• Journal of the Mineralogical Society of Korea
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• v.23 no.3
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• pp.235-242
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• 2010

Froth flotation using the residual water in the end of flotation process has been performed through controlling of pH. IEP (isoelectric point) of molybdenite and quartz in distilled water was below pH 3 and pH 2.7, respectively and the stabilized range was pH 5~10. In case of a suspension in reusing water, zeta potential of molybdenite decreased to below -10 mV or less at over pH 4 due to residual flocculants. As result of pH control, flotation efficiency in the alkaline conditions was deteriorated by flocculation, resulting from expanded polymer chain, ion bridge of the divalent metal cations ($Ca^{2+}$), and hydrophobic interactions between the nonpolar site of polymer/the hydrophobic areas of the particle surfaces. However, the weak acid conditions (pH 5.5~6) improved the efficiency of flotation as hydrogen ions neutralize polymer chains and then weakened its function. In cleans after rougher flotation, the Mo grade of 52.7% and recovery of 90.1% could be successfully obtained under the conditions of 20 g/t kerosene, 50 g/t AF65, 300 g/t $Na_2SiO_3$, pH 5.5 and 2 cleaning times. Hence, we developed a technique which can continuously supply waste water filtered from tailings into the grinding-rougher-cleaning processes.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.9 no.2
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• pp.63-71
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• 2011

A large volume of uranium electrokinetic leachate has been generated during the electrokinetic decontamination to remove uranium from contaminated soil. The treatment technology for the reuse of the uranium leachate was developed. The concentration of uranium in the generated uranium leachate was 180 ppm and concentrations of Mg(II), K(I), Fe(II), and Al(III) ions ranged from 20 ppm to 1,210 ppm. The treatment process for uranium leachate consisted mainly of mixing and cohesion, precipitation, concentration, and filtration. In order to obtain the pH=11 of a precipitate solution, the calcium hydroxide needs to be 3.0g/100ml and the sodium hydroxide needed to be 2.7g/100ml. The results of several precipitation experiments showed that a mixture of NaOH+0.2g alum+0.15g magnetite was an optimal precipitant for filtration. The average particle size of precipitate with NaOH+alum+0.15g magnetite was $600\;{\mu}m$. Because the total value of metal concentrations in supernatant at pH=9 was the smallest, sodium hydroxide should be added with 0.2g alum and 0.15g magnetite for pH=9 of leachate.

• Journal of the Mineralogical Society of Korea
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• v.32 no.3
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• pp.185-200
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• 2019

This study aimed to liberate gold from invisible gold concentrate (Au = 1,840.00 g/t) through microwave nitric acid leaching experiments. For the purpose, this study conducted microwave-nitric acid leaching experiments and examined nitric acid concentration effect, microwave leaching time effect and sample addition effect. The results of the experiments were as follows: Au (gold) contents were not detected in all of the microwave leaching conditions. In the insoluble-residue, weight loss rate tended to decrease as the nitric acid concentration, microwave leaching time and sample addition increased. In an XRD analysis with solid-residue, it was suggested that gypsum and anglesite were formed due to dissolution of calcite and galena by nitric acid solution. When a fire assay was carried out with insoluble-residue, it was discovered that gold contents of the solid-residue were 1.3 (Au = 2,464.70 g/t) and 28.8 (52,952.80 g/t) times more than those of concentrate. But in the gold contents recovered, a severe gold nugget effect appeared. It is expected that the gold nugget effect will decrease if a sampling method of concentrate is improved in the microwave-nitric acid leaching experiments and filtering paper with smaller pore size is used for leaching solution and burned filter paper is used for sampling in lead-fire assay.

• The Korean Journal of Nuclear Medicine
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• v.32 no.3
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• pp.298-304
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• 1998

Purpose: We evaluated the usefulness of Re-188 sulfur colloid for radiation synovectomy and therapy of intraperitoneal metastasis. Materials and Methods: We investigated the labeling efficiency of Re-188 sulfur colloid on various conditions. The stability of Re-188 sulfur colloid was observed at room temperature for 24 h and in human serum and synovial fluid for 72 h. The particle size distribution of Re-188 sulfur colloid was measured by filtering with various pore size filters. Animal experiment was performed in mice and rabbits. Results: The labeling efficiency of Re-188 sulfur colloid was $64.5{\pm}5.8%$ (n=5) at the conditions of sodium thiosulfate 40 mg, EDTA $Na_2.2H_2O$ 0.8 mg, $KReO_4$ 0.8 mg at pH 1. After purification, the radiochemical purity was higher than 99%. The stability of Re-188 sulfur colloid was high (>99%) at room temperature for 24 h and in human serum and synovial fluid for 72 h. The particle size distribution of Re-188 sulfur colloid was 0.3% ($<1{\mu}m$), 11.2% ($1{\sim}5{\mu}m$), 25.8% ($5{\sim}10{\mu}m$) and 52.8% ($>10{\mu}m$). In mice, 1 h postinjection of Re-188 sulfur colloid into tail vein, uptakes in lung, liver and muscle were $37.30{\pm}5.36$, $32.33{\pm}1.79$, $6.60{\pm}0.02%$ ID/organ respectively. After i.p. injection in mice, the uptakes of extraperitonial organs of Re-188 sulfur colloid at 1 and 24 h were $0.1{\pm}0.1$, $0.4{\pm}0.1%$ ID/organ, and the excretions through urine and feces (${\sim}70 h$) were low ($2.68{\pm}0.80$, $0.95{\pm}0.17%$). When Re-188 sulfur colloid was injected to synovial space of rabbit, the uptake in other organs except knee was very low. Conclusion: Re-188 sulfur colloid showed high labeling efficiency, stability and potency for clinical use.

• Korean Journal of Ecology and Environment
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• v.44 no.1
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• pp.31-41
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• 2011

To optimize the natural chemical agents against nuisance phytoplankton, we examined algal removal activity (ABA) of Plant-Mineral Composite (PMC), which already developed by our teams (Kim et al., 2010), on various conditions. The PMC are consisted of extracted-mixtures with indigenous plants (Camellia sinensis, Quercusacutissima and Castanea crenata) and minerals (Loess, Quartz porphyry, and natural zeolite), and characterized by coagulation and floating of low-density suspended solids. A simple extraction process was adopted, such as drying and grinding of raw material, water-extraction by high temperature-sonication and filtering. All tests were performed in 3 L plastic chambers varying conditions; six different concentrations ($0{\sim}1.0\;mL\;L^{-1}$), six light intensities ($8{\sim}1,400\;{\mu}mol\;m^{-2}s^{-1}$), three temperatures ($10{\sim}30^{\circ}C$), four pHs (7~10), five water depths (10~50 cm), and three different waters dominated by cyanobacteria, diatom, and green algae, respectively. Results indicate that the highest ABA of PMC was seen at $0.05\;mL\;L^{-1}$ in treatment concentrations, where showed a reduction of more than 80% of control phytoplankton biomass, while $1,400\;{\mu}mol\;m^{-2}s^{-1}$ in light intensity (>90%), $20{\sim}30^{\circ}C$ temperature (>60%), 7~9 in pH (>90%), below 50 cm in water depth (>90%), and cyanobacterial dominating waters (>80%), respectively. Over the test, ABA of PMC were more obvious on the algal biomass (chlorophyll-${\alpha}$) than suspended solids, suggesting a selectivity of PMC to particle size or natures. These results suggest that PMC agents can play an important role as natural agents to remove the nuisant algal aggregates or seston of eutrophic lake, where occur cyanobacterial bloom in a shallow shore of lake during warm season.

• Journal of the Korean Society of Groundwater Environment
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• v.7 no.3
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• pp.103-115
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• 2000

The formation of brown-colored precipitates is one of the serious problems frequently encountered in the development and supply of groundwater in Korea, because by it the water exceeds the drinking water standard in terms of color. taste. turbidity and dissolved iron concentration and of often results in scaling problem within the water supplying system. In groundwaters from the Pajoo area, brown precipitates are typically formed in a few hours after pumping-out. In this paper we examine the process of the brown precipitates' formation using the equilibrium thermodynamic and kinetic approaches, in order to understand the origin and geochemical pathway of the generation of turbidity in groundwater. The results of this study are used to suggest not only the proper pumping technique to minimize the formation of precipitates but also the optimal design of water treatment methods to improve the water quality. The bed-rock groundwater in the Pajoo area belongs to the Ca-$HCO_3$type that was evolved through water/rock (gneiss) interaction. Based on SEM-EDS and XRD analyses, the precipitates are identified as an amorphous, Fe-bearing oxides or hydroxides. By the use of multi-step filtration with pore sizes of 6, 4, 1, 0.45 and 0.2 $\mu\textrm{m}$, the precipitates mostly fall in the colloidal size (1 to 0.45 $\mu\textrm{m}$) but are concentrated (about 81%) in the range of 1 to 6 $\mu\textrm{m}$in teams of mass (weight) distribution. Large amounts of dissolved iron were possibly originated from dissolution of clinochlore in cataclasite which contains high amounts of Fe (up to 3 wt.%). The calculation of saturation index (using a computer code PHREEQC), as well as the examination of pH-Eh stability relations, also indicate that the final precipitates are Fe-oxy-hydroxide that is formed by the change of water chemistry (mainly, oxidation) due to the exposure to oxygen during the pumping-out of Fe(II)-bearing, reduced groundwater. After pumping-out, the groundwater shows the progressive decreases of pH, DO and alkalinity with elapsed time. However, turbidity increases and then decreases with time. The decrease of dissolved Fe concentration as a function of elapsed time after pumping-out is expressed as a regression equation Fe(II)=10.l exp(-0.0009t). The oxidation reaction due to the influx of free oxygen during the pumping and storage of groundwater results in the formation of brown precipitates, which is dependent on time, $Po_2$and pH. In order to obtain drinkable water quality, therefore, the precipitates should be removed by filtering after the stepwise storage and aeration in tanks with sufficient volume for sufficient time. Particle size distribution data also suggest that step-wise filtration would be cost-effective. To minimize the scaling within wells, the continued (if possible) pumping within the optimum pumping rate is recommended because this technique will be most effective for minimizing the mixing between deep Fe(II)-rich water and shallow $O_2$-rich water. The simultaneous pumping of shallow $O_2$-rich water in different wells is also recommended.