Extraction Of Anions From Solutions And Mixtures Using Hyperbranched Macromolecules
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.
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.