• Title, Summary, Keyword: leaching

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Studies on the Leaching Test in Industrial Waste (폐기물 용출시험법에 관한 연구)

  • 어수미
    • Journal of Environmental Health Sciences
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    • v.20 no.4
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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.

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Quantitative Evaluation of Leaching Model System for Soil Fungistasis (Leaching Model System에 의한 토양(土壤) 정균현상(靜菌現象)의 분석(分析))

  • Heo, Hyun;Hong, In-Pyo;Lee, Min-Woong
    • The Korean Journal of Mycology
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    • v.15 no.4
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    • pp.254-259
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    • 1987
  • This study was carried out to investigate the germination of four fungi under non-leaching and leaching incubation. The range of germination rates of Fusarium solani f. sp. pisi, Fusarium oxysporum f. sp. cucumerium, Mortierella, and Helminthosporium sativa incubated on sand saturated with various solutions without leaching were 90-99%, 31-45%, 38-62% and 86-98% respectively. The range of germination rates of Fusarium solani f. sp. pisi, Fusarium oxysporum f. sp. cucumerium, Mortierella n. sp and Helminthosporum sativa incubated on sand undergoing leaching were 51-63%, 13-25%, 15-37% and 47-80%, respectively. The germination rates of the four fungi tested were suppressed under leaching incubation.

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Leaching Characteristics of Heavy Metals of Bottom Ash and Plating Sludge with Environmental Conditions in Landfill (매립지 환경조건을 고려한 소각재와 도금슬러지의 중금속 용출특성)

  • 손희정;김은호;이용희
    • Journal of environmental and Sanitary engineering
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    • v.13 no.2
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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.

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A Study on The Comparison of Leaching Methods and Stability of Cement Mortar Solidified Cadmium sludge (시멘트고화에 의한 카드뮴슬러지의 안정성 및 용출실험방법 비교 검토)

  • 주소영;김광렬
    • Journal of environmental and Sanitary engineering
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    • v.17 no.3
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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.

Ultrasonic-assisted leaching kinetics in aqueous FeCl3-HCl solution for the recovery of copper by hydrometallurgy from poorly soluble chalcopyrite

  • Yoon, Ho-Sung;Kim, Chul-Joo;Chung, Kyung Woo;Lee, Jin-Young;Shin, Shun Myung;Kim, Sung-Rae;Jang, Min-Ho;Kim, Jin-Ho;Lee, Se-Il;Yoo, Seung-Joon
    • The Korean Journal of Chemical Engineering
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    • v.34 no.6
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    • pp.1748-1755
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    • 2017
  • We studied the ultrasonic effect on the leaching of copper from poorly soluble chalcopyrite ($CuFeS_2$) mineral in aqueous $FeCl_3$ solution. The leaching experiment employed two methods, basic leaching and ultrasonic-assisted leaching, and was conducted under the optimized experimental conditions: a slurry density of 20 g/L in 0.1 M $FeCl_3$ reactant in a solution of 0.1 M HCl, with an agitation speed of 500 rpm and in the temperature range of 50 to $99^{\circ}C$. The maximum yield obtained from the optimized basic leaching was 77%, and ultrasonic-assisted leaching increased the maximum copper recovery to 87% under the same conditions of basic leaching. In terms of the leaching mechanism, the overall reaction rate of basic leaching is determined by the diffusion of both the product and ash layers based on a shrinking core model with a constant spherical particle; however, in the case of ultrasonic-assisted leaching, the leaching rate is determined by diffusion of the ash layer only by the removal of sulfur adsorbed on the surface of chalcopyrite mineral.

A Comparative Study for Leaching Characteristics of Specified By-Products due to Changes in Acid Neutralization Capacities (지정부산물의 산중화능력변화에 따른 용출특성 비교연구)

  • 이현경;박주양
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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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.

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Nutrient Leaching from Leaf Litter of Emergent Macrophyte(Zizania latifolia) and the Effects of Water Temperature on the Leaching Process

  • Park, Sangkyu;Cho, Kang-Hyun
    • Animal cells and systems
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    • v.7 no.4
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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.

Recovery of Tungsten from WC/Co Hardmetal Sludge by Alkaline Leaching Hydrometallurgy Process (WC/Co 초경합금 가공 슬러지로부터 알칼리침출 정련공정에 의한 W 회수)

  • Lee, Gil-Geun;Kwon, Ji-Eun
    • Journal of Korean Powder Metallurgy Institute
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    • v.23 no.5
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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.

Ammonium Chloride Solution Leaching of Crude Zinc Oxide Recovered from Reduction of EAF′s Dust

  • Youn, Ki-Byoung
    • Proceedings of the IEEK Conference
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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.

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Reusing the Liquid Fraction Generated from Leaching and Wet Torrefaction of Empty Fruit Bunch

  • Lee, Jae-Won;Choi, Jun-Ho;Im, Hyeon-Soo;Um, Min;Lee, Hyoung-Woo
    • Korean Chemical Engineering Research
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    • v.57 no.3
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    • pp.372-377
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    • 2019
  • Leaching ($60^{\circ}C$, 5 min) and wet torrefaction ($200^{\circ}C$, 5 min) of empty fruit bunch (EFB) were carried out to improve the fuel properties; each liquid fraction was reused for leaching and wet torrefaction, respectively. In the leaching process, potassium was effectively removed because the leaching solution contained 707.5 ppm potassium. Inorganic compounds were accumulated in the leaching solution by increasing the reuse cycle of leaching solution. The major component of the leached biomass did not differ significantly from the raw material (p-value < 0.05). Inorganic compounds in the biomass were more effectively removed by sequential leaching and wet torrefaction (61.1%) than by only the leaching process (50.1%) at the beginning of the liquid fraction reuse. In the sequential leaching and wet torrefaction, the main hydrolysate component was xylose (2.36~4.17 g/L). This implied that hemicellulose was degraded during wet torrefaction. As in the leaching process, potassium was effectively removed and the concentration was accumulated by increasing the reuse cycle of wet torrefaction hydrolysates. There was no significant change in the chemical composition of wet torrefied biomass, which implied that fuel properties of biomass were constantly maintained by the reuse (four times) of the liquid fraction generated from leaching and wet torrefaction.