• Mineral and Industry
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• v.26
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• pp.1-12
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• 2013

In this study, an accelerated carbonation process was applied to stabilize hazardous heavy metals of industrial solid waste incineration (ISWI) bottom ash and fly ash, and to reduce $CO_2$ emissions. The most commonly used method to stabilize heavy metals is accelerated carbonation using a high water-to-solid ratio including oxidation and carbonation reactions as well as neutralization of the pH, dissolution, and precipitation and sorption. This process has been recognized as having a significant effect on the leaching of heavy metals in alkaline materials such as ISWI ash. The accelerated carbonation process with $CO_2$ absorption was investigated to confirm the leaching behavior of heavy metals contained in ISWI ash including fly and bottom ash. Only the temperature of the chamber at atmospheric pressure was varied and the $CO_2$ concentration was kept constant at 99% while the water-to-solid ratio (L/S) was set at 0.3 and $3.0dm^3/kg$. In the result, the concentration of leached heavy metals and pH value decreased with increasing carbonation reaction time whereas the bottom ash showed no effect. The mechanism of heavy metal-stabilization is supported by two findings during the carbonation reaction. First, the carbonation reaction is sufficient to decrease the pH and to form an insoluble heavy metal-material that contributes to a reduction of the leaching. Second, the adsorbent compound in the bottom ash controls the leaching of heavy metals; the calcite formed by the carbonation reaction has high affinity of heavy metals. In addition, approximately 5 kg/ton and 27 kg/ton $CO_2$ were sequestrated in ISWI bottom ash and fly ash after the carbonation reaction, respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.56-64
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• 2019

Various approaches have been attempted to develop recycling technologies related to industrial waste resources containing metals. Among them, glass is not decomposed into microorganisms, so landfill is not suitable, and interest in the recycling of waste glass is increasing. In this paper, by incorporating chelate resin to suppress the elution of heavy metals in waste glass and using waste glass as a fine aggregate and we want to evaluate the strength, drying shrinkage, alkali-silica reaction and heavy metal leaching of shielded filler materials and to provide basic data for utilizing waste glass as an economical and environmentally friendly shielding filler. As a result of the test, it was found that the use of waste glass as a fine aggregate was effective in the development of strength, but the incorporation of chelate resin had an influence on the strength development. In addition, the addition of chelate resin was effective in improving drying shrinkage but it was found to affect the alkali - silica reaction. As a result of the heavy metal leaching test, the KSLP test method satisfies all the criteria for heavy metal leaching. However, in case of lead, the limit of US ANSI 67-2007a was exceeded and further study should be done.

• Journal of the Korean Applied Science and Technology
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• v.35 no.3
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• pp.876-885
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• 2018

Utilization of spent RHDM(Residue Hydrodemetallation) catalyst as de-NOx SCR(Selective Catalytic Reduction) catalyst was studied by conducting by heptane cleaning and high-temperature roasting for removal of deposited carbon and sulfur. Followed by oxalic acid leaching was carried out for controlling excess vanadium deposited on spent RHDM catalyst in search of appropriate vanadium loadings for the best SCR performance and the leaching conditions are 5~15wt% concentration of oxalic acid and 5min leaching time at $50^{\circ}C$ with the ultra-sonic agitator. De-NOx activities of prepared and commercial SCR catalyst were measured by the atmospheric SCR catalyst performance test unit, their residual content were also carried out by ICP, C&S Analysis and XRF. Acid leaching (AL-10) catalyst showed the highest de-NOx efficiency of all prepared catalysts and the de-NOx efficiency over wash coated catalyst(WC-AL-10) was equivalent to that of commercial SCR catalyst. Therefore the possibility of using as SCR catalyst for each application by adjusting treatment conditions of spent RHDM catalyst was found and further research will be needed in detail for the its commercialization.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.1
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• pp.1-7
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• 2013

This study was on leaching test(KSLT, TCLP) of the aggregate for the products(RA-1) and for the site(RA-2) to evaluate the characteristics of contaminants and the possibility of contamination arising from the aggregate. On the basis pH, conductivity and heavy metal contents in the aggregate, RA-1 indicated higher than RA-2. As a result of the leaching test, the pollutants were eluted from the aggregate increased as the particle size of the aggregate was smaller. The pH in the aggregate had a strong alkali by a pH value of 9.0~12.3, the conductivity was higher in less than 10mm RA-1 due to the leaching of dissolved inorganic ions. The heavy metals satisfied the leaching standards of KSLT and less 10% was eluted from the aggregate. As a result of evaluating water pollution possibility of the aggregate, the pH displayed in items with a very high possibility of contamination, conductivity and turbidity did in item with a low possibility of contamination and on the other hand the heavy metals did in item with a very low possibility of contamination.

• Journal of Soil and Groundwater Environment
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• v.10 no.3
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• pp.1-8
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• 2005

Fractional compositions and leaching potentials of Cd, Cu and Zn were investigated in the soils which had been disposed with the metal processing wastes, tungsten mine tailings and low quality coal mine area. Total concentrations of metals in these soils were higher than in non-polluted paddy and upland soils. Fractions of Cd, Cu and Zn were mostly reducible, organic and residual forms, but varied with origins of wastes. Residual fraction was a predominant form in the nonpolluted soils. Leaching potentials of metals were higher in polluted soils than in non-polluted soils. Metals leached were higher at pH 4.0 than 7.0 and increased with the duration time. After 25 to 35 hrs, metals released from soils reached a pseudoequilibrium. Leaching potential of metals in non-polluted soils was low due to high percentage of residual fractions.

• Resources Recycling
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• v.26 no.6
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• pp.91-96
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• 2017

Tungsten (W) recovery from tungsten carbide (WC) was researched by alkali melt followed by water leaching. The experiments of alkali melt were carried out with the change of the sort of alkali material, heating temperature, and the heating duration. Water leaching of W was performed in the fixed conditions ($25^{\circ}C$, 2 hr., slurry density: 10 g/L). From the mixture of WC and sodium nitrate ($NaNO_3$) in the molar ratio of 1:2, treated at $400^{\circ}C$ for 6 hours, only 63.3% of W might be leached by water leaching. With the increase of sodium hydroxide (NaOH) as a melting additive, the leachability increased. Finally it reached to 97.8 % with the melted mixture of ($WC:NaNO_3:NaOH$) in the ratio of (1:2:2). This imply that NaOH may play a role as a reaction catalyst by lowering Gibb's free energy for alkali melt reaction for WC.

• Resources Recycling
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• v.22 no.6
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• pp.55-63
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• 2013

In this study, a electrochemical-chemical combined dissolution technology was conducted by electro-generated chlorine to obtain ruthenium solution from ruthenium metal. To find out the optimum leaching conditions of ruthenium in chloride solution, this leaching process was carried out on the variation of pH, reaction time, temperature and applied voltage at the electro-generated chlorine system in the reaction bath. Also, ozone generator was used to obtain ruthenium(III) chloride solution to increase the leaching rate. The optimum condition was observed at pH 10.0, $40^{\circ}C$ within 1 hr of reaction time that more than 88% of ruthenium(III) chloride dissolved.

• Resources Recycling
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• v.3 no.2
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• pp.17-23
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• 1994

The dissolution of gold and silver from concentrate was studied with acidic thiourea solution. The results showed that the gold and silver extraction was severely affected by concentration of thiourea and oxidant, pulp density, etc. Especially, oxidant such as ferric ions enhanced the leching rate of gold and silver. High concentration of ferric ions, however, dissolved the sulfide ore to form electrochemically passive layer on the surface of ore particles, which caused the precious metal not to be leached out from the ore. The use of $SO_2$could not effectively enhance the recovery of precious metal but reduce to some extent the consumption of thiourea. The leaching of gold and silver was achieved with recovery more than 90% and 80%, respectively, under the following conditions; Thiourea conc. :0.4M Oxidant : None $H_2SO_4$ conc. : 0.5M Pulp density : <10% Leaching time :4 Hrs Potential :250mV The Thiourea was consumed about 10% in comparison with its initial concentration.

• Journal of the Korean GEO-environmental Society
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• v.3 no.4
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• pp.37-49
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• 2002

In this study, it is performed that mix design of grouting materials which high strength, durability and environmentally safe materials for 2 types of suspension, solution grouting. The laboratory model tests such as permeation, solidification tests are performed to find injection effects by the injection pressure, soil condition. And environmental effects of the grouting materials is analyzed through the heavy-metal leaching tests. From the results, micro cement of suspension grouting superior permeation, solidification injection to Portland cement, and phosphoric acid and sodium hydrogen carbonate in solution grouting were similar to micro cement of suspension grouting. When compare to strength of grouted soils, micro cement of suspension grouting showed high compression strength to Portland cement. While, solution grouting showed very low compression strength comparing suspension grouting. Also, in the heavy-metal leaching tests results were satisfied with the environmental regulation standard for raw grouting materials and grouted soil by 7, 14, 28days curing.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1647-1654
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• 2008

The characteristics of arsenic(As) contamination were investigated on soils of 3 abandoned metal mine sites in Gangwon-do, Korea. Total forty nine soils were sampled to conduct standard methods(extraction by 1HCl), sequential extraction and column leaching test. Concentration of As extracted by 1N HCl was ordered as follows: A mine > B mine > C mine, and the concentration of arsenic in the soils of A mine was significantly greater than that at any other cases and all samples of A mine were exceeded the national regulation of $6mg \;kg^{-1}$. In the results of sequential extraction, the potential contamination risk for groundwater and plants was ordered as follows: C mine > B mine > A mine because the C mine showed the relatively greater mobility and bioavailability of fraction than any other mines. And, in colume test, concentration of As was ordered as follows: C mine > B mine > A mine, and it was expected that these results were connected with fraction characteristics of the mine sites. Therefore adequate leaching investigations should be used to simulate the effect of natural leaching conditions, and to predict both the potential mobility of metals to groundwater and their bioavailability to plants under natural conditions.