Geochemical modeling of reactions and partitioning of trace metals and radionuclides during titration of contaminated acidic sediments

Journal Article · Tue Jan 01 04:00:00 EST 2008 · Environmental Science & Technology

DOI:https://doi.org/10.1021/es800311m· OSTI ID:985267

Zhang, Fan ^[1]; Parker, Jack C. ^[2]; Brooks, Scott C ^[1]; Watson, David B ^[1]; Jardine, Philip M ^[1]; Gu, Baohua ^[1]

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1. ORNL
2. University of Tennessee, Knoxville (UTK)

This study investigated sorption of uranium and technetium onto aluminum and iron hydroxides during titration of a contaminated groundwater using both Na hydroxide and carbonate as titrants. The contaminated groundwater has a low pH of 3.8 and high concentrations of NO3-, SO42-, Al, Ca, Mg, Mn, trace metals such as Ni and Co, and radionuclides such as U and Tc. During titration, most Al and Fe were precipitated out at pH above ~4.5. U as well as Tc was found to be removed from aqueous phase at pH below ~5.5, but to some extent released at higher pH values. An earlier geochemical equilibrium reaction path model that considered aqueous complexation and precipitation/dissolution reactions predicted mineral precipitation and adequately described concentration variations of Al, Fe and some other metal cations, but failed to predict sulfate, U and Tc concentrations during titration. Previous studies have shown that Fe- and Al-oxyhydroxides strongly sorb dissolved sulfate, U and Tc species. Therefore, an anion exchange model was developed for the sorption of sulfate, U and Tc onto Al and Fe hydroxides. With the additional consideration of the anion exchange reactions, concentration profiles of sulfate, U and Tc were more accurately predicted. Results of this study indicate that consideration of complex reactions such as sorption/desorption on mixed mineral phases, in addition to hydrolysis and precipitation, could improve the prediction of various contaminants during pre- and post-groundwater treatment practices.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 985267
• Journal Information: Environmental Science & Technology, Journal Name: Environmental Science & Technology Journal Issue: 10 Vol. 42; ISSN 1520-5851; ISSN 0013-936X
• Country of Publication: United States
• Language: English