• Journal of Korean Society of Water and Wastewater
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• v.25 no.1
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• pp.1-5
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• 2011

Arsenic is one of the most abundant contaminant found in waste mine tailings and soil around refinery, Because of its carcinogenic property, the countries like United States of America and Europe have made stringent regulations which govern the concentration of arsenic in soil. The study focuses on solidification/stabilization for removal of arsenic from soil. Cement was used to solidify/stabilize the abandoned soil primarily contaminated with arsenic (up to 68.92 mg/kg) in and around refinery. Solidified/stabilized (s/s) forms in the range of cement contents 5-30 wt % were evaluated to determine the optimal binder content. Revised Korean standard leaching tests (KSLT), toxicity characteristic leaching procedures (TCLP), Old Korea standard leaching test and revised Korea standard leaching test were used for chemical characterization of the S/S forms. The addition of 10 % cement remarkably reduced the leachability of arsenic in contaminated soil. The concentration of As in leachate of TCLP, KSLT, and old KSLT for soil are below the standard. However that in leachate of revised KSLT is above the standard. Because of extraction fluid used in revised KSLT is very strong acid. It is arsenic in s/s with binder should be exhaustingly leached. Therefore S/S process would not be available for As treatment in soil in Korea.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.180-186
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• 2005

This paper discusses the development of mixtures for silica fume as a stabilization/solidification agent and a binder for industrial wastewater residue containing organic and heavy metal contaminants. The UCS (unconfined compressive strength) gradually increased to 66.7% as the silica fume content increased to 15%. The leaching of TOC (total organic carbon) and chromium decreased as more OPC (Ordinary Portland Cement) was substituted with the silica fume. When a mixture had 5% silica fume, it retained about 85% TOC, and chromium leached out 0.76 mg-Cr/g-Cr in acidic solution. Also, microstructural studies of the solidified analysis showed that the silica fume caused an inhibition to the ettringite formation which did not contrilbute to setting but coated the cement particles and retarded the setting reactions. The results indicated that the incorporation of silica fume into the cement matrix minimized the detrimental effects of organic materials on the cement hydration reaction and the contaminant leachability.

• Economic and Environmental Geology
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• v.37 no.3
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• pp.311-324
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• 2004

We investigated the contamination and behavior of heavy metals in stream sediments within the watershed of Juam Reservoir. Many abandoned mines within the reservoir can act as a potential contaminant source for water quality. Heavy metal concentrations (Cr, Cu, Ni, Pb and Zn) in stream sediments from watershed are very low, indicating that content of heavy metals in the sediments probably do not affect the water quality in Juam Reservoir. However Pb concentration in the stream sediments increases downward streams, suggesting the possible diffusion of Pb contamination. According to the leaching ratio for stream sediments at a strong acidic condition in the abandoned mine areas, the relative mobility for metals decreases in the order of Pb＞Zn=Cu＞Ni＞Cr, indicating that Pb can have a bad effect upon the water quality in Jum Reservoir. Moreover, if contaminated sediment is placed in the bottom of reservoir (i.e., reducing condition), the relative mobility of Pb is the highest, indicating that Pb in the bottom sediments can be leached to water at interface between water and sediment with changing in physicochemical conditions.

• Resources Recycling
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• v.13 no.4
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• pp.32-38
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• 2004

Recently, Orimulsion (a bitumen-in emulsion) has received increasing attention as an alternative fuel. Orimulsion combusion produces an ash rich in V, Ni and Mg which are processed to recover metals. As a basic study to recover V from Orimulsion ash, physico-chemcial properties and leaching behaviours were investigated. Orimulsion ash was fine size grains ($d_{50}$ 5.9 $\mu\textrm{m}$) with 16% V, 4 % Ni and 9% S. Vanadium was easily leached in water because Orimulsion ash was mainly constituted of metal sulfates. However, the increase of leaching temperature decreased the extraction percentage of vanadium because of hydrolysis of V(V) to vanadium pentoxide. The addition of sulfuric acid could increase the leaching percentage vanadium. In case of alkaline leaching for selective recovery of vanadium, the oxidzing agent such as $H_2$$O_2$ is required to improve the leaching per-centage

• Resources Recycling
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• v.27 no.4
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• pp.36-43
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• 2018

In order to recycle waste nickel-cadmium batteries, cadmium was selectively removed by ion substitution reaction so that cadmium and nickel could be separated efficiently. The electrode powder obtained by crushing the electrode in the waste nickelcadmium battery was leached with sulfuric acid. The cadmium in the nickel-cadmium solution was precipitated with cadmium sulfide by the addition of sodium sulfide. Ion substitution experiments were carried out under various conditions. At the optimum condition with pH = -0.1 and $Na_2S/Cd=2.3$ at room temperature, the residual Cd in the solution was about 100 ppm, and most of it was precipitated with CdS.

• Journal of Soil and Groundwater Environment
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• v.23 no.2
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• pp.23-29
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• 2018

This study explored secondary effects of the residual hydrofluoric acid (HF) after a hypothetical acid spill accident by investigating the long-term dissolution of minerals and leaching of pre-existing arsenic (As) from two soil samples (i.e., KBS and KBM) through batch and column experiments. An increase in the HF concentration in both soil samples resulted in a dramatic increase in the release of major cations, especially Si. However, the amounts of mineral dissolved were dependent on the soil type and mineral characteristics. Compared to the KBM soil, relatively more Ca, Mg and Si were dissolved from the KBS soil. The column experiment showed that the long-term dissolution rates of the minerals are closely associated with the acid buffering capacity of the two soils. The KBM soil had relatively higher effluent pH values compared to the KBS soil. Also, more As was leached from the KBM soil, with a more amorphous hydrous oxide-bound As fraction. These results suggest that the potential of heavy metal leaching by the residual acid after an acid spill will be influenced by heavy metal speciation and mineral structure in the affected soil.

• Environmental Engineering Research
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• v.24 no.1
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• pp.127-136
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• 2019

Land application of treated palm oil mill effluent (TPOME) could be used as an alternative tertiary wastewater treatment process. However, phenolic compounds in TPOME might be leached to the environment. This study investigated the ability of grasses on reducing phenolic compounds in the leachate after TPOME application. Several pasture grasses in soil pots were compared after irrigating with TPOME from stabilization ponds, which contained 360-630 mg/L phenolic compounds. The number of soil bacteria in planted pots increased over time with the average of $10^8CFU/g$ for mature grasses, while only $10^4-10^6CFU/g$ were found in the unplanted control pots. The leachates from TPOME irrigated grass pots contained lower amounts of phenolic compounds and had lower phytotoxicity than that of control pots. The phenol removal efficiency of grass pots was ranged 67-93% and depended on grass cultivars, initial concentration of phenolic compounds and frequency of irrigations. When compared to water irrigation, TPOME led to an increased phenolic compounds accumulation in grass tissues and decreased biomass of Brachiaria hybrid and Brachiaria humidicola but not Panicum maximum. Consequently, the application of TPOME could be conducted on grassland and the grass species should be selected based on the utilization of grass biomass afterward.

• 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.

• Journal of Korean Society on Water Environment
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• v.35 no.5
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• pp.409-417
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• 2019

In this study, a $480m^3/day$ pilot device was constructed through laboratory experiments based on the Ministry of Environment manual. The purpose of this study was to analyze the characteristics of CSO treatment and backwashing characteristics by applying the pilot device to the field. The purpose of this study was to acquire the basic data necessary for the design and operation management of the real scale filtration type non-point pollution control system. The filtration was conducted while maintaining the linear velocity of 20m/hour. The CSO treatment efficiencies of the pilot devices were 0.4-76.1%(mean 49.0 %), SS 51.4-91.6%(mean 77.8%), COD 22.2-59.4% (mean 38.3%) and TP 14.5-52.6%(mean 38.1%),respectively. The correlation coefficient between SS and the turbidity of influent water was 0.90, higher than that of CSO. To operate the treatment system effectively, the turbidity can be easily measured in real time as the monitoring item is the most appropriate because SS is the main target substance of the non-point source. As a result of analyzing the adsorbent treatment characteristics of PP filter material applied to this pilot device, the average particle diameter range of influent was $4.6-40.1{\mu}m$(mean $21.2{\mu}m$) and the treated water was $0.9-24.5{\mu}m$(mean $6.4{\mu}m$), respectively. Particles of approximately 10m or less are leached out, and so it is necessary to compensate for the raw water containing micro particulate matter.

• Korean Journal of Metals and Materials
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• v.50 no.12
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• pp.907-911
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• 2012

High purity silicon can be obtained from Al-Si alloys by a combination of solvent refining and centrifugation. Silicon purification by crystallization of silicon from an Al-Si alloy melt was carried out using 2N and 4N purity aluminum and 2N purity silicon as raw materials. The effect of the purity of raw materials on the final silicon ingot purity by centrifugation was investigated for an Al-50 wt% Si alloy. Alloys were melted using an electrical resistance furnace, and then poured into a centrifuging apparatus. A silicon lump like foam was obtained after centrifugation and was leached by an acid in order to get pure silicon flakes. Then silicon flakes were melted to make a silicon ingot using an induction furnace. The purities of the silicon flakes and silicon ingot were enhanced significantly compared to those of the raw materials of silicon and aluminum. The silicon ingot made of 4N aluminum and 2N silicon showed the lowest impurities.