REMOVING METAL IONS FROM AQUEOUS SYSTEMS WITH AN ACTIVE LAYER MEMBRANE

Abstract

A process for removing metal ions from aqueous systems is disclosed comprising the treatment of the aqueous system with a membrane M, wherein the membrane M has a molecular weight cut-off above 3,000 Da and comprises A.) a carrier membrane CM, wherein said carrier membrane CM has a porous structure wherein the average pore diameter on one surface is smaller than in the rest of the membrane, thus forming rejection layers R on one side of carrier membrane CM, and B.) an active layer A comprising at least one polymer P comprising a plurality of functional groups G capable of forming stable complexes with metal ions selected from Ca, Mg, Al, Cu, Ni, Pb, Zn, Sb, Co, Cr, Cd, Hg and/or Ag, wherein said active layer A is located on the surfaces of the rejection layers R of carrier membrane CM and throughout the porous structure of carrier membrane CM.

Claims

1. A process for removing metal ions from an aqueous system, the process comprising treating the aqueous system with a membrane M, wherein the membrane M has a molecular weight cut-off above 3,000 Da and comprises A. a carrier membrane CM, wherein said carrier membrane CM has a porous structure wherein an average pore diameter on one surface is smaller than in the rest of the membrane, thus forming a rejection layer R on one side of carrier membrane CM, and B. an active layer A comprising at least one polymer P comprising a plurality of functional groups G capable of forming stable complexes with metal ions selected from Ca, Mg, Al, Cu, Ni, Pb, Zn, Sb, Co, Cr Cd, Hg and/or Ag, wherein said active layer A is located on a surface of the rejection layer R of carrier membrane CM and throughout the porous structure of carrier membrane CM.

2. The process of claim 1, wherein said carrier membrane CM is a hollow fiber membrane comprising one or more channels with an inside with an inner surface and an outside with an outer surface and wherein said rejection layer R is formed on an inside or on an outside of carrier membrane CM.

3. (canceled)

4. The process of claim 1, wherein said rejection layer R is located on an inside of carrier membrane CM.

5. The process of claim 1, wherein said rejection layer R is located on an outside of carrier membrane CM.

6. The process of claim 1, wherein said active layer A is obtained from at least one polymer P that has optionally been crosslinked with at least one crosslinker V, wherein said at least one polymer P is selected from linear or branched polyethyleneimine PEI, polyalkylenepolyamine, thiol-based polyethylenimine PEI, melamine based polymers, polyetheramine, polyvinylamine, polyamidoamine, quarternary amine based polymers polyacrylic acid or salts thereof, polydiallyl-dimethyl-ammonium chloride, humic substances, carboxyl methyl cellulose, and copolymers of acrylic acid and other ethylenically unsaturated compounds.

7. The process of claim 6, wherein said at least one polymer P is at least one polyethyleneimine PEI that was crosslinked with at least one crosslinker V.

8. The process of claim 6, wherein said crosslinker V comprises functional groups F which are acyl groups.

9. The process of claim 6, wherein said crosslinker V is selected from trimesoylchloride, phthaloyl chloride (1,2-benzenedicarbonyl chloride), isophthaloyl chloride (1,3-benzenedicarbonyl chloride), terephthaloyl chloride (TCL, 1,4-benzenedicarbonyl chloride), mm-Biphenyl tetraacyl chloride (mm-BTEC), om-Biphenyl tetraacyl chloride (om-BTEC), op-Biphenyl tetraacyl chloride (op-BTEC) and 5-chloroformyloxy-isophthaloyl chloride (CFIC), cyanuric chloride, glutaryl chloride, hexafluoroglutaryl chloride, glutaraldehyde, formaldehyde, acetalde-hyde, propionaldehyde, butyraldehyde, benzaldehyde, glucose, imidazolate-2-carboxyaldehyde, iso-phthalaldehyde, ortho-phthaldialdehyde and tere-phthalaldehyde.

10. The process of claim 6, wherein said polyethyleneimine PEI has an average molar mass MW of 500 to 1,000,000 Da.

11. The process of claim 1, wherein said carrier membrane CM is selected from ultrafiltration membranes and microfiltration membranes.

12. The process of claim 1, wherein said carrier membrane CM comprises as its main component at least one polymer selected from polysulfone, polyphenylenesulfone, polyethersulfone, and mixtures thereof.

13. The process of claim 1, wherein the aqueous system comprises industrial waste water, municipal waste water, sea water, brackish water, fluvial water, surface water, drinking water, mining water, waste water from an oil well and/or waste water from a power plant.

14. A membrane M as defined in claim 1.

15. A process for making a membrane M as defined in claim 1, the process comprising: a) Providing a carrier membrane CM wherein said carrier membrane CM is a hollow fiber membrane having one or more channels with an inside with an inner surface and an outside with an outer surface, wherein said carrier membrane CM has a porous structure wherein an average pore diameter on one surface is smaller than in the rest of the membrane, thus forming a rejection layer R on an inside or on an outside of carrier membrane CM, b) Optionally applying a solution S1 comprising at least one crosslinker V and at least one solvent SV to the surface of carrier membrane CM where the rejection layer R is located, c) Removing said at least one solvent SV at least partially from carrier membrane CM such that crosslinker V remains at least partially on a surface and/or in the pore structure of carrier membrane CM, d) Applying a solution S2 comprising at least one polymer P and at least one solvent SP to the surface of carrier membrane CM where the rejection layer R is located, e) Removing said at least one solvent SP from carrier membrane CM, f) Optionally curing active layer A at a temperature from 40 to 100 C.

16. The process of claim 15, wherein said at least one solvent SV is a hydrocarbon.

17. The process of claim 15, wherein solvent SP is selected from water and alcohols.

Description

EXAMPLES

[0121] Inge Multibore Membrane 0.9: multichannel hollow fiber membrane made of polyethersulfone comprising seven channels with an inner diameter of each channel of 0.9 mm and an overall diameter of the multibore membrane of 4.0 mm and an average pore diameter in the rejection layer of 20 nm with the rejection layer being located on the lumen side. [0122] Inge Multibore Membrane 1.5: multichannel hollow fiber membrane made of polyethersulfone comprising seven channels with an inner diameter of each channel of 1.5 mm and an overall diameter of the multibore membrane of 6.0 mm and an average pore diameter in the rejection layer of 20 nm with the rejection layer being located on the lumen side.

Example 1-12: Inside-Out Coating of UF Membranes

[0123] The crosslinker trimesoylchloride (TMC) (0.025 wt %) in n-hexane solution was pumped from the lumen side of hollow fibers into the porous structure of a Inge Multibore Membrane 0.9 for 3 min with the end of the module capped (see FIG. 1) to force the solution out into the porous structure. A purged sweeping air was applied for 2 min to remove the residual solvents/droplets in the same fashion. Hyper-branched polyethyleneimine (PEI) (2-4 wt %, molecular weight of 800-25,000 Da, see Table 1) aqueous solution in deionized water with molecular weights and weight percentage as given in Table 1 were then brought into contact with the TMC saturated surface on the membrane porous structure for 3 min with the module end capped to force the solution out into the porous structure. The excess PEI residual solutions or droplets were removed by purging a sweeping air for 6 min using a compressed air gun. The resultant coated membranes were then heat-cured at 65 C. for 15 min. The membranes were subsequently stored in deionized water overnight before UF and ion rejection testing.

Example 13-16: Modified Inside-Out Coating of Active UF Membranes

[0124] Prior to coating, isopropanol was pumped through the membrane for 1 min, followed by n-hexane for 1 min. The crosslinker trimesoylchloride (0.025 wt %) in n-hexane solution was pumped from the lumen side of hollow fibers into the porous structure of the Inge Multibore Membrane 0.9 for 3 min with the end of the module capped (see FIG. 1) to force the solution out into the porous structure. A purged sweeping air was applied for 2 min to remove the residual solvents/droplets in the same fashion. Hyper-branched polyethyleneimine (PEI) (2-4 wt %, molecular weight of 800-25,000 Da, see Table 1) aqueous solution in deionized water with molecular weights and weight percentage as given in Table 1 were then brought into contact with the TMC saturated surface on the membrane porous structure for 3 min with the module end capped to force the solution out into the porous structure. The excess PEI residual solutions or droplets were removed by purging a sweeping air for 6 min using a compressed air gun. The resultant coated membranes were then heat-cured at 65 C. for 15 min. The membranes were subsequently stored in deionized water overnight before UF and ion rejection testing.

Example 17-18: Glutaraldehyde-Crosslinked Coating of PEI

[0125] Inge Multibore Membrane 1.5 were used in these examples. Polyethyleneimine (6 wt %, molecular weight of 800) aqueous solution in deionized water at 65 C. was pumped through the membrane porous structure for 5 min. Then, a purged sweeping air was applied for 6 min to push the residual solvents/droplets out from the lumen into the porous structure. Glutaraldehyde (a crosslinker) solution (0.5 wt %) in deionized water at 65 C. was then pumped through the membrane for 3 min. The membrane was then heat-cured at 65 C. for 15 min. After which, it was immersed in deionized water overnight until further UF and rejection tests using synthetic brackish water.

Testing of Membranes Prepared According to Examples 1 to 18

[0126] For performance test of coated membranes, deionized water was pumped through the fiber for 30 min with a trans-membrane pressure (TMP) of 0.4 bar and the pure water permeability (PWP) was taken. The water flux (Lm.sup.2 h.sup.1 bar.sup.1, abbreviated as LMH/bar) is calculated as follows:

Jv=V/(AtP), where V is the volume collected at a determined time (t) at a pressure of P and membrane surface area of A.

[0127] Polyethyleneglycol (PEG) solution (1000 ppm) with molecular weight 2,000, 3,000, 4,000, 6,000, 8,000, 10,000, 12,000, 20,000 and 100,000 was then pumped through the fiber for 15 min with TMP of 0.15 bar and the feed, permeate were collected for molecular weight cut-off (MWCO) determination. The relationship between Stokes radius (r.sub.s, nm) and molecular weight (Mw, gmol.sup.1) of these neutral solutes can be expressed as:

For PEG: r=16.7310.sup.12M.sup.0.557(2)

[0128] The comparison of the coated membranes' performance against that of inge Multibore 0.9 membrane's is given in table 2.

[0129] For ion rejection test of coated membranes for example 1-16, a solution containing metal/contaminant ion [Cu(NO.sub.3).sub.2] (concentration of 2.5-20 ppm, pH range of 5-7) was pumped through the fiber for 1-14 h. Both feed and permeate solutions were analyzed for the reduction in copper (II) concentration over time using Inductively Coupled PlasmaOptical Emission Spectroscopy (ICP-OES) to calculate the metal ion rejection, r=100(c.sub.feedc.sub.permeate)/c.sub.feed.

[0130] The short term results (up to 2 h) are given in tables 4-8, 12-15 while the long term results are given in table 9.

[0131] For synthetic brackish water rejection test for example 17-18, a solution containing Cu.sup.2+ (concentration of 0.4-0.5 ppm), Na.sup.+ (concentration of 547-551 ppm), Mg.sup.2+ (concentration of 52-58 ppm) and Ca.sup.2+ (concentration of 13-14 ppm) with pH adjusted to 7.0 was pumped through the fiber for 2-7 h. Both feed and permeate solutions were analyzed for the reduction in copper (II) concentration over time using Inductively Coupled PlasmaOptical Emission Spectroscopy (ICP-OES) to calculate the metal ion rejection, r=100(c.sub.feedc.sub.permeate)/c.sub.feed.

[0132] The short term results (up to 2 h) are given in tables 16 while the long term results are given in table 17.

[0133] The ion solution permeability was also collected. Deionized water with pH adjustment to 2, followed by pure deionized water was then pumped through the fiber for a total of 15-30 min to regenerate the membrane. The second PWP was taken and the flux recovery was calculated from the ratio between the first and second PWP.

[0134] For regeneration studies, deionized water with pH adjustment to 2 was pumped through the fiber followed by a solution containing metal/contaminant ion [Cu(NO.sub.3).sub.2] (concentration of 2.5-20 ppm, pH range of 5-7) to investigate the change in rejection after regeneration. The regeneration of coated multibore in example 11 and 12 are given in table 10-11.

TABLE-US-00001 TABLE 1 Performance and ion rejection of membranes coated according to examples 1 to 16 PEI Performance test Molecular Pure water Ion solution Ion rejection test weight/ permeability/ MWCO/ permeability/ Metal ion Flux Ex. Da Weight/% LMH bar.sup.1 Da LMH bar.sup.1 rejection/% recovery/% 1 25 000 0.5 227.45 42.44 104.03 2 25 000 0.5 316.52 32.81 96.63 3 25 000 0.5 330.21 11 ,476 4 25 000 0.5 193.79 10, 787 5 800 2.0 563.69 72.47 1.48 99.63 6 800 2.0 643.69 82.06 3.42 114.71 7 800 2.0 781.90 31, 815 8 800 2.0 686.47 63, 195 9 800 2.0 711.43 701.65 75.30 1.19 10 800 2.0 655.2 368.35 76.13 2.38 77.09* 11 800 2.0 748.59 16.30 0.41 12 800 2.0 765.7 691.87 15.28 0.45 13 800 2.0 415.61 451.06 69.06 2.48 14 800 2.0 325.97 375.52 66.86 3.09 15 800 2.0 340.64 368.02 Cu: 64.64 3.4.sup. Zn: 61.99 0.7.sup. 16 800 2.0 432.24 467.69 Cu: 67.88 5.4.sup. Zn: 64.08 0.7.sup. *After long-term ion rejection test of 14 h

TABLE-US-00002 TABLE 2 Comparison between inge multibore 0.9 membrane and inside-out method PWP MWCO Code (LMH/bar) (Da) inge multibore 0.9 1405 171, 774 6, 950 Example 7 a* 681 79 47, 505 15, 690 *With same coating procedure as Ex 7, but 0.5 wt % HPEI (Mw of 25 KDa), 0.025 wt % TMC

TABLE-US-00003 TABLE 3 PEI Performance test Molecular GA Pure water Ion solution weight/ Weight Weight permeability/ permeability/ Ex. Da percentage/% percentage LMH bar.sup.1 LMH bar.sup.1 17 800 6.0 0.5 125.17 118.72 18 800 6.0 0.5 247.80 236.90

TABLE-US-00004 TABLE 4 Short-term ion rejection test for Example 1 Cu.sup.2+ Feed Cu.sup.2+ Permeate concentration/ concentration/ Time/min ppm ppm Rejection/% 0 23.8 0.58 97.56 2 23.8 8.60 63.87 4 23.8 12.50 47.48 6 23.8 13.70 42.44 8 23.8 13.70 42.44

TABLE-US-00005 TABLE 5 Short-term ion rejection test for Example 2 Cu.sup.2+ Feed Cu.sup.2+ Permeate concentration/ concentration/ Time/min ppm ppm Rejection/% 0 19.2 0.03 99.84 2 19.2 3.9 79.69 4 19.2 10.7 44.27 6 19.2 12.9 32.81

TABLE-US-00006 TABLE 6 Short-term ion rejection test for Example 5 Cu.sup.2+ Feed Cu.sup.2+ Permeate concentration/ concentration/ Time/min ppm ppm Rejection/% 0 2.5 0.24 90.40 5 2.5 0.55 78.00 10 2.5 0.63 74.80 15 2.5 0.64 74.40 20 2.5 0.68 72.80 25 2.5 0.69 72.40 30 2.5 0.69 72.40 35 2.5 0.68 72.80 40 2.5 0.72 71.20 45 2.5 0.75 70.00 50 2.5 0.74 70.40 55 2.5 0.68 72.80 60 2.5 0.67 73.20

TABLE-US-00007 TABLE 7 Short-term ion rejection test for Example 6 Cu.sup.2+ Feed Cu.sup.2+ Permeate concentration/ concentration/ Time/min ppm ppm Rejection/% 0 2.7 0 100.00 2 2.7 0.29 89.26 4 2.7 0.39 85.56 6 2.7 0.38 85.93 8 2.7 0.29 89.26 10 2.7 0.68 74.81 15 2.7 0.45 83.33 20 2.7 0.48 82.22 25 2.7 0.53 80.37 30 2.7 0.49 81.85 35 2.7 0.49 81.85 40 2.7 0.49 81.85 45 2.7 0.50 81.48 50 2.7 0.49 81.85 55 2.7 0.55 79.63 60 2.7 0.57 78.89

TABLE-US-00008 TABLE 8 Short-term ion rejection test for Example 9 Cu.sup.2+ Feed Cu.sup.2+ Permeate concentration/ concentration/ Time/min ppm ppm Rejection/% 0 2.5 0.01 99.60 2 2.5 0.44 82.40 4 2.5 0.74 70.40 6 2.5 0.64 74.40 8 2.5 0.62 75.20 10 2.5 0.60 76.00 20 2.5 0.68 72.80 30 2.5 0.61 75.60 40 2.5 0.59 76.40 50 2.5 0.60 76.00 60 2.5 0.60 76.00

TABLE-US-00009 TABLE 9 Long-term ion rejection test for Example 10 Cu.sup.2+ Feed Cu.sup.2+ Permeate concentration/ concentration/ Time/min ppm ppm Rejection/% 0 2.7 0.00 99.93 2 2.7 0.00 99.93 4 2.7 0.42 84.53 8 2.7 0.52 80.74 10 2.7 0.57 79.00 15 2.7 0.57 78.89 20 2.7 0.65 75.92 25 2.7 0.57 78.96 30 2.7 0.60 77.92 45 2.7 0.61 77.29 60 2.7 0.67 75.25 75 2.7 0.67 75.03 90 2.7 0.69 74.47 230 2.7 0.64 76.36 245 2.7 0.79 70.80 300 2.7 0.71 73.62 360 2.7 0.63 76.62 390 2.7 0.517 80.56 420 2.7 0.498 81.30 450 2.7 0.507 80.96 480 2.7 0.529 80.14 510 2.7 0.513 80.74 570 2.7 0.559 79.01 630 2.7 0.51 80.85 690 2.7 0.565 78.78 780 2.7 0.445 83.29 840 2.7 0.514 80.70

TABLE-US-00010 TABLE 10 Regeneration studies for Example 11 Cu.sup.2+ Feed Cu.sup.2+ Permeate concentration/ concentration/ Time/min ppm ppm Rejection/% 0 18.18 9.68 46.76 2 18.18 15.79 13.16 4 18.18 16.18 10.99 6 18.18 16.19 10.96 8 18.18 15.58 14.32 10 18.18 16.25 10.63 15 18.18 16.48 9.37 20 18.18 16.24 10.69 40 18.18 16.97 6.64 41 18.18 9.69 46.73 42 18.18 14.71 19.08 44 18.18 14.34 21.14 46 18.18 14.73 18.97 48 18.18 14.59 19.76 50 18.18 14.82 18.50 60 18.18 14.30 21.33 80 18.18 14.90 18.06

TABLE-US-00011 TABLE 11 Regeneration studies for Example 12 Cu.sup.2+ Feed Cu.sup.2+ Permeate Time/ concentration/ concentration/ min ppm ppm Rejection/% 0 17.97 9.58 46.71 2 17.97 14.86 17.30 4 17.97 15.28 15.00 6 17.97 15.29 14.94 8 17.97 15.61 13.13 10 17.97 15.17 15.58 15 17.97 15.81 12.02 20 17.97 14.50 19.31 40 17.97 16.43 8.60 41 17.97 10.52 41.45 42 17.97 15.76 12.30 44 17.97 15.52 13.63 46 17.97 14.25 20.73 48 17.97 14.57 18.95 50 17.97 15.20 15.41 60 17.97 14.52 19.22 80 17.97 14.40 19.86

TABLE-US-00012 TABLE 12 Short-term ion rejection test for Example 13 Cu.sup.2+ Feed Cu.sup.2+ Permeate Time/ concentration/ concentration/ min ppm ppm Rejection/% 0 1.947 0.003 99.84 2 1.947 0.042 97.84 4 1.947 0.205 89.47 6 1.947 0.378 80.60 8 1.947 0.478 75.46 10 1.947 0.527 72.94 15 1.947 0.590 69.69 20 1.947 0.610 68.66 50 1.947 0.650 66.59 60 1.947 0.635 67.39

TABLE-US-00013 TABLE 13 Short-term ion rejection test for Example 14 Cu.sup.2+ Feed Cu.sup.2+ Permeate Time/ concentration/ concentration/ min ppm ppm Rejection/% 0 1.909 0.001 99.97 2 1.909 0.086 95.49 4 1.909 0.244 87.23 6 1.909 0.397 79.21 8 1.909 0.490 74.30 10 1.909 0.548 71.27 15 1.909 0.618 67.61 20 1.909 0.618 67.61 50 1.909 0.684 64.16 60 1.909 0.694 63.66

TABLE-US-00014 TABLE 14 Short-term copper (II), zinc (II) rejection for Example 15 Cu.sup.2+ Cu.sup.2+ Zn.sup.2+ Zn.sup.2+ Feed Permeate Feed Permeate Cu.sup.2+ Zn.sup.2+ concen- concen- concen- concen- Re- Re- Time/ tration/ tration/ tration/ tration/ jection/ jection/ min ppm ppm ppm ppm % % 0 0.919 0.001 1.098 0.000 99.92 100.00 2 0.919 0.005 1.098 0.561 99.45 48.92 4 0.919 0.012 1.098 0.469 98.69 57.23 6 0.919 0.054 1.098 0.430 94.16 60.78 8 0.919 0.115 1.098 0.421 87.49 61.60 10 0.919 0.187 1.098 0.415 79.66 62.19 15 0.919 0.282 1.098 0.408 69.33 62.80 20 0.919 0.324 1.098 0.423 64.80 61.50 50 0.919 0.339 1.098 0.408 63.16 62.80 60 0.919 0.356 1.098 0.414 61.25 62.28

TABLE-US-00015 TABLE 15 Short-term copper (II), zinc (II) rejection for Example 16 Cu.sup.2+ Cu.sup.2+ Zn.sup.2+ Zn.sup.2+ Feed Permeate Feed Permeate Cu.sup.2+ Zn.sup.2+ concen- concen- concen- concen- Re- Re- Time/ tration/ tration/ tration/ tration/ jection/ jection/ min ppm ppm ppm ppm % % 0 0.915 0.000 1.054 0.000 100.00 100.00 2 0.915 0.004 1.054 0.516 99.57 51.05 4 0.915 0.011 1.054 0.449 98.83 57.39 6 0.915 0.046 1.054 0.410 94.93 61.11 8 0.915 0.102 1.054 0.390 88.83 63.00 10 0.915 0.152 1.054 0.377 83.37 64.21 15 0.915 0.232 1.054 0.372 74.63 64.67 20 0.915 0.278 1.054 0.373 69.67 64.63 50 0.915 0.323 1.054 0.374 64.67 64.49 60 0.915 0.343 1.054 0.385 62.56 63.49

TABLE-US-00016 TABLE 16 Short-term copper (II) rejection for Example 17 Cu.sup.2+ feed Cu.sup.2+ permeate concentration/ concentration/ Time/min ppm ppm Rejection/% 0 0.557 0.000 100.00 2 0.557 0.000 100.00 4 0.557 0.000 100.00 6 0.557 0.000 100.00 8 0.557 0.000 100.00 10 0.557 0.000 100.00 15 0.557 0.000 100.00 20 0.557 0.005 99.11 40 0.557 0.055 90.14 60 0.557 0.110 80.28 80 0.557 0.176 68.47 100 0.557 0.220 60.51 120 0.501 0.297 40.76 140 0.501 0.333 33.52 160 0.501 0.365 27.13 180 0.501 0.382 23.73 200 0.501 0.391 22.03 220 0.501 0.404 19.47

TABLE-US-00017 TABLE 17 Long-term copper (II) rejection for Example 18 Cu.sup.2+ feed Cu.sup.2+ permeate concentration/ concentration/ Time/min ppm ppm Rejection/% 0 0.361 0.000 100.00 2 0.361 0.000 100.00 4 0.361 0.000 100.00 6 0.361 0.000 100.00 8 0.361 0.000 100.00 10 0.361 0.000 100.00 15 0.361 0.000 100.00 20 0.361 0.000 100.00 40 0.361 0.000 100.00 60 0.361 0.000 100.00 80 0.361 0.001 99.76 100 0.361 0.044 87.78 120 0.361 0.090 75.06 140 0.361 0.129 64.24 160 0.361 0.140 61.27 180 0.361 0.149 58.83 220 0.375 0.150 60.12 240 0.375 0.199 47.05 260 0.375 0.216 42.29 280 0.375 0.226 39.77 300 0.375 0.238 36.57 320 0.330 0.198 39.85 340 0.330 0.235 28.75 360 0.330 0.250 24.23 380 0.330 0.258 21.88 400 0.330 0.249 24.56 420 0.330 0.252 23.66