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Production of purified water and high value chemicals from salt water

  • US 7,083,730 B2
  • Filed: 08/01/2003
  • Issued: 08/01/2006
  • Est. Priority Date: 08/02/2002
  • Status: Active Grant
First Claim
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1. A method of producing purified water and sodium chloride from salt water that contains sodium chloride, the method comprising:

  • feeding the salt water to a reverse osmosis unit;

    operating the reverse osmosis unit to separate the salt water into a permeate of purified water which is recovered and a retentate that contains sodium chloride that is concentrated with reference to the salt water;

    feeding the retentate to an electrodialysis unit having a plurality of membranes, wherein at least one electrodialysis membrane is a univalent anion-selective membrane and at least one other electrodialysis membrane is a univalent cation-selective membrane;

    operating the electrodialysis unit to separate the retentate into a diluate that is depleted in sodium chloride with reference to the retentate, and a concentrate that is concentrated in sodium chloride with reference to the retentate, wherein at least a portion of the diluate is recycled back to the feed to the reverse osmosis unit;

    feeding the concentrate to a salt-recovery unit; and

    operating the salt-recovery unit to recover sodium chloride from the concentrate.

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