Reverse osmosis membrane and method of producing the same
A composite polyamide reverse osmosis membrane comprising a polyamide layer; where the polyamide layer has a thickness in the range of 50-250 nm, and large open spaces (i.e., free volumes); where the open spaces are defined by a ratio of water flux, J w , (gfd) divided by the average surface roughness, Ra, (nm) of the polyamide layer; wherein the composite polyamide reverse osmosis membrane has the ratio of J w /Ra>0.35 gfd/nm when tested at 65 psi, using an aqueous solution containing 250 ppm of NaCl; and a microporous support with a thickness ranging from 100-150 μm. The present invention also relates to processes of fabricating the composite polyamide reverse osmosis membrane.
1. A process for fabricating a composite polyamide reverse osmosis membrane, comprising:
providing a microporous support;
coating the microporous support with an aqueous solution to form a liquid layer on the microporous support, wherein the aqueous solution comprises:
a monomeric polyamine having at least two functional amine groups; wherein the monomeric polyamine is in an amount in the range of 0.1 to 20 wt % of the aqueous solution;
a single tertiary amine, wherein the single tertiary amine is in an amount in the range of 1 to 10 wt % of the aqueous solution; and
an aliphatic sulfonic acids, wherein the aliphatic sulfonic acid is in an amount in the range of 0.25 to 10.0 wt % of the aqueous solution;
wherein the aqueous solution has a pH value in the range of 5.5 to 11;
contacting the liquid layer with an organic solution to form an organic layer on top of the liquid layer; wherein the organic solution comprises:
an amine-reactive reactant and an organic solvents, wherein the amine-reactive reactant is in the range of 0.01 to 5.0 wt/vol % of the organic solution; and
drying the microporous support together with the liquid layer and organic layer at a temperature of about 50° to 180° C.;
thereby a composite polyamide reverse osmosis membrane is fabricated.
2. The process of claim 1 , wherein the monomeric polyamine is an aromatic primary diamine represented by formula (I):
wherein R 1 and R 2 are selected from the group consisting of an alkyl group, an alkoxy group, a hydroxy alkyl group, a hydroxy group, and a halogen atom, wherein R 1 and R 2 is in the meta-, ortho-, or para-position on the aromatic ring.
3. The process of claim 2 , wherein the monomeric polyamine is selected from the groups consisting of m-phenylenediamine, p-phenylenediamine, and substituted derivatives thereof.
4. The process of the claim 1 , wherein the monomeric polyamine is an aliphatic primary diamine represented by formula (II):
H 2 N—R 3 —NH 2 (II)
wherein R 3 is selected from the group consisting of a straight or a branched aliphatic hydrocarbon chain, a cycloaliphatic hydrocarbon consisting of 4 or more carbon atoms, and a branched aliphatic hydrocarbon chain containing an aromatic or cycloaliphatic ring.
5. The process of claim 1 , wherein the monomeric polyamine is an aromatic secondary diamine represented by formula (III):
wherein R 4 and R 5 are straight or branched aliphatic hydrocarbon groups, which contain aromatic rings, and wherein the R 4 and R 5 are in the meta-, ortho- or para-positions on the aromatic ring.
6. The process of claim 5 , wherein the aromatic secondary diamine is selected from the group consisting of N,N′-dimethyl-1,3-phenylenediamine, and N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine.
7. The process of claim 1 , wherein the monomeric polyamine is a cycloaliphatic, secondary diamine represented by formula (IV):
wherein R 6 is a cycloaliphatic hydrocarbon.
8. The process of claim 7 , wherein the cycloaliphatic, secondary diamine is piperazine.
9. The process of claim 1 , wherein the aliphatic sulfonic acid is represented by the formula (V)
wherein R 7 is a straight or a branched aliphatic hydrocarbon(s) and the hydrocarbon number is from C1 to C10 atoms.
10. The process of claim 9 , wherein the aliphatic sulfonic acid is selected from the group consisting of methane sulfonic acid, ethane sulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid, 3-methylbutane-1-sulfonic acid, 1-hexanesulfonic acid, 2-methylhexane-3-sulfonic acid, and 3-ethylhexane-1-sulfonic acid.
11. The process of claim 1 , wherein the single tertiary amine is represented by the formula (VI):
wherein R 8 , R 9 or R 10 is a straight or a branched aliphatic hydrocarbon and the hydrocarbon number is from C1 to C7 atoms.
12. The process of claim 11 , wherein the single tertiary amine is selected from the group consisting of trimethylamine, triethylamine, tripropylamine, and tributylamine.
13. The process of claim 1 , wherein the aqueous solution further comprises a surfactant selected from the group consisting of sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), sodium lauryl sulfate (SLS), and mixtures thereof; wherein the surfactant is the range of 0.01 to 0.5 wt % of the aqueous solution.
14. The process of claim 1 , wherein the aqueous solution further comprises an alcohol selected from the group consisting of methanol, ethanol, isopropyl alcohol, tert-butyl alcohol, and mixtures thereof; wherein the alcohol is in the range of 0.1 to 15 wt % of the aqueous solution.
15. The process of claim 1 , wherein the amine-reactive reactant is selected from the group consisting of a polyfunctional acyl halide, a polyfunctional sulfonyl halide and a polyfunctional isocyanate.
16. The process of claim 15 , wherein the amine-reactive reactant is selected from the group consisting of trimesoyl chloride (TMC), isophthaloyl chloride (IPC), terephthaloyl chloride (TPC), and mixtures thereof.
17. The process of claim 1 , wherein the organic solution further comprises an alcohol selected from the group consisting of methanol, ethanol, isopropyl alcohol, tert-butyl alcohol, and mixtures thereof; wherein the alcohol is in the range of 0.001 to 1 wt % of the organic solution.