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Bolam Kim,Gi-Taek Oh,Youngsu Lim,Jinseob Kim,Juhui Park,Seongju Lee,Jiseon Jang,Seho Choi,Myunggoo Kang,Jaechul Ha,Chun-Hyung Cho,Min-Woo Lee,Dae Sung Lee 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1
The organic complexing agents such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and isosaccharinic acid (ISA) can enhance the radionuclides’ solubility and have the potential to induce the acceleration of radionuclides’ mobility to a far-field from the radioactive waste repository. Hence, it is essential to evaluate the effect of organic complexing agents on radionuclide solubility through experimental analysis under similar conditions to those at the radioactive waste disposal site. In this study, five radionuclides (cesium, cobalt, strontium, iodine, and uranium) and three organic complexing agents (EDTA, NTA, and ISA) were selected as model substances. To simulate environmental conditions, the groundwater was collected near the repository and applied for solubility experiments. The solubility experiments were carried out under various ranges of pHs (7, 9, 11, and 13), temperatures (10°C, 20°C, and 40°C), and concentrations of organic complexing agents (0, 10-5, 10-4, 10-3, and 10-2 M). Experimental results showed that the presence of organic complexing agents significantly increased the solubility of the radionuclides. Cobalt and strontium had high solubility enhancement factors, even at low concentrations of organic complexing agents. We also developed a support vector machine (SVM) model using some of the experimental data and validated it using the rest of the solubility data. The root mean square error (RMSE) in the training and validation sets was 0.012 and 0.016, respectively. The SVM model allowed us to estimate the solubility value under untested conditions (e.g., pH 12, temperature 30°C, ISA 5×10-4 M). Therefore, our experimental solubility data and the SVM model can be used to predict radionuclide solubility and solubility enhancement by organic complexing agents under various conditions.
Rapid and Automated Quantification of Microalgal Lipids on a Spinning Disc
Kim, Yubin,Jeong, Su-Nam,Kim, Bolam,Kim, Dong-Pyo,Cho, Yoon-Kyoung American Chemical Society 2015 ANALYTICAL CHEMISTRY - Vol.87 No.15
<P>We have developed a fully integrated centrifugal microfluidic device for rapid on-site quantification of lipids from microalgal samples. The fully automated serial process involving cell sedimentation and lysis, liquid–liquid extraction, and colorimetric detection of lipid contents was accomplished within 13 min using a lab-on-a-disc. The presented organic solvent-tolerable (for <I>n</I>-hexane, ethanol) microfluidic disc was newly fabricated by combining thermal fusion bonding and carbon dot-based valving techniques. It is expected that this novel platform will possibly contribute toward sustainable biofuel applications by providing a practical solution for on-site monitoring of lipid accumulation in microalgal samples, thus providing imperative contribution toward energy and environmental purposes of centrifugal microfluidic technology.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2015/ancham.2015.87.issue-15/acs.analchem.5b01570/production/images/medium/ac-2015-01570q_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac5b01570'>ACS Electronic Supporting Info</A></P>
Bolam Kim,Jiseon Jang,Seho Choi,Myunggoo Kang,Jaechul Ha,Chun-Hyung Cho,Sanghwa Oh,Dae Sung Lee 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2
Cellulose-based wastes can be degraded into short-chain organic acids at the cementitious radioactive waste repository. Isosaccharinic acid (ISA), one of the main degradation products, can form the chelate complex with metals and radionuclides, and these complexes have a potential that can accelerate to move the radionuclides to far-field from the repository. This study characterized the amount of generated ISA from typical cellulosic materials in the repository. Two different degradation experiments were conducted under alkaline conditions (saturated with Ca(OH)2 at pH 12.4): i) cellulosic material mixture under an opened condition (partially aerobic), and ii) cellulosic material under an anaerobic condition in a nitrogen-purged glove box. In the first case, three different types of cellulosic materials–paper, cotton, and wood– were mixed at the same ratio, and the experiments were carried out at three different temperatures (20°C, 40°C, and 60°C). It revealed that both the cellulose degradation rate and generated ISA concentration were high at high reaction temperatures, and various soluble degradation products such as formic acid and lactic acid were generated. The cellulose degradation in this work seems to still stay at a peeling-off process. In the second study, each type of cellulosic material was applied in its own batch experiments, and the amount of generated ISA was in the order of paper > wood > cotton. The above two experiments are supposed to be a long-term study until the generated ISA reaches an equilibrium state.
Solubility of Radionuclides Under Near and Far Field Conditions: Effect of Organic Complexing Agents
Bolam Kim,Ahsan Abdul Ghani,Youngsu Lim,Dae Sung Lee 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2
Organic complexing agents which are contained in the radioactive waste can form the complex with radionuclides and enhance the solubility of radionuclides. The mobility of radionuclides to the far-field from the repository will be increased by radionuclide-ligand complex formation. Therefore, the assessment of the radionuclides’ solubility should be performed in the presence of organic complexing agents. In this study, five radionuclides (cobalt, strontium, iodine, cesium, and uranium) and three organic complexing agents (ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and isosaccharinic acid (ISA)) were selected as model radionuclides and organic complexing agents, respectively. For simulating the in-situ condition, the groundwater near the repository was collected and applied in solubility experiments and the solubility was measured in various environmental conditions such as different pHs (7, 9, 11, and 13), temperatures (10°C, 20°C, and 40°C), and a range of organic complexing agent concentrations (10-5, 10-4, 10-3, and 10-2 M). In cases of cesium and iodine, they were very soluble in all conditions, and the effect on their solubilities was not observed. However, at high pHs, cobalt and strontium showed lower solubilities than at neutral pH and the solubility enhancement by the organic complexing agents was significant. Moreover, the effects of each organic ligand showed obvious differences and were in the order of EDTA > NTA > ISA. The solubility of uranium was increased with increasing the organic ligand concentration at lower pHs, but the organic complexing agents did not cause a remarkable difference at high pHs. According to these results, the presence of complexing agents could enhance the radionuclides’ solubility and increase the potential to release the radionuclides to the far-field from the repository. Solubility experiments of other major radionuclides in the repository are in progress.
Sorption of Organic Complexing Agents to Engineering Barriers of a Radioactive Waste Disposal Site
Jinseob Kim,Ahsan Abdul Ghani,Bolam Kim,Youngsu Lim,Dae Sung Lee 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2
Organic complexing agents may affect the mobility of radionuclides at low- and intermediate-level radioactive waste repositories. Especially, isosaccharinic acid (ISA) is the main cellulose degradation product under high pH conditions in cement pore water. ISA can combine with radionuclides and form stable complexes that adversely influence adsorption in the concrete phase, resulting in radionuclides to leach to the near- and far-fields of repositories. This study focuses on investigating the sorption of ISA onto engineered barriers such as concrete, thereby studying adsorption isotherms of ISA on concrete and comparing various isotherm models with the experimental data. The adsorption experiment was conducted in three background solutions, groundwater (adjusted to pH 13 using NaOH), State 1 (artificial cement pore water, pH 13.3), and State 2 (artificial cement pore water, pH 12.5), in a batch system at a temperature of 20°C. Concrete was characterized using BET, Zeta-potential analyzer, XRD, XRF, and SEM-EDS. ISA concentrations were detected using HPLC. The experimental data were best fitted to one-site Langmuir isotherm; On the other hand, either two-site isotherm or Freundlich isotherm couldn’t give reasonable fitting to the experimental data. The observed ISA sorption behavior on concrete is crucial for the disposal of radioactive waste because it can significantly lower the concentration of ISA in the pore water. Although one-site Langmuir isotherm might effectively represent the sorption behavior of ISA on concrete, the underlying mechanism is still unknown, and further investigation should be done in the near future.
Seongsu Kang,Bolam Kim,Se-Jun Yim,Jin-Oh Kim,Dong-Pyo Kim,Yeu-Chun Kim 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.88 No.-
Electroporation technique has recently emerged as a tool for delivery of foreign molecules into cells. However, the electroporation has many critical hurdles to overcome in cell viability, delivery efficiency,and productivity. To overcome the hurdles with a single platform, we devised a polyimide (PI)film-basedon- chip electroporation system that shields the cells from the electrodes with four sheathflows,enabling a 3Dflow focusing. This on-chip electroporation with a double forced-flow (OE-DFF)configuration enhances the cell viability to such an extent that even with a long spiral channel for highmolecular delivery efficiency, which is detrimental to the cell viability due to longer exposure to theelectricfield, the cell viability is still increased substantially. The advantages provided by the OE-DFFsystem is demonstrated with afluorescent probe molecule (FITC-BSA) and pPtCrCFP plasmid deliveredinto Chlamydomonas reinhardtii, one of the challenging cell lines to transform. The continuous nature oftheflow system assures high throughput. This novel approach in microfluidic science is expected togreatly contribute to algal research as an efficient electroporation tool as well as to broad applications.