Separation of Heavy Metals from Water, Wastewater, and Acids
These metals—cadmium, lead, tin, gallium, germanium, indium, antimony, thallium, and bismuth—are grouped together as heavy metals due to common chemistry. The most common economic metals are cadmium, lead, and tin. Gallium, germanium, indium, antimony, bismuth and thallium are of less commercial interest and occurrence. These metals will form a wide variety of compounds that are cationic and anionic so a variety of different resins can be applied to their separation.
Heavy metals can be removed from neutral pH water as cations. A weak acid cation exchanger like AmberLite™ IRC83 H Resin is a good choice due to its high capacity and ease of regeneration. A second option is a strong acid cation exchanger like AmberLite™ HPR1100 Na Resin. Both resins can be regenerated with NaCl brine or disposed of in accordance with local requirements once they are loaded with metals.
These resins may be subject to drinking water application restrictions in some countries. Please check the application status before use and sale. For more information see our regulatory information.
Under certain conditions in HCl, all of these metals can form anionic complexes that can be removed with anion exchange resins.
Ga, Ge, Sn2+, and Sb3+ form stronger anionic complexes (43KB PDF) with higher acid concentrations.
Cd2+, In2+, Sn4+, Sb5+, Tl3+, Pb2+, and Bi3+ 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 AmberSep™ 21K XLT Resin. For streams that have a high organic content and are prone to surface fouling, AmberLite™ HPR9200 Cl Resin is recommended. A weak base anion exchanger like AmberLyst™ A21 Resin should also be evaluated to take advantage of this resin’s ease of regeneration.
In HCl, a 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 exchanger like AmberLite™ IRC83 H Resin should be considered. Ga3+ is the exception, forming a cation in acid that can be removed with AmberLyst 15 Dry Catalyst (standard) and AmberLyst 17 Catalyst (uniform particle size).
Many of these metals can be more selectively removed from solution with chelating resins like the iminodiacetic acid resin, AmberSep™ IRC748 Resin.
"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).