Removal of contaminants from materials

Abstract

An improved approach for cleaning and recycling materials is based on pressurized solvents including liquid propane, butane, dimethyl ether, and supercritical carbon dioxide. The apporaches are particularly suitable for cleaning sorbent materials. The approach allows for recycling of the sorbent materials, the solvent and the contaminents, typically oils and the like.

What is claimed is:  
     
         1 . A method of removing contaminants from highly porous material, said highly porous material in virgin form having an absorbency of at least about 25 percent by weight of said virgin porous material, said method comprising: 
 contacting said highly porous material in a pressure chamber with a pressurized solvent to form a solvent/contaminant mixture; and    recovering said highly porous material substantially free of said contaminants, wherein said recovered highly porous material has at least about 70 percent by weight of said contaminants removed.    
     
     
         2 . The method of  claim 1  wherein said highly porous material in virgin form has an absorbency greater than about 45 percent by weight of said virgin porous material.  
     
     
         3 . The method of  claim 1  wherein said highly porous material comprises a granular material.  
     
     
         4 . The method of  claim 3  wherein said granular material has an average diameter from about 0.1 mm to about 2 cm.  
     
     
         5 . The method of  claim 1  wherein said highly porous material comprises absorbent articles selected from the group consisting of a mats, pads, rags and booms.  
     
     
         6 . The method of  claim 1  further comprising agitating said solvent in said pressurized chamber.  
     
     
         7 . The method of  claim 1  wherein said agitation is performed by bubbling gas through said pressure chamber, by propelling a mechanical agitator, or by applying sonic energy.  
     
     
         8 . The method of  claim 1  wherein said highly porous material comprises a material selected from the group consisting of ball clay, common clay, shale, fire clay, Fuller's earth, kaolin, diatomaceous earth, montmorillonite, a natural fabric and a synthetic polymer.  
     
     
         9 . The method of  claim 1  wherein said recovered highly porous material has an absorptive capacity of at least about 50 percent by volume relative to the corresponding virgin material.  
     
     
         10 . The method of  claim 1  wherein said recovered highly porous material has at least 85 percent by weight of said contaminants removed.  
     
     
         11 . The method of  claim 1  wherein said contaminants comprise lubricants, petroleum oils, machine oils, dielectric oils, silicone oils, reflux residues, adhesive residues, plasticizers, fatty materials, waxy materials, or combinations thereof.  
     
     
         12 . The method of  claim 1  wherein said solvent comprises a pressurized fluid composition selected from the group consisting of carbon dioxide, propane, isobutane, butane, and dimethyl ether.  
     
     
         13 . The method of  claim 1  wherein said solvent further comprises a surfactant.  
     
     
         14 . The method of  claim 1  wherein said method further comprises separating said contaminants from said solvent.  
     
     
         15 . The method of  claim 1  said method further comprising: 
 heating said pressurized solvent/contaminant mixture to remove a first portion of said solvents from said pressurized solvent/contaminant mixture to produce a partially cleaned contaminant; and  
 reducing the pressure of said partially cleaned contaminant to remove substantially all of said solvent from said contaminant.  
 
     
     
         16 . A method of recovering a solvent from a pressurized solvent/contaminant mixture, said method comprising: 
 heating a contaminated pressurized solvent in a first vessel to remove a first portion of said solvent from said solvent/contaminant mixture to produce a partially cleaned contaminant;    reducing the pressure of said partially cleaned contaminant to remove substantially all of said solvent from said contaminant and volatile components of said contaminant to obtain a recovered contaminant substantially free of volatiles; and    separating said volatile components of said contaminant from said solvent.    
     
     
         17 . The method of  claim 16  wherein said partially cleaned contaminant is transferred to a second vessel to remove substantially all of said solvent.  
     
     
         18 . The method of  claim 16  wherein said volatile components are collected as a liquid in a separate vessel.  
     
     
         19 . The method of  claim 16  wherein said wherein said volatile components comprise gasoline.  
     
     
         20 . A method of removing contaminants from porous materials, said method comprising: 
 contacting a quantity of porous material in a pressurized chamber with a pressurized solvent to form a solvent/contaminant mixture that is removed from said pressurized chamber; and    flowing said removed solvent/contaminant mixture through a cosolvent chamber with contaminated porous material to remove contaminants from said contaminated porous material.    
     
     
         21 . The method of  claim 20  further comprising flowing clean solvent through said cosolvent chamber after completing said flow of solvent/contaminant mixture through said cosolvent chamber.  
     
     
         22 . The method of  claim 20  wherein said pressurized chamber and said cosolvent chamber comprise the same vessel.  
     
     
         23 . An apparatus for removing organic materials from a porous material comprising: 
 a pressure chamber; and    a conduit in fluid communication with an outflow of said pressure chamber and an inflow of a cosolvent chamber such that outflow of said pressure chamber can be circulated through said cosolvent chamber.    
     
     
         24 . The apparatus of  claim 23  wherein said conduit comprises a surge tank such that said outflow can be stored for circulation in said cosolvent chamber.  
     
     
         25 . The apparatus of  claim 23  wherein said pressure chamber and said cosolvent chamber comprise the same vessel.  
     
     
         26 . The apparatus of  claim 23  wherein said pressure chamber and said cosolvent chamber comprise different vessels.  
     
     
         27 . A method of removing polar and nonpolar contaminants from an article, said method comprising contacting said contaminated article with pressurized dimethyl ether such that said article after completion of said contacting step has at least about 70 percent each of said polar contaminants and said nonpolar contaminants removed.  
     
     
         28 . The method of  claim 27  wherein said article after completion of said contacting step has at least about 85 percent each of said polar contaminants and said nonpolar contaminants removed.  
     
     
         29 . A method of separating dimethyl ether from polar and nonpolar contaminants, said method comprising: 
 heating said contaminated dimethyl ether in a first vessel to remove a first portion of said solvent from said dimethyl ether/contaminant mixture to produce a partially cleaned contaminant;    reducing the pressure of said partially cleaned contaminant to remove substantially all of said dimethyl ether from said contaminant; and    decanting said polar component of said contaminant from said nonpolar component of said contaminant.    
     
     
         30 . A method of cleaning sorbent articles comprising applying sonic energy to agitate a pressurized solvent in contact with said sorbent article in a pressurized vessel, said pressurized solvent comprising a surfactant.