Separation of Phosphorus from Liquid Media

15

P

Water/Wastewater

The oxidized phosphates are anions so they can be removed from solutions with anion exchange resins.

If phosphates are present in acidic solutions, they can be removed with an acid absorber like AMBERLYST™ A21 Resin.

When phosphates are present as acid salts, a strong base anion exchanger like DOWEX™ 21K XLT Resin is recommended. Phosphates generally have a low affinity for Type II strong base anion exchange resins so they are typically not used.

For streams that have a high organic content and are prone to surface fouling, DOWEX MARATHON™ MSA Macroporous Resin is recommended.

Unfortunately, phosphates are very weakly selected so resin capacity will be limited in the presence of most other anions. See the table of selectivity data.

Selective Removal

Phosphates can be selectively removed from solution with DOWEX™ M4195 Chelating Resin in the copper form.1 2 Note that Dow Water & Process Solutions does not supply the resin in this form.

Phosphate Ester Lubricants

Phosphate esters are used as lubricants for a variety of industrial applications. During the course of their use, these lubricants break down and release phosphates that can be detrimental to the equipment and operations. AMBERLYST™ A21 Resin effectively removes the phosphates and many oxidative by-products from the lubricant. This anion resin must be used in the dry form to optimize performance in systems that are not water-miscible.3

A wide variety of organo-phosphorous compounds also exist that may or may not be ionic. When the organic group is small, anion exchange resins will work best. When the organic group is large, an adsorption approach may work best.

1 "Selective removal and recovery of phosphate using a new class of sorbents" by Zhao, Dongye; Sengupta, Arup K., Water Science Tech. Vol. 33 1996 Department of Civil and Environmental Engineering 13E Packer Avenue, Lehigh University, Bethlehem, PA 18015, U.S.A.

2 "Ultimate removal of phosphate from wastewater using a new class of polymeric ion exchangers" by Zhao, Dongye; Sengupta, Arup K., Dept. of Civil and Environmental Engineering, Lehigh University, Bethlehem, PA, USA. Water Res. (1998), 32(5), 1613-1625.

3 "Regeneration of Phosphate Ester Lubricating Fluids" by Dufresne, Peter, US Patent 5,661,117 August 26, 1997.

Phosphorus is found in many ionic forms. Some of the common ionic forms of phosphate are the oxidized species of phosphoric acid (H3PO4), phosphorous acid (H2PO3), and hypophosphorous acid (H3PO2), along with their salts.