Chromatographic separation of platinum group metals from simulated high level liquid waste using macroporous silica-based adsorbents.
To separate platinum group metals (PGMs) from high level liquid waste, three novel macroporous silica-based adsorbents, namely, (Crea+Dodec)/SiO2-P, (Crea+TOA)/SiO2-P and (MOTDGA+TOA)/SiO2-P, were synthesized by introducing extractants Crea (N',N'-di-n-hexyl-thiodiglycolamide), TOA (Tri-n-octylamine), MOTDGA (N,N'-dimethyl-N,N'-di-n-octyl-thiodiglycolamide) along with theirs modifier, Dodec (n-dodecyl alcohol), into 50μm diameter SiO2-P particles by impregnation. Chromatographic separation of PGMs from simulated high level liquid waste was investigated by column method. It was found that 100% of Pd(II) and Re(VII) could be eluted out from simulate HLLW in 3.0M HNO3 solution using three adsorbents. For Ru(III) and Rh(III), high temperature has distinct effect on the adsorption rate and a further study for Ru(III) and Rh(III) is necessary to separate them from HLLW completely. In all six column experiments, a relatively satisfactory chromatographic separation operating for PGMs from simulated HLLW was obtained using (Crea+TOA)/SiO2-P adsorbent packed column at 323K.
Separation of Palladium along with Minor Actinides by isoBu-BTP/SiO2-P Adsorbent from High-Level Liquid Waste
Aiming at the separation of Pd(II) along with MA(III) from high-level liquid waste, a porous silica based adsorbent isoBu-BTP/SiO2-P was prepared. The adsorption properties of isoBu-BTP/SiO2-P toward Pd(II) were investigated. It was found that with the increase of HNO3 concentration, Pd(II) adsorption ability increased initially as HNO3 concentration increased until 1 M, then remained unchanged as HNO3 concentration further increased. The adsorption kinetics and isotherm of Pd(II) onto isoBu-BTP/SiO2-P fit well with the pseudo-second-order rate law and Langmuir adsorption model, respectively. The adsorption thermodynamic parameters revealed that the adsorption process was spontaneous and endothermic. A hot test utilizing isoBu-BTP/SiO2-P packed column was conducted and the simultaneous separation of Pd(II) and MA(III) was achieved from solution by using 0.01 M HNO3-0.1 M TU and 0.01 M HNO3-0.01 M DTPA as eluents, respectively. The Pd(II) with isoBu-BTP/SiO2-P complex was illustrated to be 1:1 type by HRMS...
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.