Additives for boron rejection enhancement of a membrane

1. A process for preparing a thin film composite membrane, comprising:

(a) preparing an aqueous phase comprising a polyamine and an organic phase comprising a polyfunctional acid halide, wherein the aqueous phase or organic phase or both include an additive comprising:

a boron rejection-enhancing additive having the formula:

wherein:

the formula represents a recurring polymer unit;

n is a number between 1 and 60; and

X is an alkyl chain having between 1 and 30 carbons; and

(b) applying the aqueous phase to a surface of a porous support membrane to form a coated support membrane; and

(c) applying the organic phase to the coated support membrane and interfacially polymerizing the polyamine and the polyfunctional acid halide to form a discrimination layer of a thin film composite membrane comprising the porous support membrane and the discrimination layer, the thin film composite membrane having a boron rejection that is greater than the boron rejection of a thin film composite membrane prepared in the absence of the boron rejection-enhancing additive.

2. The process of claim 1 , wherein X is —(CH 2 ) 6 —.

3. The process of claim 1 , wherein the concentration of boron rejection-enhancing additive in the aqueous phase or organic phase is from about 0.01% to 5% based on the weight of the aqueous phase or organic phase.

4. The process of claim 1 , wherein the aqueous phase or organic phase or both further include a metal chelate additive containing a bidentate ligand and a metal atom or metal ion.

5. The process of claim 4 , wherein the bidentate ligand is selected from among:

wherein each of R 1 , R 2 , R 3 , R 4 and R 5 separately is selected from among a C 1 -C 10 alkyl, a halogenated C 1 -C 10 alkyl, a 5-membered aromatic ring, a 6-membered aromatic ring, an aromatic bicyclic ring, system containing two fused 6-membered rings, and an aromatic bicyclic ring system containing a 5-membered ring fused to a 6-membered aromatic ring.

6. The process of claim 4 , wherein the bidentate ligand is an acetylacetonate (acac) or fluorinated acetylacetonate.

7. The process of claim 4 , wherein the metal chelate additive containing a bidentate ligand and a metal atom or metal ion is selected from among Al(acac) 3 , Al(F 6 acac) 3 , Ba(acac) 2 , Ba(F 6 acac) 2 , Be(acac) 2 , Be(F 6 acac) 2 , Ca(acac) 2 , Ca(F 6 acac) 2 , Cd(acac) 2 , Cd(F 6 acac) 2 , Ce(acac) 3 , Ce(F 6 acac) 3 , Cr(acac) 3 , Co(acac) 2 , Cu(acac) 2 , Cu(F 6 acac) 2 , Dy(acac) 3 , Er(acac) 3 , Fe(acac) 2 , Fe(acac) 3 , Ga(acac) 3 , Hf(acac) 4 , In(acac) 3 , K(acac), Li(acac), Mg(acac) 2 , Mg(F 6 acac) 2 , Mn(acac) 2 , Mn(acac) 3 , MoO(acac) 2 , MoO(F 6 acac) 2 , Na(acac), Nd(acac) 3 , Nd(F 6 acac) 3 , Ni(acac) 2 , Ni(F 6 acac) 2 , Pd(acac) 2 , Pr(acac) 3 , Pr(F 6 acac) 3 , Ru(acac) 3 , Ru(F 6 acac) 3 , Sc(acac) 2 , Sc(F 6 acac) 2 , Sm(acac) 3 , Sn(acac) 2 , Sn(acac) 2 Cl 2 , t-butyl-Sn(acac) 2 , t-butyl-Sn(acac) 2 Cl 2 , Sn(F 6 acac) 2 , Sr(acac) 2 , Sr(F 6 acac) 2 , Tb(acac) 3 , V(acac) 3 , Y(acac) 3 , Y(F 6 acac) 3 , Zn(acac) 2 , Zn(F 6 acac) 2 , and Zr(acac) 4 , wherein F 6 acac refers to 1,1,1,5,5,5-hexafluoroacetylacetonate.

8. The process of claim 4 , wherein the bidentate ligand is a beta-diketonate or a fluorinated beta-diketonate.

9. The process of claim 4 , wherein the amount of bidentate ligand in the metal chelate additive yields a concentration of bidentate ligand in the aqueous phase of step (a) of from about 0.001 wt % to about 1 wt %, based on the weight of the aqueous phase.

10. The process of claim 4 , wherein the metal atom or metal ion is an alkaline earth metal.

11. A thin film composite membrane prepared according to the process of claim 1 .