Potable Water: Chrome contamination of drinking water usually takes the form of Cr (III) or Cr (VI) (also known as hexchrome). Cr (VI) is an anion so it can be selectively removed from drinking water with DOWEX™ 1 for high selectivity and loading capacity. Because of very strong binding of Chrome, it can be difficult to regenerate. DOWEX SAR is a Type II strong base anion exchange resin so it is more easily regenerated and has a lower odor potential. If you have a commercial chromium removal application, please Contact Us via the link on this page. Please include information about your particular chromium removal application.
DOWEX 1 and DOWEX SAR are NSF/ANSI Standard 61 compliant. For more information see our regulatory information.
Groundwater: Today, there are several industrial scale chromate-from-groundwater ion exchange resin installations operating. Chromate concentrations in groundwater, as low as 40 ppb, can be economically and effectively remediated using Dow's high performance anion exchangers, such as DOWEX 21K XLT resin. Regeneration is generally done off-site by a licensed contractor utilizing a sodium hydroxide / brine elution technique.
Plating: While a large portion of the world's bright chrome plating is carried out using chromium (VI) salts, a relatively small amount employs chromium (III). Many of the chromium (VI) operations employ a strong base anion exchange resin like DOWEX 21K XLT resin for wastewater purification. Loading Cr (VI) ions onto these resins is usually very high, sometimes greater than 8 lbs of metal per cubic foot of resin (128 g/L resin). Elution is usually accomplished with briny sodium hydroxide solution. Recovery of Cr (III) ions, however, usually requires the use of stronger weak acid cation exchange resin (see below).
Most of the trivalent chrome plating facilities depend heavily on ion exchange resins for smooth and economical operation, but not for the recovery of the Cr (III) ion. In these systems, copper is a problem-metal for the plating operation, adversely affecting the quality of the chromium plate. The distinct ability of DOWEX M4195 chelating resin to selectively adsorb copper (II) ions from strongly acidic media, makes it a perfect match for this particular application. Several plating technology supply houses are offering "strap-on" copper removal systems employing DOWEX M4195 chelating resin.
Wastewater: Chrome removal from water via ion exchange is common in chemical, petrochemical, oil refining, semiconductor manufacturing and power utility plants. In waters with low levels of Cr (III) and Cr (VI), strongly acidic cation exchange resins such as DOWEX G-26 (H) cation exchange resin are employed. Weak acid cation exchange resins such as DOWEX MAC-3 resin often provide high capacity and good multi-valent ion selectivity. In more brackish waters, 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 such as sodium and potassium.
|Chromium - Cr
Chromium is commonly found in process and waste solutions in either the Cr (III) or the Cr (VI) oxidation states. In general, the Cr (VI) ionic forms are anionic in character, such as: HCrO4-, CrO4-2, and Cr2O7-2 chromate complexes.