• Environmental Engineering Research
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• v.10 no.6
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• pp.294-305
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• 2005

The effectiveness of fly ash-, quicklime-, and quicklime-fly ash-based stabilization/solidification(S/S) in chromium(Cr) contaminated soils was investigated using modified semi-dynamic leaching tests. Artificial soil samples composed of kaolinite or montmorillonite contaminated with chromium nitrate(4000 mg $Cr^{3+}\;kg^{-1}$ of solid) were prepared and then subjected to S/S treatment using quicklime, fly ash, or quick lime-fly ash. The effectiveness of the treatment was evaluated by assessing the cumulative fraction of leached $Cr^{3+}$ as well as, by computing the effective diffusivity ($D_e$) and the leachability index (LX) of the treated samples. The reduction in $Cr^{3+}$ release for the untreated samples was more pronounced in the presence of montmorillonite, which was attributed to sorption. Treatment with quicklime, fly ash, or quick lime-fly ash was significantly effective in reducing $Cr^{3+}$ release most probably due to the formation of pozzolanic reaction products and $Cr(OH)_3$ precipitation. The most effective treatment was observed in montmorillonite-sand soil samples treated with quicklime-fly ash (99.8% removal). The mean $D_e$ decreased significantly and the mean LX was greater than 9 for all treated samples, indicating that the treated soils were acceptable for "controlled utilization". The mechanism controlling $Cr^{3+}$ leaching from all treated samples during the first 5 days appeared to be diffusion.

• Environmental Engineering Research
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• v.10 no.3
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• pp.112-121
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• 2005

The effectiveness of quicklime-based stabilization/solidification (S/S) in immobilizing lead (Pb) was assessed by performing semi-dynamic leaching tests (ANS16.1). In order to simulate landfill leaching conditions, the ANS 16.1 test was modified by using 0.014 N acetic acid (pH = 3.25) instead of distilled water. Artificial soil samples as well as field soil samples contaminated with Pb were tested. The effectiveness of quicklime treatment was evaluated by determining diffusion coefficients ($D_e$) and leachability indices (LX). A model developed by de Groot and van der Sloat was used to elucidate the controlling Pb leaching mechanisms. Overall, upon quicklime treatment Pb leachability was significantly reduced in a]l of the samples tested. The mean LX values were higher than 9 for an artificial soil sample containing 30% kaolinite treated with 10% quicklime and for a field soil sample treated with 10% quicklime, which suggests that S/S treated soils can be considered acceptable for "controlled utilization". Moreover, quicklime treatment was more effective in artificially contaminated soil with high kaolinite content (30%), indicating the amount of clay plays an important role in the success of the treatment. The controlling Pb leaching mechanism was found to be diffusion, in all quicklime treated samples.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.21-31
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• 2003

IAEA, FT-04-020, and ANS 16.1, standard leaching test methods, were evaluated comparatively with their test results. Leaching index of Co-60 and Cs-137 for all waste forms were above 6.0. Their leaching behavior were contrary according to the type of matrix and leachant. Leachability of Co in cement waste form was higher in simulated seawater than demi. water, and higher in demi. water in paraffin waste form. Leachability of Cs was contrary to Cs. Cumulative fraction leached of Co was higher such as IAEA＞ANS＞FT in cement waste form.

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2261-2267
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• 2021

This paper evaluates the efficacy of magnesium potassium phosphate cements (MKPCs) as waste forms for the solidification of radioactive concrete powder wastes produced by the decommissioning of nuclear power plants. MKPC specimens that contained up to 50 wt% of simulated concrete powder wastes (SCPWs) were evaluated. We measured the porosity and compressive strength of the MKPC specimens, observing them using scanning electron microscopy and X-ray diffraction. The addition of SCPWs reduced the porosity and increased the compressive strength of the MKPC specimens. Struvite-K crystals were well-synthesized, and no additional crystal phase was formed. After thermal cycling and after immersion, MKPC specimens with 50 wt% SCPWs satisfied the waste-acceptance criteria (WAC) for compressive strength. Semi-dynamic leaching tests were performed using the ANS 16.1 method; the leachability indices of Cs, Co, and Sr were 11.45, 17.63, and 15.66, respectively, which also satisfy the WAC. Thus, MKPCs can provide stable matrices to immobilize radioactive concrete wastes generated by the decommissioning of nuclear power plants.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.1 no.1
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• pp.93-103
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• 2003

IAEA, FT-04-020, and ANS 16.1, standard leaching test methods, were evaluated comparatively with their test results. Leaching index of $^{60}$ Co and $^{137}$ Cs by ANS 16.1 method for waste forms of paraffin and cement were above 6.0. Their leaching behavior were depending on the type of matrix and leachant. Leachability of $^{60}$ Co for cement waste form was higher in simulated seawater than do-mineralized water, and was higher in de-mineralized water for paraffin waste form. leachability of $^{60}$ Co was contrary to $^{137}$ Cs. Cumulative fraction leached of $^{60}$ Co was higher in order or IAEA ＞ ANS ＞ FT in a cement waste form.

• The Korean Journal of Pesticide Science
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• v.6 no.4
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• pp.309-319
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• 2002

Soil adsorption study was carried out to define the mobility of pesticides or to evaluate leaching potential in soils. Five pesticides including ethoprophos, procymidone, iprobenfos, isoprothiolane, and butachlor were subjected to optimized adsorption experiment protocol for three types of cultivation soils. Freundlich adsorption coefficients (K) were ranged $0.35{\sim}0.95$ for ethoprophos, $0.98{\sim}2.2$ for iprobenfos, $1.2{\sim}4.3$ for procymidone, $1.5{\sim}3.5$ for isoprothiolane and $7.9{\sim}19$ for butachlor in three soils. Based on Koc values, ethoprophos was classified as mobile, iprobenfos, isoprothiolane and procymidone as moderately mobile and butachlor as slightly mobile. Two evaluation methods, Groundwater Ubiquity Score (GUS) index and standard indices of soil-chemical adsorption and biodegradation, were used for the estimation of pesticide leaching potential. Leachability of isoprothiolane and iprobenfos were evaluated as moderate, ethoprophos as a little potential, while butachlor and procymidone showed very low leaching potential. The leaching potential of pesticides was essentially determined on the basis of intrinsic properties of the pesticides and environmental properties. Among the soil properties, organic matter gave a great influence on the leachability of soils. Therefore, leachabilities of pesticides were expected less in loam with relatively higher organic matter than clay loam with lower organic matter.

• Nuclear Engineering and Technology
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• v.55 no.10
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• pp.3617-3627
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• 2023

This study presents a method to solidify spent ion-exchange resin (IER) in a metakaolin-based geopolymer and shows results of mechanical strength, immersion, leaching, irradiation, and thermal cycling tests for waste acceptance criteria (WAC) to repository. The geopolymer waste form with 20 wt% of simulated spent IER met the WAC in South Korea (ROK), and the leaching tests of various sized-waste forms up to 15.0 × 30.0 cm and waste loadings up to 20 wt% for 1-5 d and 1-90 d achieved a leachability index, L_i > 6. In a leaching test for 5 d, the cumulative fraction leached (CFL) for Cs, which leached the most, was linearly correlated with the square root of leaching time for all waste forms, and L_i increased as the size of the waste form increased. The CFL was also correlated with elapsed time in the 90 d leaching test. The correlations among CFL, time, and volume-to-surface area ratio of waste forms used to estimate the L_i of Cs of a 200-L sized geopolymer with 15 wt% IER showed the L_i values as 14.73 (5 d) and 17.71 (90 d), respectively, indicating that the large-sized geopolymer waste form met the WAC.

• Korean Journal of Environmental Agriculture
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• v.24 no.4
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• pp.341-349
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• 2005

Soil adsorption study was carried out to define the mobility of pesticides and to evaluate leaching potential in soils. Nine pesticides including metolcarb, molinate, fenobucarb, isazofos, diazinon, fenitrothion, dimepiperate, parathion and chlorpyrifos-methyl were subjected to adsorption experiment for four types of soils, such as upland, paddy, forest and volcanic ash soil. Based on Koc values, metolcarb and molinate were classified as mobile, fenobucarb as mobile or moderately mobile isazofos as moderately mobile, diazinon, fenitrothin, dimepiperate, and parathion as slightly or moderately mobile and chlorpyrifos-methyl as slightly mobile. Two evaluation methods, Groundwater Ubiquity Score (GUS) index and standard indices of soil-chemical adsorption and biodegradation (half-life), were used for the estimation of pesticide leaching potential. Leachabilities of metolcarb, molinate and fenobucarb were evaluated as high, and isazofos, dimepiperate and diazinon as a little potential, while fenitrothion, parthion and chlorpyrifos-methyl showed very low leaching potential. The leaching potential of pesticides was determined on the basis of intrinsic properties of the pesticides and the soil properties. Among the soil properties, organic matter gave a great influence on the leachability in soil. Therefore, leachabilities of the pesticides used were expected less in Sineom soil with relatively higher organic matter than Gangseo, Jungdong and Yesan soil with lower organic matter.