A Method For Producing Ultrapure Water

Abstract

The present invention relates to a method for producing purified water comprising a step of passing water through an ultrafiltration means and a mixed bed ion exchanger comprising comprising beads having a pore size of 20-100 nm, wherein the ultrafiltration means is located upstream of said mixed bed ion exchanger, as well as to a module comprising an ultrafiltration means and a mixed bed ion exchanger and a water treatment system for producing ultrapure water comprising ultrafiltration means and a mixed bed ion exchanger.

Claims

1. A method for producing purified water comprising a step of passing water through an ultrafilter and a mixed bed ion exchanger comprising beads having a pore size of 20-100 nm, wherein the ultrafilter is located upstream of said mixed bed ion exchanger.

2. A method according to claim 1, wherein the purified water is ultrapure water.

3. A method according to claim 1, wherein the mixed bed ion exchanger consists of a mixture of anion exchange particles and cation exchange particles.

4. A method according to claim 1, wherein the mixed bed ion exchanger is based on styrene divinylbenzene.

5. A method according to claim 1, wherein the ultrafilter comprises a dead-end hydrophilic ultrafiltration membrane.

6. A method according claim 1, wherein the ultrafilter comprises an air evacuator.

7. A method according to claim 1, wherein the method comprises a further step of passing water through an activated carbon bed located downstream of the ultrafilter.

8. A method according to claim 1, wherein the method comprises a further step of treating water by reverse osmosis and/or a further step of treating water by electrodeionization, wherein the step of treating water by reverse osmosis and the step of treating water by electrodeionization are performed prior to the step of passing water through the ultrafilter.

9. A module comprising an ultrafilter and a mixed bed ion exchanger comprising beads having a pore size of 20-100 nm.

10. A module according to claim 9, wherein the ultrafilter comprises a hydrophilic ultrafiltration membrane.

11. A module according to claim 9, wherein the mixed bed ion exchanger is based on styrene divinylbenzene.

12. A module according to claim 9, wherein it further comprises an activated carbon bed.

13. A water treatment system for producing ultrapure water comprising an ultrafilter and a mixed bed ion exchanger comprising beads having a pore size of 20-100 nm, wherein the ultrafilter is located upstream of said mixed bed ion exchanger.

14. A water treatment system according to claim 13, wherein the ultrafilter and the mixed bed ion exchanger are provided in a single module comprising an ultrafilter and a mixed bed ion exchanger comprising beads having a pore size of 20-100 nm.

15. A water treatment system according to claim 13, wherein the ultrafilter and the mixed bed ion exchanger are provided in at least two modules.

16. A water treatment system according to claim 13, further comprising an activated carbon bed.

17. A method according to claim 1, wherein the method comprises a further step of passing water through an activated carbon bed located downstream of the ultrafilter and downstream of the mixed bed ion exchanger.

18. The module of claim 10, wherein the ultrafilter comprises a member from the group consisting essential of a hydrophobic vent membrane, one or more capillary tubes, and a bypass tube with a check valve.

19. A water treatment system according to claim 16, wherein the activated carbon bed is provided in a further module, comprising the activated carbon bed and optionally a mixed bed ion exchanger.

Description

FIGURES

[0099] FIG. 1 shows the experimental setup for simulating fouling conditions, as described in Example 1.

[0100] FIG. 2 shows the fouling resistance of different ion exchange resins by using artificial fouling water with humic acid (FIG. 2A) and artificial fouling water with alginic acid (FIG. 2B) according to Example 2.

[0101] FIG. 3 shows the protection of standard ion exchange resin by different purification media for humic acid (FIG. 3A) and alginic acid (FIG. 3B) according to Example 3.

[0102] FIG. 4 shows the effect of activated carbon according to Example 4.

[0103] FIG. 5 shows the experimental set-up for the test according to Example 5 (comparison of the use of a macroporous bead mixed bed resin and an ultrafiltration device with a state of the art solution).

[0104] FIG. 6 shows the cartridge configurations of the use of a macroporous mixed bed resin with an ultrafiltration module and prior art according to Example 5.

[0105] FIG. 7 shows the results according to Example 5.

EXAMPLES

Example 1: Experimental Setup for Simulating Fouling Conditions

[0106] For simulating fouling conditions in laboratory, humic acid (sodium salt, Sigma Aldrich) or sodium alginate (Sigma Aldrich) is spiked in water as model organic compound. The dirty DI (deionized) water is often ionically pure, thus its resistivity is at least 1 M.Math.cm, sometimes over 10 M.Math.cm. Although such water seems to be very pure, it may contain fouling matters which are not detectable by a resistivity meter. In the following experiments, simultaneous in-line injection of 100 to 400 ppb of humic acid or alginic acid or a mixture of both and NaCl equivalent to 1 M.Math.cm into pure water is used to prepare artificial fouling water to evaluate purification media and solutions:

[0107] Artificial fouling water is prepared by injecting a mixture of NaCl (Merck EMSURE) and humic acid (Sigma Aldrich) (concentration: 1 g/L NaCl, 0.24 g/L humic acid sodium salt) or a mixture of NaCl and sodium alginate (Sigma Aldrich) (concentration: 1 g/L NaCl, 0.24 g/L sodium alginate.) into water purified by an Elix 100 system (Merck KGaA, Darmstadt, Germany) and further deionized by a make-up polisher (Quantum TIX polishing cartridge, Merck KGaA, Darmstadt, Germany) with a precise injection pump (ISMATEC MCP-CPF process pump+PM0CKC pump head). The use of a defined ratio of NaCl/humic acid or alginate in the mixture allows for estimating the final concentration of humic acid or alginate by measuring the target conductivity of the artificial fouling water by a resistivity sensor (Thornton 770MAX) (R1): NaCl 406 ppb (=1 S/cm), humic acid 100 ppb; or NaCl 406 ppb, alginate 100 ppb. Several cartridges containing ion exchange resin beds, adsorptive media and/or filtration devices are placed in series. Intermediate and final water quality is checked by further resistivity sensors (R2 and R3) and an Anatel A100 TOC analyzer. The experimental setup is shown in FIG. 1.

Example 2: Fouling Resistance of Ion Exchange Resins

[0108] Different types of ion exchange resins alone are evaluated with the artificial fouling water. For this purpose mixed bed resins of 20 cm bed height are tested at 0.89 cm/s linear velocity with artificial fouling water with 100 ppb humic acid and 1 S/cm feed condition (A) or artificial fouling water with 100 ppb alginate and 1 S/cm feed condition (B), according to the experimental setup described in Example 1.

[0109] The following resins are tested (Table 1):

TABLE-US-00003 TABLE 1 Type Bead diameter Resin reference Standard Styrene 0.6-0.7 mm for Jetpore (used in resin divinylbenzene both anion and Milli-Q consumable gel type cation exchangers cartridge) (Merck KGaA) Asymmetric Styrene 0.6-0.7 mm for MR450UPW (DOW) resin divinylbenzene anion, 0.3-0.4 gel type mm for cation exchangers Macroporous Styrene 0.6-0.7 mm for IRN9882 (Rohm and resin divinylbenzene both anion and Haas) macroporous cation exchangers resin

[0110] The result for artificial fouling water with humic acid is shown in FIG. 2A: While the standard resin and the asymmetric resin shows immediate resistivity drop due to humic acid impact, the macroporous resin brings water resistivity higher.

[0111] The result for artificial fouling water with sodium alginate is shown in FIG. 2B:

[0112] Similar trends as described for humic acid are seen in the test.

Example 3: Protection of Standard Ion Exchange Resin by Different Purification Media

[0113] Since even the best resin is expected to have a limited capacity over time regarding fouling resistance, the following experiment is conducted in order to test its potential protection by other purification means.

[0114] For this purpose, in the experimental setup according to Example 1, different purification media are placed upstream of the standard ion exchange resin bed in order to compare their protection efficiency of the ion exchange resin against fouling matters.

[0115] The following purification media are tested:

Dead-End Filtration Media:

[0116] Hydrophilic PVDF membrane 0.22 m Merck, Millipak40, cat. no. MPGL04SK1 [0117] Hydrophobic PVDF membrane 0.65 m Merck, Millipak, cat. no. TANKMPK02 [0118] Hydrophilic PE hollow fiber membrane 0.1 m, Mitsubishi Rayon Sterapore, car. no. 40M0007HP [0119] Polysulfon hollow fiber UF 13K Dalton, Merck, Biopak, cat. no. CDUFBI001 [0120] Polysulfon hollow fiber UF 5K Dalton, Merck, Pyrogard 5000, cat. no. CDUFHF05K

Adsorption Media:

[0121] Natural coconut granular activated carbon, Jacobi carbon, cat. no. PICAHYDRO S 35 [0122] Synthetic spherical activated carbon, Kureha, cat. no. G-BAC [0123] Macroporous anion exchange resin, DOW, cat. no. IRA96SBC [0124] Diatomaceous sand filter, Merck Polygard CE, cat. no. CE02010506

[0125] Again, the tests are performed with artificial fouling water contaminated with humic acid (A) or artificial fouling water contaminated with alginate (B) according to the conditions described in Example 1.

[0126] The results are shown in FIG. 3.

[0127] In the tests performed with humic acid contaminated artificial fouling water the ultrafiltration media Polysulfon hollow fiber UF 13K Dalton and Polysulfon hollow fiber UF 5K Dalton perform the best in protecting the standard ion exchange resin.

[0128] In the tests with alginate contaminated artificial fouling water macroporous anion resin shows the best performance in protecting standard resin.

Example 4: Effect of Activated Carbon

[0129] Ultrafiltration media release significantly high TOC at start-up. It is assumed that the organic matters from UF are pure extractable portions from the membrane polymer, as well as solvent and additive from manufacturing processes. This experiment represents a simple rinsing test of the UF cartridge fed with Milli-Q water without fouling matter injection. The following setup is used: UF 13 kDa cartridge (Merck, Biopak, cat. no. CDUFBI001) followed by 20 cm standard ion exchange resin bed is fed by Milli-Q water at 0.5 L/min. To demonstrate TOC removal from UF extractable by activated carbon, 8 cm height of synthetic activated carbon (Kureha G-BAC) is placed between UF and resin bed.

[0130] The results are shown in FIG. 4: The addition of activated carbon results in a strong reduction of the initial TOC value and a further reduction of the TOC bottom level by a factor 2 after rinsing stabilization.

Example 5: Comparison of the Use of a Macroporous Bead Mixed Bed Resin and an Ultrafiltration Device with a State of the Art Solution

[0131] In the following test the combination of media is tested in lab scale ultrapure water production systems. FIG. 5 shows the experimental set up. The following configurations are compared (FIG. 6): [0132] State-of-the-art solution for treating fouling water: commercially available Milli-Q Advantage with Q-Gard T3, comprising a macroporous anion exchange resin and a macroporous mixed bed resin, combined with Quantum TEX Polishing Cartridge (Merck KGaA, Darmstadt, Germany), comprising a standard mixed bed ion exchange resin and synthetic activated carbon. [0133] Solution according to the present invention using a macroporous resin as defined above, with ultrafiltration means, and activated carbon.

[0134] Artificial fouling water with humic acid is used as described in Example 1. The results are shown in FIG. 7: The use of a macroporous resin bed with ultrafiltration means allows for a better performance regarding TOC content and resistivity as the state-of-the-art solution.