• Title/Summary/Keyword: Ion concentration

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Luminescence Characteristics of (Y0.85-xYb0.15)3Ga5O12:Er3+x Phosphors ((Y0.85-xYb0.15)3Ga5O12:Er3+x 형광체의 형광특성)

  • Chung, Jong Won;Yi, Soung Soo
    • New Physics: Sae Mulli
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    • v.68 no.12
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    • pp.1308-1314
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    • 2018
  • $Er^{3+}$ and $Yb^{3+}$ co-doped $Y_3Ga_5O_{12}$ polycrystalline powders were prepared by using a solid-state reaction method, and their crystallinities were measured using X-ray diffraction. According to the results of X-ray diffraction, the powders showed a polycrystalline tetragonal structure. The photoluminescence and the upconversion luminescence properties of the $(Y_{0.85-x}Yb_{0.15})_3Ga_5O_{12}:Er^{3+}_x$ (x = 0.03, 0.06, 0.09, 0.12 and 0.15) phosphors were investigated in detail. Green and red upconversion emissions were observed for the phosphors excited by 980 nm radiation from a semiconductor laser. The powders exhibited strong green and weak red upconversion emission peaks at 553 and 660 nm, respectively. Also, their upconversion processes were explained using an energy-diagram analysis and the strongest upconversion intensity was emitted by the powder with a 0.12 mol $Er^{3+}$ ion concentration.

Influence of Bacterial Attachment on Arsenic Bioleaching from Mine Tailings: Dependency on the Ratio of Bacteria-Solid Substrate (광물찌꺼기 내 비소의 미생물 침출 시 박테리아 흡착 영향: 박테리아와 고체 기질 비율에 관한 연구)

  • Park, Jeonghyun;Silva, Rene A.;Choi, Sowon;Ilyas, Sadia;Kim, Hyunjung
    • Resources Recycling
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    • v.30 no.3
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    • pp.30-40
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    • 2021
  • The present study investigates the bioleaching efficiencies of arsenic via contact and non-contact mechanisms. The attachment of Acidithiobacillus ferrooxidans was restricted by a partition system comprising a semi-permeable membrane with a molecular weight cutoff of 12-14 kDa. The results were compared for two arsenic concentrations in the system (1.0% and 0.5% w/v) to maintain a homogeneous system. The overall bacterial performance was monitored by comparing total arsenic and iron concentrations, Fe ion speciation, pH, and solution redox potentials in flask bioleaching experiments over a period of 10 d. Our results indicated that bacterial attachment could increase arsenic extraction efficiency from 20.0% to 44.9% at 1.0 % solid concentrations. These findings suggest that the bacterial contact mechanism greatly influences arsenic bioleaching from mine tailings. Therefore, systems involving two-step or non-contact bioleaching are less effective than those involving one-step or contact bioleaching for the efficient extraction of arsenic from mine tailings.

Synthesis and Characterization of Collagen Peptide Based Copolymer from Shaving Scrap (셰이빙 스크랩으로부터 콜라겐 펩타이드계 공중합체 합성과 특성)

  • Park, Min Seok;Shin, Soo Beom;Kim, Ho Soo;Kim, Min Soo;Kim, Ha Sun;Jang, Jae Hyeok;Lee, Jin Kye;Lee, Dong Kuk
    • Applied Chemistry for Engineering
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    • v.33 no.6
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    • pp.581-587
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    • 2022
  • The leather industry generates a large amount of hazardous leather waste of various types every year. Among them, shaving scrap is difficult to recycle because it contains chromium ions. Many studies in recent years have shown that shaving scraps can be processed into various types of valuable products, such as adsorbent, filler, and poultry feed. In this study, collagen peptides were extracted from shaving scraps and structurally modified to be developed as new materials with improved physicochemical properties. First, the chromium ions contained in the shaving scraps were removed using a sodium hydroxide solution, and purified through concentration and low-temperature crystallization. The purified collagen peptide was used to prepare the powder using a spray dryer. The extracted collagen peptides were structurally modified by introducing double bonds by reacting with methacrylic anhydride (MAA), and the product was confirmed by 1H NMR spectroscopy. Next, a copolymer was prepared by redox polymerization of the modified collagen peptide (MCP) and 2-ethylhexyl acrylate (2-EHA). The structure of the copolymer was qualitatively confirmed by FT-IR. In conclusion, this study confirmed that collagen peptides can be extracted from shaving scrap and converted into new eco-friendly materials through certain treatments.

Prediction of Chemical Acceleration Durability Time of Polymer Membrane in Polymer Electrolyte Membrane Fuel Cells (고분자 전해질 연료전지에서 고분자막의 화학적 가속 내구 시간 예측)

  • Sohyeong Oh;Donggeun Yoo;Sunggi Jung;Jihong Jeong;Kwonpil Park
    • Korean Chemical Engineering Research
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    • v.61 no.1
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    • pp.26-31
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    • 2023
  • For durability improvement of polymer electrolyte membrane fuel cell (PEMFC) polymer membrane, accelerated durability evaluation methods that can evaluate durability in a short time have been researched and developed. However, the lifespan of fuel cells for large commercial vehicles such as trucks and buses is more than three times that of passenger cars, and the chemical accelerated stress test (AST) time is also longer, reaching 1,500 hours or more. Therefore, in this study, as a method to evaluate the chemical durability of a membrane within a short time, it was examined whether the durability could be predicted by the pristine membrane characteristics. Hydrogen crossover current density (HCCD) and short resistance (SR) were estimated as initial characteristics, and AST time was predicted through the Fenton experiment, which was possible as an out-of-cell experiment for 3 hours. As the HCCD and fluoride ion emission concentration increased, the AST time tended to be linearly shortened, but there was a deviation (R2 ≒0.65). When the SR decreased, the AST time showed a linear increase, and the accuracy was high (R2 =0.93), so the AST time could be predicted with the initial SR of the membrane.

Structural and Electrical Properties of (La0.7-xCex)Sr0.3MnO3 Ceramics ((La0.7-xCex)Sr0.3MnO3 세라믹스의 구조적, 전기적 특성)

  • Tae-Yeon In;Jeong-Eun Lim;Byeong-Jun Park;Sam-Haeng Yi;Myung-Gyu Lee;Joo-Seok Park;Sung-Gap Lee
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.36 no.3
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    • pp.249-254
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    • 2023
  • La0.7-xCexSr0.3MnO3 specimens were fabricated by a solid state reaction method and structural and electrical properties with variation of Ce4+ contents were measured. All specimens exhibited a polycrystalline rhombohedral crystal structure, and the (110) peaks were shifted to low angle side with increasing the amount of Ce4+ contents. As Ce4+ ions with different ion radii and charges are substituted with La3+ ions, electrical properties are thought to be affected by changes in the double exchange interaction between Mn3+-Mn4+ ions due to distortion of the unit lattice, a decrease in oxygen vacancy concentration, and an increase in lattice defects. Resistivity gradually decrease as the amount of Ce4+ added increased, and negative temperature coefficient of resistance (NTCR) properties were shown in all specimens. In the La0.5Ce0.2Sr0.3MnO3 specimens, electrical resistivity, TCR and B-value were 31.8 Ω-cm, 0.55%/℃ and 605 K, respectively.

High-purity Lithium Carbonate Manufacturing Technology from the Secondary Battery Recycling Waste using D2EHPA + TBP Solvent (이차전지 폐액으로부터 D2EHPA + TBP solvent를 활용한 탄산리튬 제조기술)

  • Dipak Sen;Hee-Yul Yang;Se-Chul Hong
    • Resources Recycling
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    • v.32 no.1
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    • pp.21-32
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    • 2023
  • Because the application of lithium has gradually increased for the production of lithium ion batteries (LIBs), more research studies about recycling using solvent extraction (SX) should focus on Li+ recovery from the waste solution obtained after the removal of the valuable metals nickel, cobalt and manganese (NCM). The raffinate obtained after the removal of NCM metal contains lithium ions and other impurities such as Na ions. In this study, we optimized a selective SX system using di-(2-ethylhexyl) phosphoric acid (D2EHPA) as the extractant and tri-n-butyl phosphate (TBP) as a modifier in kerosene for the recovery of lithium from a waste solution containing lithium and a high concentration of sodium (Li+ = 0.5 ~ 1 wt%, Na+ = 3 ~6.5 wt%). The extraction of lithium was tested in different solvent compositions and the most effective extraction occurred in the solution composed of 20% D2EHPA + 20% TBP + and 60% kerosene. In this SX system with added NaOH for saponification, more than 95% lithium was selectively extracted in four extraction steps using an organic to aqueous ratio of 5:1 and an equilibrium pH of 4 ~ 4.5. Additionally, most of the Na+ (92% by weight) remained in the raffinate. The extracted lithium is stripped using 8 wt% HCl to yield pure lithium chloride with negligible Na content. The lithium chloride is subsequently treated with high purity ammonium bicarbonate to afford lithium carbonate powder. Finally the lithium carbonate is washed with an adequate amount of water to remove trace amounts of sodium resulting in highly pure lithium carbonate powder (purity > 99.2%).

Development of novel oxyfluoride glasses and glass ceramics for photoluminescence material by a containerless processing (무용기 용융법을 활용한 형광소재용 결정화 유리 개발)

  • Hyerin Jo;Minsung Hwang;Youngjin Lee;Jaeyeop Chung
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.33 no.5
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    • pp.181-186
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    • 2023
  • In this study, novel Eu2O3-BaF2-La2O3-B2O3 oxyfluoride glasses and glass ceramics were developed by a containerless processing. Differential thermal analysis (DTA) analysis was performed to analyze the thermophysical properties of oxyfluoride glasses doped with Eu2O3, and photoluminescence (PL) characteristics were analyzed to evaluate the luminous efficiency depending on the degree of crystallinity. The glass transition temperature decreased with increasing BaF2 concentration since BaF2 acts as a network modifier in this glass system. In addition, thermal stability which can be estimated by the difference between the glass transition temperature and the onset temperature of the crystallization decreased with increasing BaF2 contents. The peak related to the BaF2 crystal was confirmed after the crystallization by X-ray Diffraction (XRD) analysis. Photoluminescence intensity increased after the crystallization which indicates that the Eu3+ ions are sited in BaF2 crystal. La 3d5/2 x-ray photoelectron spectroscopy (XPS) and F1s XPS spectra were analyzed to precisely understand the behavior of the fluorine ion in the glass structure. Fluorine tends to bond with the network modifying cations such as La3+ and Ba2+ ions and after the crystallization the La-F bonds decreased because F- ions used to form BaF2 crystals.

Performance improvement of artificial neural network based water quality prediction model using explainable artificial intelligence technology (설명가능한 인공지능 기술을 이용한 인공신경망 기반 수질예측 모델의 성능향상)

  • Lee, Won Jin;Lee, Eui Hoon
    • Journal of Korea Water Resources Association
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    • v.56 no.11
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    • pp.801-813
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    • 2023
  • Recently, as studies about Artificial Neural Network (ANN) are actively progressing, studies for predicting water quality of rivers using ANN are being conducted. However, it is difficult to analyze the operation process inside ANN, because ANN is form of Black-box. Although eXplainable Artificial Intelligence (XAI) is used to analyze the computational process of ANN, research using XAI technology in the field of water resources is insufficient. This study analyzed Multi Layer Perceptron (MLP) to predict Water Temperature (WT), Dissolved Oxygen (DO), hydrogen ion concentration (pH) and Chlorophyll-a (Chl-a) at the Dasan water quality observatory in the Nakdong river using Layer-wise Relevance Propagation (LRP) among XAI technologies. The MLP that learned water quality was analyzed using LRP to select the optimal input data to predict water quality, and the prediction results of the MLP learned using the optimal input data were analyzed. As a result of selecting the optimal input data using LRP, the prediction accuracy of MLP, which learned the input data except daily precipitation in the surrounding area, was the highest. Looking at the analysis of MLP's DO prediction results, it was analyzed that the pH and DO a had large influence at the highest point, and the effect of WT was large at the lowest point.

A Study on the Prior Leaching and Recovery of Lithium from the Spent LiFePO4 Cathode Powder Using Strong Organic Acid (강유기산을 이용한 폐LiFePO4 양극분말로부터 리튬의 선침출에 대한 연구)

  • Dae-Weon Kim;Soo-Hyun Ban;Hee-Seon Kim;Jun-Mo Ahn
    • Clean Technology
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    • v.30 no.2
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    • pp.105-112
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    • 2024
  • Globally, the demand for electric vehicles has surged due to greenhouse gas regulations related to climate change, leading to an increase in the production of used batteries as a consequence of the battery life issue. This study aims to selectively leach and recover valuable metal lithium from the cathode material of spent LFP (LiFePO4) batteries among lithium-ion batteries. Generally, the use of inorganic acids results in the emission of toxic gases or the generation of large quantities of wastewater, causing environmental issues. To address this, research is being conducted to leach lithium using organic acids and other leaching agents. In this study, selective leaching was performed using the organic acid methane sulfonic acid (MSA, CH3SO3H). Experiments were conducted to determine the optimal conditions for selectively leaching lithium by varying the MSA concentration, pulp density, and hydrogen peroxide dosage. The results of this study showed that lithium was leached at approximately 100%, while iron and phosphorus components were leached at about 1%, verifying the leaching efficiency and the leaching rates of the main components under different variables.

Cesium Adsorption Properties of Activated Carbon with Oxygen Functional Groups Introduced by Ozonation Treatment (오존 처리에 의해 산소 작용기가 도입된 활성탄소의 세슘 흡착 특성)

  • Eunseon Chae;Chung Gi Min;Chaehun Lim;Young-Seak Lee
    • Applied Chemistry for Engineering
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    • v.35 no.1
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    • pp.23-28
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    • 2024
  • Cesium is a potential toxic contaminant due to its high solubility, which allows it to easily penetrate the human body and potentially induce cancer or DNA mutations. In this study, oxygen functional groups were introduced on activated carbons (ACs) by ozone treatment to enhance the cesium adsorption capacity. As the ozone treatment time increased, the oxygen content on the ACs surface increased. Subsequently, the electrostatic interaction between ACs and cesium enhanced, resulting in higher cesium ion adsorption efficiency across all samples. In particular, the sample treated with ozone for 7 minutes at an internal ozone concentration of 50000 ppm had roughly 12% greater oxygen functional group content and the highest cesium removal effectiveness (97.6%). Meanwhile, samples treated for 5 minutes showed a 0.3% cesium removal rate difference compared to those treated for 7 minutes, which was caused by the surface chemical similarity of the two samples due to the reactive characteristics of ozone gas. However, the cesium adsorption performance of ozonated activated carbon seems to be mainly influenced by the amount of oxygen functional groups introduced to the surface, although the specific surface area and pore structure of the activated carbon are also important.