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Bifunctional Anion Exchange Resin PilotEdwards AFB, CASource: Gu, Baohua, and G.M. Brown, 2000, "Efficient Removal of Perchlorate (ClO4-) From Contaminated Water by Highly Selective, Regenerable Bifunctional Resins" in Perchlorate Treatment Technology Workshop, 5th Annual Joint Services Pollution Prevention & Hazardous Waste Management Conference & Exhibition, August 21-24, 2000, Henry B. Gonzalez Convention Center, San Antonio, Texas. Project Summary: The following text was excerpted from Gu, Baohua, and G.M. Brown, 2000, "Efficient Removal of Perchlorate (ClO4-) From Contaminated Water by Highly Selective, Regenerable Bifunctional Resins" in Perchlorate Treatment Technology Workshop, 5th Annual Joint Services Pollution Prevention & Hazardous Waste Management Conference & Exhibition, August 21-24, 2000, Henry B. Gonzalez Convention Center, San Antonio, Texas. The Oak Ridge National Laboratory (ORNL) and University of Tennessee have recently developed a new class of bifunctional anion exchange resins (U.S. patent # 6,059,975), which are highly selective for sorption of ClO4- from contaminated groundwater or surface water. The bifunctional anion exchange resins were initially developed under DOE sponsorship for pertechnetate (TcO4-) removal at ppt levels. Perchlorate behaves similarly to pertechnetate, as both are large, poorly hydrated anions. The bifunctional resins consist of quaternary ammonium groups with both large (C6) and small (C2) alkyl groups resulting in high selectivity and good exchange kinetics. The field study utilized a flow rate of 2 bed volumes per minute, and influent perchlorate concentrations of about 50 ppb. The chemistry of the groundwater used in the field study was as follows: 7 mg/L chlorine, 0 mg/L fluorine, 61.2 mg/L nitrate, 14.9 mg/L sulfate, 98.6 mg/L bicarbonate, ~50 ug/L perchlorate, and pH 6.9. The bifuntional resin tested was D-3696, with trihexylamine/triethylamine functional groups, which is the Purolite International, Inc. scale-up version of the bifunctional resin synthesized at the University of Tennessee. The small-scale field experiment demonstrated that the bifunctional resin was able to treat ~110,000 bed volumes of groundwater in about 40 days before a 10% breakthrough of ClO4- occurred (running at ~2 bed volumes per minute with an initial ClO4- concentration of ~50 ug/L). The bifunctional resins are particularly effective in removing trace quantities of ClO4- in groundwater to below the detection limit (~3 ug/L). No pretreatment is needed to remove either dissolved organic matter or other competing anions (such as Cl-, SO42-, HCO3-, or NO3-), which may be present at 3-5 orders of magnitude higher than that of ClO4- in the groundwater or surface water. The treatment process does not involve addition or removal of unwanted organic or inorganic components in the water because of the high selectivity of the bifunctional resins. Additionally, a new regeneration technology (U.S. patent pending, 09/491,242) has been developed at ORNL so that these anion-exchange resins can be used repeatedly over a long-term operation. The regeneration process uses tetrachloroferrate (FeCl4-), is cost-effective and generates minimal amounts of secondary wastes. No decrease in resin performance after seven cycles of perchlorate loading and regeneration were noted, on tests with the D-3696 resin column (10 x 22 mm), with 17 BV/minute flow, and 10 mg/L initial perchlorate concentration. Therefore, the new resin and new regeneration technology offer a promising solution to remediate the ClO4-- contaminated groundwater or surface water by using either the conventional pump-and-treat or the funnel-and-gate treatment configurations (with regenerable treatment systems). Additional Info Source: Gu, Baohua, and G.M. Brown, 2000, "Efficient Removal of Perchlorate (ClO4-) From Contaminated Water by Highly Selective, Regenerable Bifunctional Resins" in Perchlorate Treatment Technology Workshop, 5th Annual Joint Services Pollution Prevention & Hazardous Waste Management Conference & Exhibition, August 21-24, 2000, Henry B. Gonzalez Convention Center, San Antonio, Texas. |
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