Processing Organic Solvents

Recovery or Removal of Metals from Organic Media

Ion exchange processes work just as well in non-aqueous organic streams as they do in water based systems. Many Dow customers use ion exchange resins for removal of acids and metal salts from organic solvents in applications such as color control (shelf life improvement) and precious metal catalyst recovery. To accomplish this, a few simple adjustments are required.

Most ion exchangers are normally delivered as a water wet product. Since water and organic solvents do not mix, an interface will exist at the water-solvent boundary that will inhibit ion mobility into an out of the resin beads. Drying the ion exchange resin will allow solvents to fully permeate the media so the chemistry is fully utilized.

Dow offers several dried cation exchange resins that are ready to use in organic solvent applications. These products are designated DOWEX™ DR-2030 catalyst and DOWEX MONOSPHERE™ DR-2030 catalyst.

Ion exchange resins can be dried in an oven at 95°C to 100°C (200°F to 212°F) or via chromatographic displacement using a dry, polar solvent (methanol, ethanol, isoproponol, acetone, etc.). For critical applications, where water must be completely excluded, it is wise to verify that the resin is dry using a Karl-Fisher titration. For details on drying resins, see our technical literature for Organic Solvent Dessicants. (30KB PDF)

When water is removed from ion exchange resins, they typically shrink in size. Care should be taken if they are re-hydrated as they will swell creating high pressures that can damage the resin beads and equipment.

Dehydrated beads are "tighter" or more kinetically inhibited. Ion exchange processes are therefore slower and longer contact times or slower flow rates may be required. Slower reaction kinetics can also be offset by using fine mesh resins. (183KB PDF)

Dry macroporous resins will contain air that will prevent contact between the resin and the solvent. The beads can be degassed by pulling a slight vacuum on the resin solvent mixture.