DOWEX Resins for Separation of Iron from Liquid Media

Iron - Fe Iron is the 4th most abundant element in the Earth's crust and is the basis for thousands of useful products from steel to medicine. Generally, ion exchange resins are not employed for the commercial bulk concentration and recovery of iron. Nevertheless, ion exchange resins are commonly used in the control of trace iron in drinking water and commercial process water.

Applications

Brine/HCl: Normally we think of ionic iron as a di- or tri-valent cation, which would be easily picked-up by standard cation exchange resins. While this is true, one of the most useful applications of ion exchange for iron removal employs anion exchange resin to capture Fe³⁺ (Ferric) ions as an anionic complex. Similar to zinc, this is possible because these metals form multivalent anionic complexes (42KB PDF) in the presence of excess chloride ion.

FeCl₃+ MCl   is at equilibrium with   M⁺FeCl₄^-

Purification of concentrated HCl is commonly carried out on a commercial scale. Interestingly, the resin is eluted with plain water. In the absence of excess halide ion the equilibrium shifts back to the left and the neutral salt "falls off of the resin". For more information, see page 6 of DOWEX™ Ion Exchange Resins – Powerful Chemical Processing Tools. (164K PDF)

Water/Wastewater: Iron removal from water via ion exchange is common in chemical and petrochemical processing, oil refining, semiconductor manufacturing and power utility plants. In waters with low levels of dissolved salts, a strongly acidic cation exchange resin such as DOWEX G-26 (H) cation exchange resin is employed. Weak acid cation exchange resins such as DOWEX MAC-3 resins often provide high capacity and good multi-valent ion selectivity. In more brackish waters, however, chelating resins may be required. Chelating resins have reactive units dispersed along their polymer matrix, each of which have multiple metal binding sites. Hence, chelating resins are selective for multi-valent cations over mono-valent cations like sodium and potassium.

DOWEX Ion Exchange Resins

Product	Description	Type	Matrix	Total Exchange Capacity* eq/l (kgr/ft3)	Available Forms
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 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 G-26 (H)	Uniform particle size strong acid cation exchange resin for specialty demineralization and catalyst applications.	Strong Acid Cation	Styrene-DVB, Gel	2.0	H+
DOWEX MAC-3	A macroporous weak acid cation exchange resin used for water softening, dealkalization, and demineralization applications.	Weak Acid Cation	Polyacrylic, Macroporous	3.8 (83.0)	H+