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Methods and apparatus for osmotic distillation

  • US 5,824,223 A
  • Filed: 11/08/1995
  • Issued: 10/20/1998
  • Est. Priority Date: 11/08/1995
  • Status: Expired due to Fees
First Claim
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1. A method of osmotic distillation for the concentration of a sample of relatively low osmotic pressure comprising:

  • providing a sample to be concentrated having first osmotic pressure;

    providing a solution having a higher osmotic pressure than said sample, said solution comprising a saturated or near-saturated aqueous solution containing one or more nonhalide salts, wherein said salts are chemically stable at temperatures up to the normal boiling point of the saturated solution of said salts, non-toxic to humans and animals, odorless and tasteless in aqueous solution, substantially incapable of forming precipitates when exposed to volatile components of feed solutions to be concentrated, non-corrosive to process equipment, and have large positive temperature coefficients of solubility in aqueous solution; and

    placing said sample and said solution on opposite sides of a hydrophobic microporous membrane;

    wherein said nonhalide salts are selected from the group consisting of tripotassium orthophosphate (K3 PO4), dipotassium monohydrogen orthophosphate (K2 HPO4), potassium dihydrogen orthophosphate (KH2 PO4), tetrapotassium pyrophosphate (K4 P2 O7), tripotassium monohydrogen pyrophosphate (K3 HP2 O7), dipotassium dihydrogen pyrophosphate (K2 H2 P2 O7), monopotassium trihydrogen pyrophosphate (KH3 P2 O7), and blends thereof.

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