Extraction Of Anions From Solutions And Mixtures Using Hyperbranched Macromolecules

Abstract

Hyperbranched macromolecules and methods are described for selectively filtering contaminants such as anions from water and non-aqueous solutions, particularly in the presence of competing contaminants including other anions. The hyperbranched macromolecules may contain 2-hydroxyalkyl, 2-methyl-2-hydroxylalkyl, and other groups, which may be hydrophilic or hydrophobic. The molecules may preferentially bind to the contaminant at interest at low pH, and release the contaminant at a pH of about 9. The molecules may be used to filter contaminants including perchlorate and nitrate even in the presence of high sulfate concentrations.

What is claimed is: 
     
         1 . A hyperbranched macromolecule (A) comprising a plurality of branches and a plurality of terminal functional groups within the same molecular structure;
 wherein each branch comprises an N-substituted or N,N-substituted n-aminoalkyl moiety (B);   wherein each substituent to moiety B comprises either:
 (a) another of said plurality of branches; or 
 (b) one of the plurality of terminal functional groups; 
   wherein A has a hyperbranched structure with a molecular weight of at least 1500 grams per mole;   wherein A comprises essentially no primary amine moieties; and   wherein each of the plurality of terminal functional groups is selected from the group consisting of 2-hydroxyalkyl and 2-methyl-2-hydroxyalkyl.   
     
     
         2 . The macromolecule of  claim 1 , wherein each of the terminal functional groups is a 2-hydroxyalkyl group. 
     
     
         3 . The macromolecule of  claim 1 , wherein each of the terminal functional groups is a 2-methyl-2-hydroxyalkyl group. 
     
     
         4 . The macromolecule of  claim 1 , wherein the degree of branching of A is in the range of about 65% to about 70%. 
     
     
         5 . The macromolecule of  claim 1 , wherein A comprises essentially no secondary amine moieties. 
     
     
         6 . The macromolecule of  claim 1 , wherein each of the plurality of terminal functional groups is a hydrophobic group. 
     
     
         7 . The macromolecule of  claim 1 , wherein A is water soluble at standard temperature and pressure. 
     
     
         8 . The macromolecule of  claim 1 , wherein A is water insoluble at standard temperature and pressure. 
     
     
         9 . The macromolecule of  claim 1 , wherein the acidic binding capacity X is at least twice the basic binding capacity Y with respect to an anion,
 wherein X is the binding capacity that is measured after placing A and an excess amount of the anion in water at pH 7.0 at room temperature, and adding a sufficient amount of acid to achieve a pH of 5.0; and   wherein Y is the binding capacity that is measured after placing A and an excess amount of the anion in water at pH 7.0 at room temperature, and adding a sufficient amount of base to achieve a pH of 9.0.   
     
     
         10 . The macromolecule of  claim 9 , wherein X is at least 5 times greater than Y. 
     
     
         11 . The macromolecule of  claim 10 , wherein X is at least 10 times greater than Y. 
     
     
         12 . The macromolecule of  claim 9 , wherein the anion is selected from the group consisting of perchlorate and nitrate. 
     
     
         13 . The macromolecule of  claim 9 , wherein the water is deionized water. 
     
     
         14 . The macromolecule of  claim 9 , wherein the water contains 175 parts per million of sulfate ions. 
     
     
         15 . A filtration method comprising:
 providing a solution containing a first quantity of a contaminant;   contacting the solution with a first quantity of a hyperbranched macromolecule under conditions such that the first quantity of the contaminant is bound to the first quantity of the hyperbranched macromolecule to produce: (a) a composition comprising a contaminant-bound hyperbranched macromolecule, and (b) a composition comprising a relatively contaminant-depleted solution; and   separating the quantity of contaminant-bound hyperbranched macromolecules from the quantity of relatively contaminant-depleted solution;   wherein the hyperbranched macromolecule is the hyperbranched molecule of  claim 1 .   
     
     
         16 . The method of  claim 15 , wherein the solution is an aqueous solution, the hyperbranched macromolecule is water soluble, and the contaminant is an anion. 
     
     
         17 . The method of  claim 15 , wherein the hyperbranched macromolecule is water insoluble. 
     
     
         18 . The method of  claim 15 , wherein the solution is an aqueous solution, and the contaminant is an organic compound. 
     
     
         19 . The method of  claim 15 , wherein the solution is a non-aqueous solution, and the contaminant is an anion. 
     
     
         20 . The method of  claim 15 , further comprising the step of introducing the quantity of contaminant-bound hyperbranched macromolecules into an aqueous environment where the pH is greater than the pH of the aqueous environment, and wherein conditions are such that a portion of molecules of the contaminant dissociate from a portion of the hyperbranched macromolecules. 
     
     
         21 . The method of  claim 20 , further comprising the step of providing a cross-flow filter wherein the mixture of said portion of molecules of the contaminant and said portion of the hyperbranched macromolecules pass transversely across the cross-flow filter while a portion of the contaminant passes through the filter.