• 한국환경보건학회지
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• 제20권4호
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• pp.72-79
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• 1994

This study was performed to improve many problems of leaching test of industrial waste sludge analysis. We analyze sludges by variation of leachant, pH and leaching time.The results were as follows: 1. As leaching at pH 5.8 by our leaching test without control of pH during leaching, the leaching rates were very low as below 1%. 2. As leaching at pH 5.8 continuously by hydrochloric acid every 2 hour, the leaching rates were higher than before 1. 3. As leaching at pH 5.0 continuously by acetic acid every 2 hour, the leaching rates were higher than 1, 2. 4. The variations of leaching rate by leaching time were smaller increase after 10 hours than before. 5. It will be recommendable that the pH of leachant maintain constantly during leaching as level of acid rain, and the acetic acid is more effective than hydrochloric acid as leachant.

• 한국균학회지
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• 제15권4호
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• pp.254-259
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• 1987

4가지 균주의 포자를 4가지의 용액으로 Non-leaching과 Leaching하에서 배양하고 발아율을 조사한 결과 다음과 같다. Non-leaching배양된 Fusarium solani f. sp. pisi의 경우 포자발아율은 pfeffer's solution에서 90%로 가장 낮았으며 Buffer solution에서 99%로 가장 높았다. Leaching배양의 경우 subsoil extract에서 51%로 포자발아가 억제되었고 pfeffer's solution에서 63%로 덜 억제되었다. Non-leaching배양한 Fusarium oxysporum f. sp. cucumerium의 경우 포자발아율은 증류수에서 31%로 가장 적게 억제되었고 Buffer solution에서 45%로 가장 많이 억제되었다. Leaching배양의 경우 Buffer solution에서 17.5%로 가장 억제되었고 증류수에서 25%로 덜 억제되었다. Non-leaching배양한 Helminthosporium sativa의 경우 증류수에서 86.1%로 발아가 낮았고 Buffer solution에서 98%로 높았다. Leaching배양의 경우 Buffer solution에서 47%로 발아가 억제되었고 증류수에서 80.4%로 덜 억제되었다. Non-leaching배양한 Mortierella n. sp.의 경우 발아율은 subsoil extract에서 38.5%로 낮았고 증류수에서 62.5%로 높았다. Leaching배양의 경우 발아율은 증류수에서 15%로 크게 억제되었고 pfeffer's solution에서 37.5%로 덜 억제되었다.

• 환경위생공학
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• 제13권2호
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• pp.121-127
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• 1998

This study was to understand leaching characteristics with pH controlling agents and Temp. control, and investigate leaching characteristics with pH control from opening a leaching test to an end for reassessing leaching test of heavy metals with environmental conditions in landfill. Because leaching of heavy metals was increased in low pH, pH must control for leaching in existing leaching test. Generally, regulation time(6hr) of leaching was confirmed reasonablely, except for Cu in plating sludge. In pH controlling solution, there was nearly not difference between Acetic acid and HCl and if considering Cu, the former was appropriate. In a part of heavy metal, leaching rate was increased in high Temp., and normal Temp. in existing leaching test would be revaluated.

• 환경위생공학
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• 제17권3호
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• pp.21-30
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• 2002

This study was Performed to evaluate the effective solidification of Cd sludge using cement and power plant fly ash as cement admixture, to identify the leaching characteristics of the heavy metal Cd sludge solidified, and to develope proper KLT(Korean Leaching Test) of hazardous waste. KLT was compared with EPT(Extraction Procedure Toxicity) and TCLP(Toxicity Characteristics Leaching Procedure). Fly ash contents ranged from 0% to 30% of cement weight. The experimental results showed that the optimum amount of fly ash replaced was 10% to 15% and KLT was less appropriate than EPA and TCLP. Also the purpose of the study was to suggest the modification factors on the leaching test currently used, based on the above mentioned aspects. The effects of pH, leaching time, leaching for agitating intensity, and leaching solvent were investigated. As the result of test, the leaching potential was relatively high when the pH and agitation intensity of leaching solution were 5 and 150rpm, respectively. Leaching time of six hours was found to be sufficient and the use of acetic acid as a leaching solvent is more useful in landfill site particularly.

• Animal cells and systems
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• 제7권4호
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• pp.289-294
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• 2003

To quantify nutrient loading from emergent macrophytes through leaching in the littoral zones of Paldang Reservoir, we conducted incubation experiments using leaf litter of the emergent macrophyte, Zizaniz latifolia. To separate the leaching process from microbial decay, we used $HgCl_2$ to suppress microbial activity during the experiment. We measured electric conductivity, absorbance at 280nm, total nitrogen and dissolved inorganic nitrogen, total phosphorus and soluble reactive phosphorus, Na, K, Mg and Ca amounts in leaf litter and in water. In addition, we examined the effects of water temperature and ion concentrations of ambient water on the leaching process. A total of 6% of the initial ash-free dry mass of leaf litter was lost due to leaching during incubation (four days). Electric conductivity and A280 continued to increase and saturate during the incubation. To compare reaching rates of different nutrients, we fitted leaching dynamics with a hyperbolic saturation function [Y=AㆍX/(B+X)]. From these fittings, we found that ratios of leaching amounts to nutrient concentration in the litter were in the order of K > Na > Mg > P > Ca > N. Leaching from leaf litter of Z. latifolia was dependent on water temperature while it was not related with ion concentrations in the ambient water. Our results suggest that the leaching process of nutrients, especially phosphorus, from aquatic macrophytes provides considerable contribution to the eutrophication of the Paldang Reservoir ecosystem.

• 한국분말재료학회지
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• 제23권5호
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• pp.372-378
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• 2016

This study focuses on the development of an alkaline leaching hydrometallurgy process for the recovery of tungsten from WC/Co hardmetal sludge, and an examination of the effect of the process parameters on tungsten recovery. The alkaline leaching hydrometallurgy process has four stages, i.e., oxidation of the sludge, leaching of tungsten by NaOH, refinement of the leaching solution, and precipitation of tungsten. The WC/Co hardmetal sludge oxide consists of $WO_3$ and $CoWO_4$. The leaching of tungsten is most affected by the leaching temperature, followed by the NaOH concentration and the leaching time. About 99% of tungsten in the WC/Co hardmetal sludge is leached at temperatures above $90^{\circ}C$ and a NaOH concentration above 15%. For refinement of the leaching solution, pH control of the solution using HCl is more effective than the addition of $Na_2S{\cdot}9H_2O$. The tungsten is precipitated as high-purity $H_2WO_4{\cdot}H_2O$ by pH control using HCl. With decreasing pH of the solution, the tungsten recovery rate increases and then decrease. About 93% of tungsten in the WC/Co hardmetal sludge is recovered by the alkaline leaching hydrometallurgy process.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 총회 및 춘계학술발표회
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• pp.206-209
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• 2001

This study presents the leaching characterization of heavy metals according to changes of pH by ANC test on slag produced in electric arc furnace, bottom ash produced in coal-fired plants and their recycling products. Availability test was performed to assess the fraction of the total concentration that under worst environmental conditions could become available for leaching. TCLP, KLT(Korea Leaching Test) and KLTS(Korea Leaching Test of Soil contamination) were carried out to compare the leaching capacity and to estimate the adequacy of regulatory leaching test. Results from regulatory leaching tests could be misleading because the variable ANC of wastes can lead to very different final leachate pHs. The final pH of the regulatory test is not the ambient pH in the disposal environment, the actual solubilities of contaminants in the field may be entirely different from those predicted by these regulatory tests. Leaching behaviour of by-products was changed by recycling processes, therefore acid neutralization capacity and availability of new products, not leaching concentration by one batch regulatory test, are necessary to determine the method of recycling.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.365-369
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• 2001

EAF's dust has been treated mainly by pyrometallurgical reduction process in rotary kiln furnace to recover valuable metal elements such as Zn and to avoid the disposal of hazardous materials to waste. Recently, hydrometallurgical eletrowinning of zinc from a zinc-amino chloride solution obtained by the leaching of EAF's dust was developed to recover high grade zinc metal from EAF’s dust. But there are some disadvantages in each process such as difficulty of operation condition control and sticking problem in kiln process and low extractability and recovery of zinc owing to insoluble zinc-ferrite in electrowinning process. We propose a new combined process of pyrometallurgical one and hydrometallurgical one to treat EAF's dust efficiently and economically. In this study, ammonium chloride solution leaching of crude zinc oxide recovered from reduction of EAF's dust was carried out to find out the efficiency of zinc extraction from it and the possibility for performance of eletrowinning in the proposed process. Effects of various leaching variables ruck as leaching temperature, concentration of leaching solution and leaching time were investigated. And the leaching results of the crude zinc oxide were compared with those of EAF's dust. The extraction percents of zinc in ammonium chloride solution leaching of the crude zinc oxide recovered from reduction of EAF's dust were above 80% after 60 minutes of leaching under the leaching condition of 4M NH$_4$CI concentration and above leaching temperature of 7$0^{\circ}C$. And the concentrations of zinc in the leached solution were obtained above 50g/$\ell$. The activation energy calculated for zinc extraction in NH$_4$CI leaching was 58.1 KJ/㏖ for EAF's dust and 15.8 KJ/㏖ for the crude zinc oxide recovered from reduction of EAF's dust.

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.566-574
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• 2023

Investigating the seepage characteristics of the leaching solution in the ore-bearing layer during the in situ leaching process can be useful for designing the process parameters for the uranium mining well. We prepared leaching solutions of four different viscosities and conducted experiments using a self-developed multifunctional uranium ore seepage test device. The effects of different viscosities of leaching solutions on the seepage characteristics of uranium-bearing sandstones were examined using seepage mechanics, physicochemical seepage theory, and dissolution erosion mechanism. Results indicated that while the seepage characteristics of various viscosities of leaching solutions were the same in rock samples with similar internal pore architectures, there were regular differences between the saturated and the unsaturated stages. In addition, the time required for the specimen to reach saturation varied with the viscosity of the leaching solution. The higher the viscosity of the solution, the slower the seepage flow from the unsaturated stage to the saturated stage. Furthermore, during the saturation stage, the seepage pressure of a leaching solution with a high viscosity was greater than that of a leaching solution with a low viscosity. However, the permeability coefficient of the high viscosity leaching solution was less than that of a low viscosity leaching solution.

• 광물과 암석
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• 제33권3호
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• pp.243-250
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• 2020

본 연구의 목적은 선상에서 열수광물 내 Au를 효과적으로 용출하기 위한 마이크로웨이브-차아염소산 용출의 적용 가능성을 파악하는 것이다. 비교용출실험은 마이크로웨이브 질산용출의 유(T1)/무(T2)에 따른 Au 용출율의 영향을 확인하였다. 또한, 기계적 교반에 의한 전통적인 용출(T3)과 마이크로웨이브 용출에 따른 Au 용출율을 비교하였다. 마이크로웨이브 질산용출결과(고액비; 10%, 용출온도; 90℃, 용출시간; 20분), 금속의 용출율은 As>Pb>Cu>Fe>Zn 순으로 높게 나타났으며, 용출잔사 내 Au의 함량은 33.77 g/ton에서 60.02 g/ton으로 증가하였다. 염화물 용매제를 이용한 비교용출실험 결과, Au의 용출율은 T1(61.10%)>T3(53.30%)>T2(17.30%)순으로 높게 나타났다. 따라서, 해수를 이용하여 제조 가능하고 용출과정에서 발생되는 염소 가스를 포집하여 재이용 가능한 염화물은 Au용출을 위한 최적의 용매제로 예상된다. 또한 마이크로웨이브를 적용함으로써 시간, 효율 및 에너지 측면에서 효과적일 것으로 판단되어진다.