title: Sorption and binary exchange of nitrate, sulfate, and uranium on an anion-exchange resin.
abstract: Competitive ion-exchange reactions were studied on a strong-base anion-exchange resin to remove NO3- and uranium from a contaminated groundwater containing high levels of NO3- (approximately 140 mM), SO4(2-) (approximately 10 mM), and U(VI) (approximately 0.2 mM). Results indicate that although SO4(2-) carries divalent negative charges, it showed the least selectivity for sorption by the Purolite A-520E resin, which is functionalized with triethylamine exchange sites. Nitrate was the most strongly sorbed. Sorption selectivity followed the order of NO3- > Cl- > SO4(2-) under the experimental conditions. Nitrate competitively sorbed and displaced previously sorbed SO4(2-) in a column flow-through experiment and resulted in a high elution front of SO4(2-) in the effluent. Although the concentration of uranium in groundwater is orders of magnitude lower than that of NO3- or SO4(2-), it was found to be strongly sorbed by the anion-exchange resin. Because the most stable uranium species in oxic and suboxic environments is the UO2(2+) cation, its strong sorption by anion-exchange resins is hypothesized to be the result of the co-ion effect of NO3- by forming anionic UO2(NO3)3- complexes in the resin matrix. These observations point out a potential alternative remediation strategy that uses strong-base anion-exchange resins to remove uranium from this site-specific groundwater, which has a low pH and a relatively high NO3- concentration.
authors.affiliation: Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6036, USA. b26@ornl.gov
authors.forename: Baohua
authors.initials: B
authors.lastname: Gu
authors.forename: Yee-Kyoung
authors.initials: YK
authors.lastname: Ku
authors.forename: Philip M
authors.initials: PM
authors.lastname: Jardine
mesh_terms: D000327:Adsorption; D006863:Hydrogen-Ion Concentration; D007475:Ion Exchange Resins / Q000737:chemistry*; D009566:Nitrates / Q000737:chemistry / Q000302:isolation & purification*; D012990:Soil Pollutants, Radioactive / Q000302:isolation & purification*; D013431:Sulfates / Q000737:chemistry / Q000302:isolation & purification*; D013696:Temperature; D014501:Uranium / Q000737:chemistry / Q000302:isolation & purification*; D014875:Water Pollutants, Radioactive / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*
chemical_list: D007475:Ion Exchange Resins; D009566:Nitrates; D012990:Soil Pollutants, Radioactive; D013431:Sulfates; D014875:Water Pollutants, Radioactive; D014501:Uranium