Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
2001-05-17
2003-04-08
Fortuna, Ana (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S651000, C210S653000, C210S502100, C210S490000, C210S198200, C428S475500, C427S245000
Reexamination Certificate
active
06544422
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to ion-binding ligands covalently bonded to membranes and to a process for removing and concentrating certain selected ions from solutions using the ligand-membrane compositions, wherein such ions may be admixed with other ions present in much higher concentrations. More particularly, the invention relates to ligand-membrane compositions and to a process for removing such ions from an admixture with other ions in a source solution by forming a complex of the selected ions with the ligand-membrane compositions by flowing such solutions through a contacting device containing the ligand-membrane compositions and then breaking the complex of the selected ion from the composition to which such ion has become attached by flowing a receiving liquid in much smaller volume than the volume of solution passed through the contacting device to remove and concentrate the selected ions in solution in the receiving liquid. The concentrated ions thus removed may then be recovered by known methods.
BACKGROUND OF THE INVENTION
Composite membranes of the type utilized in one embodiment of the present invention have been previously described in U.S. Pat. No. 4,618,533 to Steuck. Some of the ion-binding ligands of the types disclosed herein are also known. For example, U.S. Pat. No. 4,952,321 to Bradshaw et al. discloses amine-containing hydrocarbons attached to a solid inorganic support such as silica or silica gel wherein the ligand is bound to the solid inorganic support through a hydrocarbon spacer containing a trialkoxysilane group. U.S. Pat. Nos. 5,071,819 and 5,084,430 to Tarbet et al. disclose sulfur and nitrogen-containing hydrocarbons as ion-binding ligands. U.S. Pat. Nos. 4,959,153 and 5,039,419 to Bradshaw et al. disclose sulfur-containing hydrocarbon ligands. U.S. Pat. Nos. 4,943,275 and 5,179,213 to Bradshaw et al. disclose ion-binding crowns and cryptands as ligands. U.S. Pat. No. 5,182,251 to Bruening et al. discloses aminoalkylphosphonic acid-containing hydrocarbons ligands. U.S. Pat. No. 4,960,882 to Bradshaw discloses proton-ionizable macrocyclic ligands. U.S. Pat. No. 5,078,978 to Tarbet et al. discloses pyridine-containing hydrocarbon ligands U.S. Pat. No. 5,244,856 to Bruening et al. discloses polytetraalkylammonium and polytrialkylamine-containing hydrocarbon ligands. U.S. Pat. No. 5,173,470 to Bruening et al. discloses thiol and/or thioether-aralkyl nitrogen-containing hydrocarbon ligands. U.S. Pat. No. 5,190,661 to Bruening et al. discloses sulfur-containing hydrocarbon ligands also containing electron withdrawing groups. Copending application Ser. No. 08/058,437 filed May 7, 1993, discloses oxygen donor macrocycles, for example, ligands containing macrocyclic polyether cryptands, calixarenes, and spherands, multiarmed ethers and mixtures of these. All of these previous reports have involved binding of the ligands to solid inorganic supports via a silane-containing spacer grouping. However, researchers have not previously reported incorporating complex, strongly interacting and highly selective ion-binding ligands into membranes which would be highly desirable because of the high surface-to-area ratios, convenient physical formats, ease of production, ease of use, and inexpensive cost of such membranes. The present invention successfully accomplishes this feat.
SUMMARY OF THE INVENTION
The compositions of the present invention comprise ion-binding ligands that are covalently bonded to a membrane through an amide, ester, thioester, carbonyl or other suitable bond. Membranes that are inherently hydrophilic, or partially hydrophilic, and contain moieties appropriate for making these bonds are preferred. Such membranes include polyamides, such as nylon, and cellulosic materials, such as cellulose, regenerated cellulose, cellulose acetate, and nitrocellulose. If the membrane used does not contain reactive groups it may be modified or derivatized appropriately. Composite membranes are also useful. A composite membrane comprises a porous polymer membrane substrate and an insoluble, cross-linked coating deposited thereon. Representative suitable polymers forming the membrane substrate include fluorinated polymers including poly(tetrafluoroethylene) (“TEFLON”), polyvinylidene fluoride (PVDF), and the like; polyolefins such as polyethylene, ultra-high molecular weight polyethylene (UPE), polypropylene, polymethylpentene, and the like; polystyrene or substituted polystyrenes; polysulfones such as polysulfone, polyethersulfone, and the like; polyesters including polyethylene terephthalate, polybutylene terephthalate, and the like; polyacrylates and polycarbonates; and vinyl polymers such as polyvinyl chloride and polyacrylonitriles. Copolymers can also be used for forming the polymer membrane substrate, such as copolymers of butadiene and styrene, fluorinated ethylene-propylene copolymer, ethylene-chlorotrifluoroethylene copolymer, and the like.
With composite membranes, the substrate membrane material is not thought to affect the performance of the derivatized membrane and is limited in composition only by its ability to be coated, or have deposited on its surface, an insoluble polymer layer that contains the appropriate reactive group. This provides a hydrophilic layer which interacts well with water or other aqueous solutions. The end result is that when an organic ligand is attached to the surface of either a hydrophilic membrane or a composite membrane having a hydrophilic surface, the basic characteristics of any given ligand molecule are not changed by the process of attaching it to the surface or by the nature of the surface itself.
The coating of composite membranes comprises a polymerized cross-linked monomer. Representative suitable polymerizable monomers include hydroxyalkyl acrylates or methacrylates including 1-hydroxyprop-2-yl acrylate and 2-hydroxyprop-1-yl acrylate, hydroxypropylmethacrylate, 2,3-dihydroxypropyl acrylate, hydroxyethylacrylate, hydroxyethyl methacrylate, and the like, and mixtures thereof. Other polymerizable monomers that can be utilized include acrylic acid, 2-N,N-dimethylaminoethyl methacrylate, sulfoethylmethacrylate and the like, acrylamides, methacrylamides, ethacrylamides, and the like. Other types of hydrophilic coatings that can be used within the scope of the invention include epoxy functional groups such as glycidyl acrylate and methacrylate, primary amines such as aminoethyl methacrylates, and benzyl derivatives such as vinyl benzyl chloride, vinyl benzyl amine, and p-hydroxyvinyl benzene.
The coating of composite membranes also comprises a precipitated crystal system, such as that involving the material known under the trademark “NAFION.” “NAFION” is a sulfonic acid or sodium sulfonate of a perfluorinated polyether.
The basic consideration in selecting a composite membrane is that the coating placed on the membrane substrate is the determining factor in defining the chemistry used to covalently attach the ligand. For example, a composite membrane displaying a carboxylic acid functional group can form an amide bond with a pendant amine group from the ligand, one of the most stable methods of ligand immobilization. The composite polymers referenced above can be prepared with carboxylic acid active groups that can be readily converted to amides upon reaction with an amine group on a ligand. However, any of the other organic species which are reactive toward an acid chloride could be used to attach an organic ligand to the surface. Additional examples of such groups would be esters, thioesters, Grignard reagents, and the like.
If the reactive group on the surface is a sulfonic acid, then an analogous procedure using a sulfonyl chloride would yield results similar to those obtained with carboxylic acid functionalities. One such polymer containing sulfonic acid reactive groups is available under the tradename “NAFION” from DuPont as described above.
The ligand is selected from the group consisting of amine-containing hydrocarbons, sulfur and nitrogen-containing hydrocarbons, sulfur-containing hydroca
Bruening Ronald L.
Di Leo Anthony J.
Goddard Philip M.
Scarmoutzos Louis M.
Tarbet Bryon J.
Fortuna Ana
Hamilton Brook Smith & Reynolds P.C.
Mykrolis Corporation
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