DOWEX Resins for Separation of Arsenic from Liquid Media

Arsenic - As Arsenic is commonly found as the oxidized species of arsenate As(V) and arsenite As(III). The current US EPA standard for drinking water is 50 ppb.

Applications

Water / Wastewater: Arsenate, As (V), is an anionic species so it can be removed from solutions with a strong base anion exchange resin like DOWEX™ 21K XLT resin. For streams that have a high organic content and are prone to surface fouling DOWEX MARATHON™ MSA resin is recommended. Unfortunately, arsenate is very weakly ionic so it is not selectively removed and resin capacity will be limited in the presence of the other anions. Arsenate can also be removed with reverse osmosis membranes.

Arsenite is a neutral species so it needs to be further oxidized to arsenate for removal as described above. Oxidation can be accomplished by air stripping the water stream or addition of an oxidizing agent like peroxide or ozonolysis.

Selective Removal: Arsenic removal is also reported with immobilized metals on a variety of ion exchange supports. Chanda (1), reports using the ferric ion form of DOWEX M4195 chelating resin to remove arsenic from solution. Chanda (2), similarly reports the use of iminodiacetic acid chelating / selective resins in the ferric ion form for this same purpose. Ramana (3), reports using DOWEX M4195 chelating resin in the copper form.

Drinking Water: At this time, Dow can not recommend our DOWEX ion exchange resins for removal of arsenic from drinking water. Strong base anion exchange resins have been shown to remove sulfate, arsenate, and carbonate, all of which can be eluted with brine (chloride). Arsenate is weakly held and is easily displaced by competing anions. Under certain conditions this weak interaction may result in effluents having extremely high arsenate levels as arsenate is displaced by competing anions. Currently there are no sensors that can measure the arsenate breakthrough and switch a system into regeneration mode, preventing high concentrations of arsenic from potentially ending up in the produced drinking water. Because of these current equipment shortcomings, Dow does not support the use of our ion exchange resins for use in removal of arsenic for drinking water applications.

Information on the new ADSORBSIA* titanium-based arsenic removal media.

DOWEX Ion Exchange Resins

Product	Description	Type	Matrix	Total Exchange Capacity* eq/l (kgr/ft3)	Available Forms
DOWEX 21K XLT	Uniform particle size, high capacity, strong base anion exchange resin for mineral processing applications.	Type I Strong Base Anion	Styrene-DVB, Gel	1.4	Cl-
DOWEX MARATHON MSA	Uniform particle size, high capacity, macroporous strong base anion exchange resin for water demineralization applications.	Type I Strong Base Anion	Styrene-DVB, Macroporous	1.1 (24.0)	Cl-
DOWEX M4195	Chelating resin for copper, nickel, and cobalt processing.	Chelating Resin	Styrene-DVB, Macroporous		Bis-Picolylamine

References 1. "Ligand Exchange Sorption of Arsenate and Arsenite anions by chelating resins in ferric ion form. I. Weak-base chelating resin DOWEX XFS-4195." Chanda, M.; O'Driscoll, K.F.; Rempel, G.L., Reactive Polymers, 7, 251-61 (1998). 2. "Ligand Exchange Sorption of Arsenate and Arsenite anions by chelating resins in ferric ion form. II. Iminodiacetic chelating resin CHELEX 100." Chanda, M.; O'Driscoll, K.F.; Rempel, G.L., Reactive Polymers, 8, 85-95 (1998). 3. "Removing selenium(IV) and arsenic(V) oxyanions with tailored chelating polymers. " Ramana, Anuradha; Sengupta, Arup K.. ERM Inc., Exton, PA, USA. J. Environ. Eng. (N. Y.) (1992), 118(5), 755-75.