Efficient
and rapid removal of radioactive contaminants is crucial
when they are released into the environment following nuclear accidents.
Here, different types of apatite were synthesized using tributyl phosphate
(TBP) and tested for the removal of uranium from various solutions
using different reaction times and uranium concentrations. The uranium
adsorption results showed that uranium adsorption reached a steady
state within 24 h in tests open to atmosphere at a slightly alkaline
pH in different background solutions. TBP-coated hydroxyapatite removed
U better than hydroxyapatite alone did. The U removal mechanism was
considered as multilayer adsorption, showing the best fit to the Freundlich
isotherm. The maximal U adsorption capacity determined from the Langmuir
isotherm is 38 mg of U g–1. Because of the high
U removal efficiency, even at the high pH used in this study, TBP-coated
hydroxyapatite appears to be a promising adsorbent for the removal
of U from various waste streams as well as for recovery of U from
seawater.
AbstractBatch sorption and column experiments were conducted to investigate and compare sorption and transport behavior of 90Sr on the assumption of seawater intrusion at nuclear power plants. Batch sorption experiments were carried out on fractured rocks and bedrocks using synthetic groundwater and seawater both spiked with 90Sr. In general, higher 90Sr sorption occurred on fractured rock samples than on bedrocks, because of the presence of weathered secondary minerals (iron oxide and clay) on fractured rock surfaces. However, one particular bedrock sample (WSP-B) which has higher porosity and carbon amount than fractured rock samples also showed the higher 90Sr sorption than its comparable fractured rocks. For all batch sorption studies, 90Sr sorption distribution coefficient, Kd decreased from groundwater to seawater environment due to the higher ionic strength of seawater (6.4×10−1–7.7×10−1 M) compared to groundwater (4.0×10−3–6.0×10−3 M). The three different ionic strength solutions were used in column experiments, and the results showed that transport behavior of Sr through a fractured rock had similar sorption trend to batch sorption results. The highest mobility (or least retardation) for Sr was found for 100% seawater solution compared to the highest retardation (or least mobility) for 100% groundwater solution. These sorption and transport data of Sr on solid materials contacted with various ionic strength solutions corroborate empirically defensible information for assessment of radioactive contamination in groundwater below the NPP sites located nearby shores. In addition, the experimental data will be incorporated to improve transport models of 90Sr in the subsurface environment for severe nuclear accidents.
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