• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.1041-1046
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• 2019

In terms of long-term safety for radioactive waste disposal, the anionic iodide (I-129) with a long half-life ($1.6{\times}10^6yr$) is of a critical importance because this radionuclide migrates in geological media with limited interactions. Various studies have been performed to retard the iodide migration. Recently, some minerals that are likely generated from waste container corrosion, have been suggested to have a considerable chemical interaction with iodide. In this study, chalcocite and mackinawite were selected as candidate minerals for underground corrosion materials, and an iodide sorption experiment were carried out. The experiment was performed under anoxic and alkaline conditions and the pH effects on the iodide sorption were investigated in the range of pH 8 to 12. The results showed that both minerals demonstrated a noticeable sorption capacity on iodide, and the distribution coefficient ($K_d$) decreased as the pH increased in the experimental condition. In addition, when the alkalinity increased higher than a pH of 12, the sorption capacity of both minerals decreased dramatically, likely due to the competition of hydroxy ions with the iodide. This result confirmed that chalcocite was an especially good sorbing media for iodide under alkaline conditions with a pH value of less than 12.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.3
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• pp.235-243
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• 2006

In this study, an experimental study on the sorption properties of uranium(VI) onto a bentonite colloid generated from Gyeongju bentonite which is a potential buffer material in a high-level radioactive waste repository was performed as a function of the pH and the ionic strength. The bentonite colloid prepared by separating a colloidal fraction was mainly composed of montmorillonite. The concentration and the size fraction of the prepared bentonite colloid measured using a gravitational filtration method was about 5100 ppm and 200-450 nm in diameter, respectively. The amount of uranium removed by the sorption reaction bottle walls, by precipitation, and by ultrafiltration was analyzed by carrying out some blank tests. The removed amount of uranium was found not to be significant except the case of ultrafiltration at 0.001 M $NaClO_4$. The ultrafiltration was significant in the lower ionic strength of 0.001 M $NaClO_4$ due to the cationic sorption onto the ultrafilter by a surface charge reversion. The distribution coefficient $K_d$ (or pseudo-colloid formation constant) of uranium(VI) for the bentonite colloid was about $10^4{\sim}10^7mL/g$ depending upon pH and ionic strength of $NaClO_4$ and the $K_d$ was highest in the neutral pH around 6.5. It is noted that the sorption of uranium(VI) onto the bentonite colloid is closely related with aqueous species of uranium depending upon geochemical parameters such as pH, ionic strength, and carbonate concentration. As a consequence, the bentonite colloids generated from a bentonite buffer can mobilize the uranium(VI) as a colloidal form through geological media due to their high sorption capacity.

• Journal of Environmental Science International
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• v.19 no.5
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• pp.549-563
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• 2010

The environmental behaviors of polycyclic aromatic hydrocarbons (PAHs) are mainly governed by their solubility and partitioning properties on soil media in a subsurface system. In surfactant-enhanced remediation (SER) systems, surfactant plays a critical role in remediation. In this study, sorptive behaviors and partitioning of naphthalene in soils in the presence of surfactants were investigated. Silica and kaolin with low organic carbon contents and a natural soil with relatively higher organic carbon content were used as model sorbents. A nonionic surfactant, Triton X-100, was used to enhance dissolution of naphthalene. Sorption kinetics of naphthalene onto silica, kaolin and natural soil were investigated and analyzed using several kinetic models. The two compartment first-order kinetic model (TCFOKM) was fitted better than the other models. From the results of TCFOKM, the fast sorption coefficient of naphthalene ($k_1$) was in the order of silica > kaolin > natural soil, whereas the slow sorbing fraction ($k_2$) was in the reverse order. Sorption isotherms of naphthalene were linear with organic carbon content ($f_{oc}$) in soils, while those of Triton X-100 were nonlinear and correlated with CEC and BET surface area. Sorption of Triton X-100 was higher than that of naphthalene in all soils. The effectiveness of a SER system depends on the distribution coefficient ($K_D$) of naphthalene between mobile and immobile phases. In surfactant-sorbed soils, naphthalene was adsorbed onto the soil surface and also partitioned onto the sorbed surfactant. The partition coefficient ($K_D$) of naphthalene increased with surfactant concentration. However, the $K_D$ decreased as the surfactant concentration increased above CMC in all soils. This indicates that naphthalene was partitioned competitively onto both sorbed surfactants (immobile phase) and micelles (mobile phase). For the mineral soils such as silica and kaolin, naphthalene removal by mobile phase would be better than that by immobile phase because the distribution of naphthalene onto the micelles ($K_{mic}$) increased with the nonionic surfactant concentration (Triton X-100). For the natural soil with relatively higher organic carbon content, however, the naphthalene removal by immobile phase would be better than that by mobile phase, because a high amount of Triton X-100 could be sorbed onto the natural soil and the sorbed surfactant also could sorb the relatively higher amount of naphthalene.

• Membrane and Water Treatment
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• v.15 no.2
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• pp.67-78
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• 2024

In this study, a nickel hexacyanoferrate and manganese dioxide-polyacrylonitrile (NM-PAN) composite was synthesized and used for the sorptive removal of Co²⁺, Sr²⁺, and Cs⁺ Cs⁺ in radioactive laundry wastewater. Single- and multi-solute competitive sorptions onto NM-PAN were investigated. The Freundlich (Fr), Langmuir (Lang), Kargi-Ozmıhci (K-O), Koble-Corrigan (K-C), and Langmuir-Freundlich (Lang-Fr) models satisfactorily predicted all the single sorption data. The sorption isotherms were nonlinearly favorable (Freundlich coefficient, N_F = 0.385-0.426). Cs⁺ has the highest maximum sorption capacity (q_mL = 0.855 mmol g^-1) for NM-PAN compared to Co²⁺ and Sr²⁺, wherein the primary mechanism was the physical process (mainly ion-exchange). The competition between the metal ions in the binary and ternary systems reduced the respective sorption capacities. Binary and ternary sorption models, such as the ideal adsorbed solution theory (IAST) model coupled with single sorption models of IAST-Fr, IAST-K-O, IAST-K-C and IAST-Lang-Fr, were fitted to the experimental data; among these, the IAST-Freundlich model showed the most satisfactory prediction for the binary and ternary systems. The presence of cationic surfactants highly affected the sorption on NM-PAN due to the increase in distribution coefficients (K_d) of Co²⁺ and Cs⁺.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.239-247
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• 2005

In this study, an experimental study on the sorption properties of uranium(VI) onto bentonite colloids generated from a domestic calcium bentonite (called as Gyeongju bentonite). Gyeongju bentonite has been considered as a potential candidate buffer material in the Korean disposal concept for high-level radioactive wastes. The size and concentration of the bentonite colloids used in the sorption experiment were measured by a filtration method. The result showed that the concentration of the synthesized bentonite colloid suspension was 5100ppm and the size of the most of bentonite colloids(over $98\%$) was in the range of 200-450nm in diameter. The amount of uranium lost by the sorption onto bottle walls, by precipitation, and by ultrafiltration or colloid formation was analyzed by carrying out some blank tests. The loss of uranium by the ultrafiltration was significant in the lower ionic strength(i.e., in the case of 0.001M $NaClO_4$) due to the cationic sorption effect onto the ultrafilter by a surface charge reversion. The distribution coefficient (or pseudo-colloid formation constant) for the sorption of uranium(VI) onto bentonite colloids was $10^4^{\sim}10^6$ mL/g depending upon pH and the distribution coefficient was highest in the neutral pH around 6.5.

• Journal of Soil and Groundwater Environment
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• v.13 no.2
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• pp.21-29
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• 2008

Sorption and desorption processes play an important role in the transport and fate of organic contaminants in subsurface system. In this study, sorption and desorption characteristics of atrazine in 7 soils selected at the Gwangju area were investigated. Soil organic carbon contents ranged from 0.42 to 2.82%. Sorption and desorption experiments were performed in batch slurries. Sorption distribution coefficient ($K_d$) of atrazine were ranged from 0.48 to 3.26 l/kg and $K_d$ value increased with increasing organic carbon contents except of Kyongbang and Youngdong soils. Single desorption data were analyzed by the three-site desorption model including equilibrium, non-equilibrium and non-desorbable site. Non-desorbable site fractions of atrazine in all soils were enumerated and non-desorbable atrazine was observed in seriesdilution desorption experiment. Sorption/desorption hysteresis was also observed in the series-dilution desorption experiment.

• Nuclear Engineering and Technology
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• v.23 no.4
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• pp.410-419
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• 1991

Four domestic bentonite samples collected from the south-eastern area of Korea were identified as Ca-bentonite by analysing XRD-patterns and chemical compositions. By comparing the surface area, CEC and the swelling rate of these samples, Dong-Hae A was selected as a suitable sample for the investigation of distribution coefficients. Sorption equilibrium of Cs, Co and Am was reached in around 10 days, but that of Sr was found to be much earlier. From the measured distribution coefficients, the domestic bentonite was found to have high sorption capacity. In the effect of varying concentration on the distribution coefficient, the values of radionuclides peaked at about 10$^{-7}$ mo1/$\ell$ of concentration.

• Computers and Concrete
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• v.18 no.3
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• pp.367-388
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• 2016

In this paper, a simple practical method is introduced in which a simple weight measurement of concrete and finite element numerical analysis are used to determine the moisture transfer coefficient of concrete with a satisfactory accuracy. Six concrete mixtures with different water-to-cementitious material (w/cm) ratios and two pozzolanic materials including silica fume and zeolite were examined to validate the proposed method. The comparison between the distribution of the moisture content obtained from the model and the one from the experimental data during both the wetting and drying process properly validated the performance of the method.With the proposed method, it was also shown that the concrete moisture transfer coefficient considerably depends on the pore water saturation degree. The use of pozzolanic materials and also lowering w/cm ratio increased the moisture transfer coefficient during the initial sorption, and then, it significantly decreased with an increase in the water saturation degree.

• Journal of Korea Soil Environment Society
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• v.4 no.2
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• pp.77-86
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• 1999

Partitioning of two hydrophobic organic compounds (HOCs), phenanthrene and naphthalene, to kaolinite and sorbed surfactants was studied to evaluate the feasibility of surfactant-enhanced remediation (SER) of contaminated subsurface systems. Sorbed surfactant partition coefficients. $K_ss$, showed a strong dependence on the surfactant sorption isotherms at low sorbed surfactant levels $K_ss$ values were at their highest and then decreased with increasing surfactant sorption densities. $K_ss$ values for SDS were always larger than corresponding $K_mic$values. For Tween 80, however. $K_ss$ values $K_mic$ were higher than $K_mic$ values only at the lower sorbed surfactant densities. HOC distribution between immobile and mobile phases varied with surfactant dose distribution coefficients increased initially with increasing surfactant concentrations and then decreased at higher doses. This observation shows directly the competition between sorbed and micellar surfactants for HOC partitioning. Overall results of this study demonstrate that surfactant sorption to the solid phase can lead to increases in HOC retardation in some SER applications. Therefore, before an SER process is selected, appropriate consideration of surfactant sorption and HOC partitioning to immobile versus mobile phases pertinent to a specific subsurface system must be contemplated.

• Journal of Soil and Groundwater Environment
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• v.11 no.5
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• pp.1-8
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• 2006

The objective of this study is to assess impacts of sorption heterogeneity on the transport of leachate leaked from unlined landfill sites and is accomplished by examining the results from a series of Monte-Carlo simulations. For random distribution coefficient ($K_{d}$) fields with four different levels of heterogeneity ranging from homogeneous to highly heterogeneous, the transport of leachate was investigated by linking a saturated flow model with a contaminant transport model. Impacts of a chemical heterogeneity were evaluated using point statistics values such as mean, standard deviation, and coefficient of variation of the concentration obtained at monitoring wells from 100 Monte-Carlo trials. Inspection of point statistics shows that the distribution of distribution coefficient in the landfill site proves to be an important parameter in controlling leachate concentrations. In comparison to homogeneous sorption, heterogeneous $K_{d^-}$ fields produce the variability in the leachate concentration for different realizations. The variability increases significantly as the variance in the $K_{d^-}$ field and the travel time between source and monitoring well increase. These outcomes indicate that use of a constant homogeneous $K_{d}$ value for predicting the transport of leachate can result in significant error, especially when variability in $K_{d}$ is high.