Purification of Noble Gases

9

F

Fluorine

Potable Water

Fluoride is a very low-selectivity anion so it cannot be removed from water without first removing all of the higher-selectivity anions like chloride or sulfate. Anions are removed according to their selectivity as described in the table of selectivity data.

Fluoride can be selectively removed with activated alumina. There are many suppliers available for this media.



Wastewater

Under acidic conditions, fluoride is present as HF and can be removed from solution with an acid absorber like AMBERLYST™ A21 Resin. Under neutral to basic conditions, DOWEX™ 21K XLT Resin has the strong base functionality needed to split the salt. For streams that have a high content of organic material and are prone to surface fouling, DOWEX MARATHON™ MSA Strong Base Anion Exchange Resin is recommended. Anions are removed according to their selectivity as described in the table of selectivity data.



Acid Gas Capture

Halogen acid gases cause corrosion problems in a wide variety of applications. AMBERLYST™ A21 Macroporous Weak Base Anion Resin can be used to remove the corrosive compounds.



17

Cl

Chlorine

Ground Water

Perchlorates (ClO4-) are man-made chemicals used in munitions and rocket propellants. They are highly soluble in water so they can be widely found in groundwater due to their high mobility. Once dispersed ClO4- can remain in the environment for decades as it does not readily degrade. DOWEX™ PSR-2 Resin can be used to bind and remove ClO4- at the ppb levels as a non-regenerated media.



53

I

Iodine

Salt Solutions

Selective iodine removal from salt solutions has been described using a metal hydroxide loaded ion exchange resin1. DOWEX™ G 26 (H) Strong Acid Cation Exchange Resin is a tough and versatile cation resin for this application.



Process Water/Wastewater

Under acidic conditions, halogens, and their complex oxides are acids and can be removed from solution with an acid absorber like AMBERLYST™ A21 Resin. Under neutral to basic conditions, DOWEX™ 21K XLT Resin has the strong base functionality needed to split the salt. For streams that have a high organic content and are prone to surface fouling, DOWEX MARATHON™ MSA Strong Base Anion Exchange Resin is recommended. Anions are removed according to their selectivity as described in the table of selectivity data.



Acid Vapor Capture

Halogen acid gases cause corrosion problems in a wide variety of applications. AMBERLYST™ A21 Macroporous Weak Base Anion Resin can be used to remove the corrosive compounds.



Removing Lubricants from Compressed Gasses

Since halogen gases (X2) are often used in a compressed form, they 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 streamsand DOWEX OPTIPORE V503 Polymeric Adsorbent could also be tested for comparison.



1 "Method of purification of salt solution for electrolysis", Oohara, C.; Matsuoka, T.; Kishi, T. and Okuno, T. of Chlorine Engineers Corp., Ltd. European Patent Application EP 0 987 221 A1 (1999).

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

The Group VIIA elements (fluorine, chlorine, bromine, iodine, astatine) are commonly referred to as halogens. Halogen atoms are characterized by an electronic structure where they are missing one electron so they readily form the anion X-. Halogens also form complexes like iodide (I3-) that are strongly anionic. Halogens form oxo-acids and oxides such as chlorite (ClO2-) and perchlorate (ClO4-) that are also anionic.