Sequestering uranium and technetium through co-precipitation with aluminum in a contaminated acidic environment.
This research evaluated a method of controlled base addition for immobilizing uranium (U) and technetium (Tc) through coprecipitation with aluminum (Al) and other metal ions which coexist in a highly contaminated acidic environment. The batch and column experiments indicate that the addition of strong base (NaOH) provided a rapid yet effective means of sequestering U, Tc, and toxic metal ions such as nickel (Ni2+) and cobalt (Co2+) in the sediment and groundwater. Greater than 94% of soluble U (as UO2(2+)) and > 83% of Tc (as TcO4-) can be immobilized at pH above 4.5 by co-precipitation with Al-oxyhydroxides. The presence of sediment minerals appeared to facilitate co-precipitation of these contaminants at lower pH values than those in the absence of sediments. The immobilized U and Tc were found to be stable against dissolution in Ca(NO3)2 solution (up to 50 mM) because of the formation of strong surface complexes between U or Tc and Al-oxyhydroxides. This research concludes that as long as a relatively high pH (> 5) and a low carbonate concentration are maintained, both U and Tc can be effectively immobilized under given site-specific conditions.
Luo
Wensui
W
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Kelly
Shelly D
SD
Kemner
Kenneth M
KM
Watson
David
D
Zhou
Jizhong
J
Jardine
Philip M
PM
Gu
Baohua
B
D000535:Aluminum / Q000737:chemistry*; D011232:Chemical Precipitation; D003035:Cobalt; D019015:Geologic Sediments; D006863:Hydrogen-Ion Concentration; D009532:Nickel / Q000737:chemistry; D013667:Technetium / Q000737:chemistry*; D014501:Uranium / Q000737:chemistry*; D014875:Water Pollutants, Radioactive / Q000737:chemistry*
D014875:Water Pollutants, Radioactive; D003035:Cobalt; D014501:Uranium; D013667:Technetium; D009532:Nickel; D000535:Aluminum