• Journal of the Korean Wood Science and Technology
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• 제44권3호
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• pp.360-369
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• 2016

본 연구에서는 팜 부산물인 Empty Fruit Bunch (EFB)의 연료적 특성을 향상시키기 위해 용탈처리와 습식 반탄화를 연속적으로 수행하였다. 용탈처리는 $25{\sim}90^{\circ}C$에서 5~30분 수행하였으며, $90^{\circ}C$, 10분 조건에서 55.99%의 가장 높은 회분 감소율을 나타냈다. 회분 감소율은 용탈 시간보다 온도에 따라 영향을 받았다. 용탈처리 후 연속적으로 습식 반탄화를 수행하였으며 반응온도 $180{\sim}200^{\circ}C$, 반응시간 5~40분에서 실시하였다. 연속처리에 의해 규소를 제외한 대부분의 무기성분은 제거되었으며 회분 감소율은 41.05~63.58%로 나타났다. 특히, 염소, 칼륨, 마그네슘, 인 성분은 80%이상 제거되었다. 용탈처리 후 $200^{\circ}C$, 40분에서 습식 반탄화를 수행한 결과 발열량은 원시료(4390 kcal/kg)와 비교하여 7.96% 증가한 4736 kcal/kg를 나타냈다.

• 한국농공학회지
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• 제40권4호
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• pp.77-84
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• 1998

Adsorption and leaching characteristics of the artificial soils produced from water and wastewater treatment sludges were examined. The batch adsorption test and TCLP leaching test were used, and constituents of interest were heavy metals and nutrients. As, Cr, Cu, Pb, and Cd were analyzed for metals, and nitrogen and phosphorus were analyzed for nutrients. All the artificial soils showed strong adsorption and low leaching for the heavy metals, which implies that the artificial soils may not be hazardous to the environment due to heavy metals and even they can be utilized effectively to remove metals in solution like mine and industrial wastewaters. This is quite promising result because in most case heavy metals are the most concern in the application of sludge product to the farmland. For the nutrients, generally, artificial soils showed high adsorption and low leaching except artificial soil from wastewater sludge produced by low temperature firing. The artificial soils produced from water treatment sludge were active in adsorbing nutrients and showed low leaching that they can be practically used to remove nutrients in advanced treatment process of the wastewater. The artificial soils produced from wastewater treatment sludge were less active in adsorbing nutrients and showed high teaching. However, they could be used usefully if applied properly to the plant growing because of their fertilizing effect. Based on the test results, overall, the artificial soils were thought to be not hazardous to the environment and they could be more useful if applied properly.

• Nuclear Engineering and Technology
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• 제32권1호
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• pp.10-16
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• 2000

Preliminary experiment was peformed to investigate the leaching characteristics of paraffin waste forms that had been recently generated in large quantities at domestic nuclear power plants. At first, waste simulants whose compositions were different in mixing ratio of paraffin to boric acid were prepared. Their compressive strengths were measured and ninety-day leaching test of specimen including cobalt was carried out according to ANSI/ANS-16.1 test procedure. Water immersion test was also conducted keeping pace with leaching test and the weight change and the compressive strength of specimen were observed after ninety days. The compressive strength of waste form exhibited 666 psi (4.53 MPa) in the case where mixing ratio of boric acid to paraffin was 78/22, which was adopted in concentrate waste drying system of domestic nuclear power plants. The leaching test resulted in about 50% of the cumulative fraction leached for boric acid and cobalt, respectively. The specific gravity of waste form was 0.87 ［g/g］whose value was less than that of water because the weight loss of about 39% occurred after the water immersion test of ninety days. It was also observed that the waste form which had undergone ninety-day water immersion test exhibited the compressive strength of 203 psi (1.38 MPa).

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.2889-2896
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• 2023

The waste acceptance criteria for heavy metals in mixed waste should be developed by reflecting the leaching behaviors that could highly depend on the repository design and environment surrounding the waste. The current standards widely used to evaluate the leaching characteristics of heavy metals would not be appropriate for the silo-type repository since they are developed for landfills, which are more common than a silo-type repository. This research aimed to explore the leaching behaviors of cementitious waste with Pb, Cd, and Sb metallic and oxide powders in an environment simulating a silo-type radioactive waste repository. The Toxicity Characteristic Leaching Procedure (TCLP) and the ANS 16.1 standard were employed with standard and two modified solutions: concrete-saturated deionized and underground water. The compositions and elemental distribution of leachates and specimens were analyzed using an inductively coupled plasma optical emission spectrometer (ICP-OES) and energy-dispersive X-ray spectroscopy combined with scanning electron microscopy (SEM-EDS). Lead and antimony demonstrated high leaching levels in the modified leaching solutions, while cadmium exhibited minimal leaching behavior and remained mainly within the cement matrix. The results emphasize the significance of understanding heavy metals' leaching behavior in the repository's geochemical environment, which could accelerate or mitigate the reaction.

• Geomechanics and Engineering
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• 제18권6호
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• pp.585-594
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• 2019

In-situ leaching could be one of the promising mining methods to extract the minerals from deep fractured rock mass. Constrained by the low permeability at depth, however, the performance does not meet the expectation. In fact, the rock mass permeability mainly depends on the pre-existing natural fractures and therefore play a crucial role in in-situ leaching performance. More importantly, fractures have various characteristics, such as aperture, persistence, and density, which have diverse contributions to the promising method. Hence, it is necessary to study the variation of fluid rate versus fracture parameters to enhance in-situ leaching performance. Firstly, the subsurface fractures from the depth of 1500m to 2500m were mapped using the discrete fracture network (DFN) in this paper, and then the numerical model was calibrated at a particular case. On this basis, the fluid flow through fractured rock mass with various fracture characteristics was analyzed. The simulation results showed that with the increase of Fisher' K value, which determine the fracture orientation, the flow rate firstly decreased and then increased. Subsequently, as another critical factor affecting the fluid flow in natural fractures, the fracture transmissivity has a direct relationship with the flow rate. Sensitive study shows that natural fracture characteristics play a critical role in in-situ leaching performance.

• Journal of the Korean Wood Science and Technology
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• 제34권5호
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• pp.98-103
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• 2006

Radial and tangential diffusion coefficients of boron in wood under water leaching conditions were determined from the change of concentration profiles of boron. Egner's solution was used to obtain variable diffusion coefficients of boron because it has been known to be the only method to determine variable diffusion coefficients with no cumbersome assumption. The values of diffusion coefficients were between $0.18{\times}10^{-6}m^2/sec$ and $25.6{\times}10^{-6}cm^2/sec$. They increased with the increase of sample thicknesses, and decreased with the increase of leaching times. There was a region where Egner's method was not valid. However, Egner's solution illustrates a convenient way to evaluate diffusion characteristics of boron from wood under water leaching conditions. The diffusion coefficients at wood surface may be regarded as leaching coefficients.

• 한국지하수토양환경학회지:지하수토양환경
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• 제6권1호
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• pp.23-31
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• 2001

용융처리는 중금속을 안정화시키는 효과적인 방법의 하나이며, 또한 고가의 부산물을 생산해낸다. 본 연구에서는 소각재를 용융하여 얻은 슬래그의 중금속 용출특성을 평가하고자 한다. 슬래그를 재활용하는데 있어서 환경적인 적합성을 평가하기 위하여 소각재, 슬래그 및 슬래그를 재활용재로 하여 제조한 건설재료에 대한 용출시험을 수행하였다. 시험결과는 다음과 같다. (1) 국내표준용출시험법(KSLT)에 의해 시험한 슬래그의 중금속 용출농도는 소각재의 용출농도보다 낮은 값을 나타냈다. (2) 장기용출시험법에 의해 평가한 슬래그의 중금속 용출농도도 KSLT의 기준을 만족했다. (3) 슬래그의 건설재료로서의 사용성을 평가하기 위해 만든 모르타르 공시체의 용출결과, 슬래그를 재활용재로서 사용하는데 있어서 중금속 용출 측면에서 적합하다고 사료된다. (4) 독일의 소각재 재활용을 위한 가이드라인인 RG Min-StB 93, FGSV에서 제시하는 방법에 의해 시험한 결과, 본 슬래그의 용출농도는 독일의 규제기준을 만족하였다.

• 농업과학연구
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• 제49권2호
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• pp.379-387
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• 2022

A large amount of the mineral nitrogen is necessary for crop growth. With the use of nitrogen fertilizers, agricultural yield has increased during the last few decades. However, at the same time, nitrate from the cultivated land can be a source of environmental pollution, especially in water systems. For nitrogen management, it is necessary to analyze the pattern of nitrogen movement in soil. In this study, nitrogen leaching in upland soils was evaluated using undisturbed lysimeters with different soil textures during sesame cultivation. The soil texture of the lysimeters was clay loam (Songjung series) and sandy loam (Sangju series) soils. Sesame was cultivated from May 25 to August 24 in 2020. The standard amount of NPK fertilizer (N-P₂O₅-K₂O = 2.9-3.1-3.2 kg·10 a^-1) was applied before sowing. The amount of nitrogen leaching was calculated by multiplying the nitrogen (NO₃-N + NH₄-N) concentration and the amount of water drained below 1.5 m soil depth. The water was drained through percolation into macropores in the clay loam lysimeter. In contrast, in the sandy loam lysimeter, water drained more slowly than in the clay loam lysimeter. There was a slight difference in the total amount of leachate during the cultivation period, but the amount of nitrogen leaching was high in sandy loam soil. During the sesame cultivation period, the amount of nitrogen leaching from clay soil was 5.64 kg·10 a^-1, and 10.70 kg·10 a^-1 for sandy soil. We found that there was a difference in leaching depending on the soil physical characteristics. Therefore, it is necessary to consider the characteristics of soil to evaluate the leaching of nitrogen.

• 환경위생공학
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• 제14권3호
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• pp.22-30
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• 1999

This study was carried out to examine the compressive strength characteristics of solids solidified with the lead sludge with mixture of cement and fly ashes as additive. And the additives are commercial fly ash and ESP(Electrostatic precipitator) fly ash. The compressive strength of solidified lead sludge solid was increased by adding fly ash up to 46~62%, which was the results of pozzolanic reaction. When replaced the cement with 10%of commercial fly ash, the solid showed the highest value $210{\;}kg/cm^2$, and the solidification conditions were 0.55 of the water/cement ratio and curing for 14 days. Also, the results of leaching test by EPT(Environmental Protection Agency-Toxicity Test) were showed that the solidified lead has leached out under 10%, which was less than 0.173 mg/L of EPA standard. As leaching solutions, the demineralized water, 0.1N acetic acid solution, and synthetic brine were used. and the observations by SEM of the solidified lead-laden solid after EPT leaching test were indicated the severe erosion on solid surface.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.920-925
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• 2008

In this presentation, a leaching experiment which is followed the pH changes(pH=4, pH=7) and the mixing rates(1%, 3%, 5%, 7%) was carried out to examine the arsenic reduction effects and the leaching characteristics on arsenic contaminated soil after stabilization treatment in which 5 materials were used as stabilization agencies, i.e. ZVI(zero valent iron), blast furnace slag, steel refining slag, quick lime, and oyster shell meal. Except for blast furnace slag, the arsenic removal rate increased as the mixing rate increases of stabilization agencies. Arsenic leaching concentration was indicated that pH=7 condition is higher than pH=4 condition. This result shows because arsenic immobilization reaction increases as pH decreases, and arsenic adsorption takes place as pH decreases.