamate, n-propyl cinnamate, isobutyl cinnamate, n-butyl cinnamate, tert-butyl cinnamate, isomers of pentyl cinnamate, isomers of hexyl cinnamate, isomers of heptyl cinnamate, isopropyl cinnamate, benzyl cinnamate, and mixtures thereof.  
     
     
         102 . The method according to  claim 101 , wherein the cinnamic acid ester is isopropyl cinnamate.  
     
     
         103 . The method according to  claim 97 , wherein the ester-containing solvent comprises at least 95 percent by weight of cinnamic acid ester.  
     
     
         104 . The method according to  claim 97 , wherein the propionic acid ester is selected from the group consisting of phenyl propionate, benzyl propionate, hydroxyphenyl propionate, methyl phenyl propionate, isobutyl phenyl propionate, n-butyl phenyl propionate, tert-butyl phenyl propionate, isomers of pentyl phenyl propionate, isomers of hexyl phenyl propionate, isomers of heptyl phenyl propionate, isopropyl phenyl propionate, and mixtures thereof.  
     
     
         105 . The method according to  claim 104 , wherein the propionic acid ester is benzyl propionate.  
     
     
         106 . The method according to  claim 97 , wherein the ester-containing solvent comprises at least 95 percent by weight of propionic acid ester.  
     
     
         107 . The method according to  claim 97 , wherein the butyric acid ester is selected from the group consisting of phenyl butyrate, benzyl butyrate, hydroxyphenyl butyrate, methyl phenyl butyrate, isobutyl phenyl butyrate, n-butyl phenyl butyrate, tert-butyl phenyl butyrate, isomers of pentyl phenyl butyrate, isomers of hexyl phenyl butyrate, isomers of heptyl phenyl butyrate, isopropyl phenyl butyrate, and mixtures thereof.  
     
     
         108 . The method according to  claim 107 , wherein the butyric acid ester comprises benzyl butyrate.  
     
     
         109 . The method according to  claim 97 , wherein the ester-containing solvent comprises at least 95 percent by weight of butyric acid ester.  
     
     
         110 . The method according to  claim 97 , wherein the pentanoic acid 
 ester is selected from the group consisting of phenyl pentanoate, benzyl pentanoate, hydroxyphenyl pentanoate, methyl phenyl pentanoate, isobutyl phenyl pentanoate, n-butyl phenyl pentanoate, tert-butyl phenyl pentanoate, isomers of pentyl phenyl pentanoate, isomers of hexyl phenyl pentanoate, isomers of heptyl phenyl pentanoate, isopropyl phenyl pentanoate, and mixtures thereof.    
     
     
         111 . The method according to  claim 110 , wherein the pentanoic acid ester is benzyl pentanoate.  
     
     
         112 . The method according to  claim 97 , wherein the ester-containing solvent comprises at least 95 percent by weight of pentanoic acid ester.  
     
     
         113 . The method according to  claim 97 , wherein the hexanoic acid ester is selected from the group consisting of phenyl hexanoate, benzyl hexanoate, hydroxyphenyl hexanoate, methyl phenyl hexanoate, isobutyl phenyl hexanoate, n-butyl phenyl hexanoate, tert-butyl phenyl hexanoate, isomers of pentyl phenyl hexanoate, isomers of hexyl phenyl hexanoate, isomers of heptyl phenyl hexanoate, isopropyl phenyl hexanoate, and mixtures thereof.  
     
     
         114 . The method according to  claim 113 , wherein the hexanoic acid ester is benzyl hexanoate.  
     
     
         115 . The method according to  claim 97 , wherein the hexanoic acid ester comprises at least 95 percent by weight of hexanoic acid ester.  
     
     
         116 . A method of dissolving a substance from an aqueous stream, comprising: 
 contacting an aqueous stream containing the substance with a water insoluble GRAS solvent;    dissolving at least a portion of the substance from the aqueous stream with the GRAS solvent; separating the GRAS solvent with dissolved substance from the aqueous stream; and    precipitating the substance from the GRAS solvent.    
     
     
         117 . A method according to  claim 116 , wherein the step of separating the GRAS solvent includes contacting with CO 2  or a hydrocarbon gas.