Separation of Nitrogen from Liquid or Vapor

7

N

Drinking Water

Nitrate and nitrite are the more common nitrogen contaminants of drinking water. Since anion exchange resins are generally more selective for sulfate over nitrate, the capacity of a resin for nitrate removal will be limited by the concentration of sulfate. If the ratio of sulfate to nitrate is low, a high capacity resin like AMBERLITE™ PWA15 Resin is recommended. If the ratio of sulfate to nitrate is high, Dow’s nitrate-selective AMBERLITE PWA5 Resin should be considered.

Reverse-flow, packed bed systems are recommended for nitrate removal. These systems yield lower nitrate leakage, lower waste volume and the most efficient regeneration. UPCORE™ and AMBERPACK™ Packed Bed Systems,combined with AMBERLITE Resins, provide an excellent solution for nitrate removal challenges.

These resins may be subject to drinking water application restrictions in some countries. Please check the application status before use and sale.

Wastewater

Nitrate and nitrite are anions that can be removed with an anion exchange resin. When these anions are present as acids, they can be most efficiently removed from solution with a weak base anion exchange resin like AMBERLYST™ A21 Resin, an acid absorber. When nitrate and nitrite are present as salts, they can be removed with a strong base Type I anion exchanger like DOWEX™ 21K XLT Resin or with a strong base Type II anion exchanger like DOWEX MARATHON™ A2 Resin. Both Type I and Type II anion resins can strip nitrates from a stream, but the Type II resin is easier to elute and regenerate than the Type I resin. Regeneration for a Type II resin in this application can be accomplished using a brine solution.

Ammonia acts like a cation when it is protonated; therefore, it can be removed from air and liquids with a strong acid cation exchange resin or a weak acid cation exchange resin. When ammonia is present as the free base, a weak acid cation exchanger like DOWEX™ MAC 3 Resin is preferred due to its higher capacity and higher regeneration efficiency. But a weak acid cation resin will only work when the ammonia is present as the free base; if it is present as a salt, a strong acid cation resin is needed to split the salt. DOWEX G 26 (H) Resin is a tough and versatile strong acid cation exchanger.

Primary, secondary and tertiary amines can be protonated to become cations which can be removed with a strong acid cation exchanger like DOWEX™ G 26 (H) Resin, but it must be used in the H form.

Quaternary amines are already cationic and readily removed with DOWEX™ G 26 (H) Resin. Heterocyclic amines can be similarly treated.

Removing Lubricants from Compressed Gases

Since N2 gas is often used in a compressed form, it may be contaminated with compressor lubricants.

DOWEX OPTIPORE™ V493 Polymeric Adsorbent has been shown to work well to remove these compressor lubricants from compressed gas streams1 and DOWEX OPTIPORE V503 Polymeric Adsorbent could also be tested for comparison.

1 "Removal of oil from compressed gas with macroporous polymeric adsorbents" by Bowman, R.H. and Goltz, H.R. US Patent 5,700,310, MG Generon, December 23, 1997.

Elemental nitrogen, as the gas, makes up more than 78% of the Earth's atmosphere. Nitrogen is also the primary building block for several classes of chemical compounds that can be manipulated with ion exchange resins. In industry, nitrogen plays its largest role in the form of ammonia, which is the feedstock for the production of many useful compounds such as nitric acid, the nitrates, and thiocyanates.