Agent and Process for Increasing Rejection of Nanofiltration Membrane or Reverse Osmosis Membrane, Nanofiltration Membrane or Reverse Osmosis Membrane, Process for Water Treatment and Apparatus for Water Treatment

• US 20090266764A1
• Filed: 03/23/2007
• Published: 10/29/2009
• Est. Priority Date: 03/29/2006
• Status: Abandoned Application

• Current Assignee: Kurita Water Industries Limited
• Original Assignee: Kurita Water Industries Limited
• Inventors: Kawakatsu, Takahiro
• Application Number:
  US12/225,604
• Publication Number:
  US 20090266764A1
• Time in Patent Office: Days
• US Class Current: 210/653
• CPC Class Codes: B01D 2325/20 Specific permeability or cut-off range
• CPC Class Codes: B01D 2325/34 Molecular weight or degree of polymerisation
• CPC Class Codes: B01D 61/025 Reverse osmosis; Hyperfiltration
• CPC Class Codes: B01D 61/027 Nanofiltration
• CPC Class Codes: B01D 67/0088 Physical treatment with compounds, e.g. swelling, coating or impregnation
• CPC Class Codes: C02F 1/44 by dialysis, osmosis or reverse osmosis general membrane separation processes B01D61/00, membrane modules B01D63/00, electrodialysis C02F1/4693, combination of membrane modules and bioreactors C02F3/1268
• CPC Class Codes: C02F 1/441 by reverse osmosis
• CPC Class Codes: C02F 1/442 by nanofiltration

Abstract

An agent for increasing the rejection of a nanofiltration membrane or a reverse osmosis membrane which comprises a compound having a polyalkylene glycol chain having a weight-average molecular weight of 2,000 to 6,000; a process for increasing the rejection of a nanofiltration membrane or a reverse osmosis membrane which comprises bringing the nanofiltration membrane or the reverse osmosis membrane into contact with an aqueous solution of a compound having a polyalkylene glycol chain which is obtained by diluting the agent for increasing the rejection of a nanofiltration membrane or a reverse osmosis membrane described above with water; a nanofiltration membrane or a reverse osmosis membrane exhibiting a rejection increased in accordance with the process; and a process and an apparatus for water treatment using the nanofiltration membrane or the reverse osmosis membrane. The rejection and, in particular, the rejection to nonionic solutes, of a nanofiltration membrane or a reverse osmosis membrane can be increased while the flux is kept at a great value.

Claims

1. An agent for increasing rejection of a nanofiltration membrane or a reverse osmosis membrane which comprises a compound having a polyalkylene glycol chain having a weight-average molecular weight of 2,000 to 6,000.

2. The agent for increasing rejection of a nanofiltration membrane or a reverse osmosis membrane according to claim 1, wherein the polyalkylene glycol chain has an ionic group introduced therein.

3. The agent for increasing rejection of a nanofiltration membrane or a reverse osmosis membrane according to claim 1, wherein the polyalkylene glycol chain is a polyethylene glycol chain.

4. The agent for increasing rejection of a nanofiltration membrane or a reverse osmosis membrane according to claim 1, which comprises a tracer for confirming rejection comprising an inorganic electrolyte or an organic compound soluble in water.

5. A process for increasing rejection of a nanofiltration membrane or a reverse osmosis membrane which comprises bringing the nanofiltration membrane or the reverse osmosis membrane into contact with an aqueous solution of a compound having a polyalkylene glycol chain which is obtained by diluting the agent for increasing rejection of a nanofiltration membrane or a reverse osmosis membrane described in claim 1 with water.

6. A nanofiltration membrane or a reverse osmosis membrane exhibiting a rejection increased by bringing the nanofiltration membrane or the reverse osmosis membrane into contact with an aqueous solution of a compound having a polyalkylene glycol chain which is obtained by diluting the agent for increasing rejection of a nanofiltration membrane or a reverse osmosis membrane described in claim 1 with water.

7. A process for water treatment which comprises treating water to be treated using a nanofiltration membrane or a reverse osmosis membrane exhibiting a rejection increased by bringing the nanofiltration membrane or the reverse osmosis membrane into contact with an aqueous solution of a compound having a polyalkylene glycol chain which is obtained by diluting the agent for increasing rejection of a nanofiltration membrane or a reverse osmosis membrane described in claim 1 with water.

8. A process for water treatment which comprises, using at least two membrane modules, passing water to be treated through a first membrane module and treating at least a portion of obtained concentrated water by a second membrane module, wherein the first membrane module and/or the second membrane module is a membrane module using a nanofiltration membrane or a reverse osmosis membrane exhibiting a rejection increased by bringing the nanofiltration membrane or the reverse osmosis membrane into contact with an aqueous solution of a compound having a polyalkylene glycol chain which is obtained by diluting the agent for increasing rejection of a nanofiltration membrane or a reverse osmosis membrane described in claim 1 with water.

9. The process for water treatment according to claim 7, wherein the water to be treated comprises boron in an amount of 3 to 8 mgB/liter.

10. An apparatus for water treatment which comprises a nanofiltration membrane or a reverse osmosis membrane exhibiting a rejection increased by bringing the nanofiltration membrane or the reverse osmosis membrane into contact with an aqueous solution of a compound having a polyalkylene glycol chain which is obtained by diluting the agent for increasing rejection of a nanofiltration membrane or a reverse osmosis membrane described in claim 1 with water.

11. An apparatus for water treatment which comprises at least two membrane modules, a second membrane module being connected to a side of concentrated water of a first membrane module, wherein the first membrane module and/or the second membrane module is a membrane module using a nanofiltration membrane or a reverse osmosis membrane exhibiting a rejection increased by bringing the nanofiltration membrane or the reverse osmosis membrane into contact with an aqueous solution of a compound having a polyalkylene glycol chain which is obtained by diluting the agent for increasing rejection of a nanofiltration membrane or a reverse osmosis membrane described in claim 1 with water.