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Method for inhibiting scale formation and/or dispersing iron in reverse osmosis systems

  • US 5,256,303 A
  • Filed: 07/20/1992
  • Issued: 10/26/1993
  • Est. Priority Date: 07/20/1992
  • Status: Expired due to Term
First Claim
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1. A method for inhibiting calcium sulfate scale formation and deposition from a feedstream passing through a reverse osmosis system which comprises the steps of:

  • a. controlling the pH of said feedstream within the range between about 6.0 to about 7.0;

    b. controlling the temperature of said feedstream within the range between about 50°

    to about 80°

    F.; and

    c. adding a scale inhibitor to said feedstream in an amount between about 0.002 ppm per ppm hardness (as CaCo3) of said feedstream to about 0.005 ppm per ppm hardness (as CaCO3) of said feedstream, said scale inhibitor comprising a water-soluble organic phosphonate which comprises a 2-phosphonobutane-1,2,4-tricarboxylic acid and a 1-hydroxyethane-1,1-diphosphonic acid, and an N-substituted acrylamide polymer containing an amide structure as follows;

    ##STR4## where R2 is hydrogen or methyl, R1 is a hydrogen or an alkyl, and R is alkylene or phenylene and X is sulfonate, (poly) hydroxyl, (poly) carboxyl or carbonyl, and combinations thereof, with the weight ratio of polymer to phosphonate being within the range of about 0.2;

    1 to about 2;

    1.

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