WaterSolutions Separation of Nitrogen from Liquid or Vapor

Potable 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 DOWEX™ 1 is recommended. If the ratio of sulfate to nitrate is high, a nitrate selective resin should be considered like DOWEX NSR-1 resin. The highest affinity for nitrate is achieved with DOWEX PSR-3, a Tributylamine, strong base, macroporous anion exchange resin. This high affinity comes at the cost of requiring more regenerant chemicals.

DOWEX resins, coupled with UPCORE™ process technology to minimize regenerant brine waste, provide an excellent way to address today's nitrate removal challenges.

If you have a commercial nitrate removal application, please Contact Us via the link on this page. Please include information about your particular nitrate removal application.

Waste Water: The common ionic forms of Nitrogen are the oxidized species of nitrate (NO(₃^-) and nitrite (NO₂^-) and the reduced species of ammonia (NH₄⁺). Other Nitrogen compounds such as amines, amino acids, and heterocyclic amines can be removed with ion exchange resins.

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 DOWEX M-43 resin, an acid absorber. When nitrate and nitrite are present as salts, they can be removed with a strong base Type I anion exchange resins like DOWEX 21K XLT and DOWEX 1 resins or strong base Type II anion exchange resins like DOWEX™ MARATHON™ A2 or DOWEX SAR resins according to their selectivity coefficients. Both Type I and 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 so it can be removed from air and liquids with a strong acid cation exchange resin or a weak acid cation exchange resin. A weak acid cation exchange resin like DOWEX MAC-3 cation exchange resin will only work when the ammonia is present as the free base, not a salt. Under these conditions, DOWEX MAC-3 resin is preferred due to its higher capacity and higher regeneration efficiency. When ammonia is present as a salt, a strong acid cation resin is needed to split the salt. Our product recommendation here is DOWEX G-26 (H) resin as a tough and versatile cation exchanger.

Primary, secondary and tertiary amines can be protonated to become cations which can be removed with a strong acid cation exchange resin 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.

Amino Acids and Peptides are a special focus for Dow so a section is devoted to this topic in the Biotech / Pharma and Fine Chemicals.

Gas: Since N₂ gas is often used in a compressed form, it is often contaminated with compressor lubricants. DOWEX™ OPTIPORE™ Polymeric Adsorbents have been shown to work well to remove these compressor lubricants from compressed gas streams. For more information, please go to VOC Control with Polymeric Adsorbents.

References

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