WaterSolutions Separation of Heavy Metals from Water, Wastewater and Acids

Potable Water: Heavy metals can be removed from neutral pH water as cations. A weak acid cation exchange resin like DOWEX™ MAC-3 is a good choice due to its high capacity and ease of regeneration. A second option is a strong acid cation exchange resin like DOWEX MARATHON™ C (Na). Both resins can be brine regenerated or disposed of in accordance with local requirements once they are loaded with metals.

These resins meet NSF / ANSI Standard 61 for contact with drinking water. For more information see our regulatory information.

Acid and Wastewater: In HCl, all of these metals can form anions that can be removed with anion exchange resins. Ga, Ge, Sn (II), and Sb (III) form stronger anionic complexes (43KB PDF) with higher acid concentrations. Cd (II), Ir (II), Sn (IV), Sb (V), Tl (III), Pb (II), and Bi (III) form their strongest anionic complexes under mildly acidic conditions and in some cases can be eluted with strong HCl. Anions are effectively removed from solution with a strong base 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. A weak base anion exchange resin like DOWEX M-43 resin should also be evaluated to take advantage of this resins higher capacity and ease of regeneration.

In HCl, few of these metals will form cations that can be captured with a cation exchange resin. Most will form very weak cations in very dilute acid. In these cases, a weak acid cation exchange resin like DOWEX MAC-3 resin should be considered. Ga (III) is the exception, forming a cation in acid that can be removed with DOWEX M-31 and DOWEX MONOSPHERE™ M-31 catalysts.

Many of these metals can be more selectively removed from solution with chelating resins like the iminodiacetic acid resin, AMBERLITE™ IRC748i.

References

"Uptake of Heavy Metals by Chelating Resins from Acidic Manganese Chloride Solution" by Claudia Villa Diniz, Afonso Henriques Martins, and Fiona M. Doyle, Minerals and Metallurgical Processing, 17 (4) (2000) pp. 217-222.

"Resin Selectivity in Dilute to concentrated Aqueous Solutions" by R.M. Diamond and D.C. Whitney, Chapter 8 of Ion Exchange, A Series of Advances Edited by J.A. Marinsky, Published by Marcel Dekker, Inc., New York (1966).