• Korean Journal of Mineralogy and Petrology
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• v.33 no.1
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• pp.41-51
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• 2020

The purpose of this study was to investigate the possibility of eco-friendly/efficient recovery of valuable resources, such as Au from mine tailings, which are environmental pollutants in the Mongolian mine sector. For this purpose, this study selected 4 place of mine tailings of the Mongolian mines sector and carried out mineralogy evaluation of the valuable resources in the tailings. In this study, flotation was performed to separate and concentrate valuable resources in the tailings. Microwave nitric acid leaching was used to leach the valuable resources contained in the sample and to improve the Au grade. Chloride leaching attempted to leach Au from the leaching residues. XRD analysis of the tailings samples showed that most of the samples consisted of silicate minerals. As a result of confirming the content of the element through XRF analysis, the SiO₂ content was very high, the Fe₂O₃ content was 2.32-4.23%, and the content of PbO, CuO and ZnO components were all within 2%. As a result of flotation for the tailings samples, the recovery of Au was the highest in Bayanairag sample (95.38%). As a result of microwave nitric solution experiment on Au concentrate sample obtained by flotation, the content of Au in the microwave nitrate leaching residue increased by 12.15% from 192.72 g/ton to 216.14g/ton in Khamo sample, the highest increase was 57.58% in Bayanairag sample. TCLP tests on tailings generated after flotation showed dissolution characteristics within EPA. Chloride leaching test was performed to recover Au from solid residues. The leaching rate was 87.43-89.35% within 10 minutes. For Khamo sample, 100% Au was leached after 60 minutes of leaching time. Therefore, in order to process the tailings continuously generated in Mongolia, applying the same process as the present study is expected to effectively recover the valuable resources contained in the tailings.

• The Korean Journal of Pesticide Science
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• v.16 no.4
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• pp.315-321
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• 2012

Fate of acetamiprid and imidacloprid aerially sprayed to control pine wood nematode (Bursaphelenchus xylophilus) were studied in a forest of Haman area. Acetamiprid 20% SL or imidacloprid 20% DC were diluted 100 times and applied two times as rate of 50 L/ha using an aircraft of Bell 206 L helicopter. Average acetamiprid deposits on forest floor ranged from 2 to 4% of standard aerial application rate. Following to the second application, acetamiprid deposits in the pine needle ranged 1.8~8.5 mg/kg and then gradually decreased to 1.2~2.1 mg/kg after 48 days. Deposits on the plant washed off by rainfall and reached to soil surface was ca. 17% of the application rate. All of acetamiprid on the ground resided in the forest floor covering the soil surface, where acetamiprid residues were decreased to a quarter at 48 days after the second application, but they were not detected in soil beneath it. And the only low level of acetamiprid residues, 0.0003 mg/L, was detected in the reservoir nearby the experimental forest on the day of aerial application. The acetamiprid detection was presumably due to spray drift. And average imidacloprid deposits on forest floor ranged from 1 to 3% of standard aerial application rate. Following to the second application, imidacloprid deposits in the pine needle analysed very low concentration of 0.1 mg/kg, but the amount of imidacloprid in wash-off in standard and two-fold treatment were ca. 8% and 4% of the application rate, respectively. Most of imidacloprid on the ground also resided in the forest floor, where imidacloprid residues were decreased to a twentieth at 111 days after the second application, and they were detected below 0.5% of the application rate in sol beneath it. And the low level of imidacloprid, 0.0003~0.0017 mg/L, were detected in the streams in the experimental forest. It was not to the level of contamination concerns.

• Journal of fish pathology
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• v.20 no.2
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• pp.139-145
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• 2007

To decrease stress in eel (Anguilla japonica) during its culture or transportation, aspirin (ASA) known as analgesic, antiinflammatory and antithrombic agent was administrated by dipping or oral routes. Concentrations of aspirin (ASA) and salicylic acid (SA) in eel plasma were simultaneously measured by a high performance liquid chromatography (HPLC). The plasma was acidified with 0.2 M HCl and 0.2 M orthophosphoric acid, and mixed with acetonitrile. ASA and SA extracted with acetonitrile were analyzed by the HPLC equipped with reversed phase Novapak C18 column (4 ㎛ silica, 150×4 mm) and UV detector(237 nm). The mobile phase consisted of 740 ㎖ water, 900 ㎕ orthophosphoric acid (85%) and 180 ㎖ acetonitrile. The retention times of ASA, SA and 2-methylbenzoic acid(MBA) were 4.8 min, 8.4 min and 11.5 min, respectively. The limit of quantification was 0.01 ㎍/㎖ for SA and 0.05 ㎍/㎖ for ASA. The mean recovery from eel plasma was 70.8～99.6% for ASA and 95.2～100.3% for SA. This HPLC method was applied to analyze ASA and SA of eel plasma after either dipping in a concentration of 20 ppm or feeding the feed supplemented with 50 ㎎/kg BW. Only SA was detected in eel plasma after the administration of ASA by dipping or oral routes because the drug was quickly decomposed into SA in eel plasma. The amount of SA in eel plasma reached the highest value at 3hr in dipping and 7 days in oral administration. When the ASA-administrated eel were kept in ASA free aquaria, 0.02-0.03 ㎍/㎖ of SA were detected 48 hr after the administration in both routes.

• Journal of the Korean Ceramic Society
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• v.39 no.8
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• pp.801-806
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• 2002

The decomposition and/or conversion of carbon dioxide to carbon have been studied using oxygen-deficient ferrites for the reduction of $CO_2$ emission to the atmosphere. In this work, the homogeneous precipitation method using urea decomposition was employed to induce in situ precipitation of Ni ferrite($Ni_{0.4}Fe_{2.6}O_4$) on the porous ceramic fiber support (50 mm diameter${\times}$10 mm thickness). Effects of ferrite loading conditions on the CO2 decomposition efficiency were discussed in this paper. Removal of residual chloride ions and urea by solvent exchange from the porous media after ferrite deposition apparently helps to form spinel ferrite, but does not increase the efficiency of $CO_2$ decomposition. Porous ceramic fiber composites containing 20 wt% (1g) ferrite samples showed 100% efficiency for $CO_2$decomposition during the first three minutes, but the efficiency decreased rapidly after the elapsed time of ten minutes. The characteristic reduction time for the $CO_2$ decomposition efficiency was estimated as about 3∼7 min.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.8
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• pp.1227-1232
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• 2016

Electrolyzed activated water (EAW) has been reported to exhibit strong bactericidal effects on foodborne microorganisms. However, the disinfection efficacy of EAW is affected by factors such as water source and hardness. This study investigated bactericidal effects of EAW against three gram-positive (Bacillus cereus, Listeria monocytogenes, and Staphylococcus aureus) and three gram-negative (Cronobacter sakazakii, Escherichia coli O157:H7, and Salmonella Enteritidis) foodborne pathogens. Six strains were treated with EAW prepared at different water temperatures (4, 22, and $40^{\circ}C$) for 15 min, and D-values were generated. The results show that the lowest D-values for Lis. monocytogenes by EAW produced at $4^{\circ}C$ and $40^{\circ}C$ were 6.60 and 1.57 min, respectively. The lowest D-value for Sal. Enteritidis by EAW produced at $22^{\circ}C$ was 2.92 min. D-values of all strains treated by EAW produced at $40^{\circ}C$ decreased significantly compared to those treated by EAW produced at $4^{\circ}C$ (P<0.05). These results demonstrate that applying EAW produced at warm temperature is more effective for reducing foodborne pathogens for food safety.

• The Journal of the Korea Contents Association
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• v.19 no.11
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• pp.424-433
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• 2019

The purpose of this study was to evaluate the salivary concentration of Potassium and Magnesium cations and their variation before and after sucrose and glucose rinse, and to investigate the relationship between the levels of each compound. Saliva samples were obtained from 40 subjects before and up to 60 min after intake of a 10% sucrose and glucose solution at 1-month intervals. Potassium and Magnesium in human saliva were determined via anion-exchange chromatography with an anion-suppressed conductivity detector using 12 mM sulfuric acid. The concentrations of Potassium and Magnesium before sucrose rinse were 274.3±77.9 mg/ℓ and 4.5±2.5 mg/ℓ, also, the concentrations of Potassium and Magnesium before glucose rinse were 279.2±62.1 mg/ and 4.8±2.0 mg/ℓ, respectively. Potassium and Magnesium concentrations were significantly decreased (p<0.05) after sucrose rinse. The content of potassium and magnesium in saliva before and after rinsing sucrose and glucose is difficult to standardize or classify, as previous research. The reason for the variation between individuals is large, and easily changed by chemical or physiological stimulation. However, this study was experiment for the purpose of accumulating basic data for saliva.

• Proceedings of the Korean Society of Organic Agriculture Conference
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• 2009.12a
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• pp.304-305
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• 2009

시설재배지의 토양화학성 변화는 작물재배 기간 시비한 화학비료에서 유래된 무기성분 뿐만아니라, 가축분퇴비의 질소성분의 토양잔류량이 요소비료 보다 9.4배 많아 염류집적 주 요인이라는 보고('05 경기도)가 시사하는 봐와 같이 유기자원으로 시용하는 가축분 등의 부산물비료의 무기화에서 유래된 비료성분이 토양염류집적 및 토양환경악화에 더 큰 영향을 미칠 수 있다. 시설재배지의 유기물자원 시용기준이 토양의 특성에 관계 없이 작물에 따라 양적인 시험성적이 주로되어 있으며, 토양검정에 의한 시용기준도 유기물함량에 따라 볏짚, 우분, 돈분 및 계분으로 돠어 있다. 일반노지와 달리 시설재배지에서는 유기물함량이 토양의 비옥도 및 작물생육에 영향을 미치는 것 보다는 토양의 전기전도도(EC)가 더 중요한 작물생육 조건이 될 수 있다. 따라서 토양의 특성에 따라 물질순환에 의한 유기자원 시용기준으로 개선할 필요성이 있다. 시설재배지의 장기적인 토양관리를 위하여 유기물자원에 의한 토양환경 개선 효과를 구명하고자. 무처리, 가축분부산 물비료 관행 시용 기준 대비 볏짚 등 5개의 유기자원을 토양의 무기태질소 함량 대비 유기자원의 탄소함량을 C/N율 10 조절량을 시용하여 시험하였고, 또한 토양의 전기전도도(EC)가 상이한 3개( <2.0 dS/m, 2.0~6.0 dS/m, 6.0 dS/m<)토양에 유기물자원(우드칩)을 C/N율 10, 20, 30 조절하여 수박을 시험작물로 비닐하우스에서 재배하여 수행하였다. 시험 후 토양의 전기전도도(EC)는 시험 전에 비하여 시험 후 토양에서 가축분부산물비료는7% 증가되었으나 유기물자원 처리는 26~33% 경감되는 효과가 있었다. 수박의 과중은 무처리를 제외하고 처리간에 차이가 없었다. 유기물자원 C/N율 조절간에는 시험전 토양의 EC에 따라 차이가 있어 C/N 10 조절에서는 26~44%, C/N 20 조절에서는 30~51%, C/N 30 조절에서는 27~48% 경감효과가 있었으며, 3토양의 평균 토양EC 경감율은 C/N 10, 20, 30 조절에서 각각 34, 39 및 38 % 이었다. 수박의 생육 및 과중은 토양의 C/N율 조절간에는 차이가 없었으나, 토양의 EC 간에는 토양의 EC가 6.0dS/m 이상 토양에서 가장 낮았다. 따라서 탄소원의 유기자원을 C/N율 조절에 의한 시용기준 개선으로 토양의 무기태질소와 토양의 전기전도도(EC)를 경감시켜 친환경적 토양관리와 수박의 수량과 품질을 향상시킬 수 있을 것으로 평가되었다.

• Journal of the Korean Vacuum Society
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• v.21 no.6
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• pp.328-332
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• 2012

The work function of Ag (silver) is too low (~4.3 eV) to be used as an electrode of T-OLED (Top Emission Organic Light Emitting Diode). To solve this weakness, researches used plasma-, UV-, or thermal treatment on Ag films in order to increase the work function (~5.0 eV). So, most of studies have focused only on the work function of various treated Ag films, but studies focusing on nanomechanical properties were very important to investigate the efficiency and life time of T-OLED etc. In this paper, we focused on the mechanical properties of the Ag and $AgO_x$ film. The Ag was deposited on a glass substrate with the thickness of 150 nm by using rf-magnetron sputter with the power was fixed at 100 W and working pressure was 3 mTorr. The deposited Ag film was UV treated by UV lamp for several minutes (0~9 min). We measured the sheet resistance and mechanical property of the deposited film. From the experimental result, there were some differences of the sheet resistance and surface hardness of Ag thin film between short time (0~3 min) and long time UV treatment. These result presumed that the induced stress was taken place by the surface oxidation after UV treatment.

• Analytical Science and Technology
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• v.22 no.3
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• pp.272-276
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• 2009

This study was performed to investigate the disinfection efficiency and the generation characteristics of disinfection by-products (DBPs) in the sewage effluent. In the case of total coliforms, disinfection efficiency higher than 99%, the required contact time was 30 min at chlorine dose of 0.5 mg/L, 20 min at 1.0 mg/L, and 10 min at 1.5 mg/L, respectively. When the sewage effluent was disinfected with chlorine dose of 0.5 mg/L for 10 min, the maximum generation concentration of trihalomethanes (THMs), haloacetonitriles (HANs) and haloacetic acid (HAAs) were $32.2{\mu}g/L$, $2.97{\mu}g/L$, and $16.29{\mu}g/L$, respectively. The concentration of chloroform was $28.4{\mu}g/L$ corresponding to 88.1% of the THMs. The concentration of HANs and HAAs were found to be inconsiderable. The average residual chlorine concentration of sewage effluent was 0.4 mg/L, the generation concentration of THMs was maximum $1.72{\mu}g/L$ and average $2.79{\mu}g/L$. HANs and HAAs were under the detection limit by GC/MSD.

• Resources Recycling
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• v.32 no.6
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• pp.3-9
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• 2023

Separation of LED packages from PCBs and analysis of the adhesive components was conducted to enhance the recycling potential of LED modules. LED package was separated from PCBs using heat treatment under optimal conditions: temperature of above 250 ℃ and time of 20 minutes. The separation equipment can be established using a hot air injector with controlling the rotational speed of the internal screw. The separation efficiency of each type of substrate (aluminum and glass fiber) was investigated with the thickness range of the adhesive materials (0.25-0.30 and 0.30-0.35 mm). Under the optimal conditions, the efficiency can reach to 97.5% for both types of substrates with adhesive materials of thickness 0.25~0.30mm. Characterization of the residual adhesive substances from the separated LED package and PCB using microwave digestion and ICP analysis showed that the residue contained of 95% of Sn, less than 5% of Cu and Ag.