• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.96-102
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• 2018

In this study, adsorption characteristics of coconut shell-based granular activated carbon (CS-GAC) on Basic Blue 3 (BB3) were evaluated. As the dosage of CS-GAC increased, the removal efficiency of BB3 tended to increase and the initial dye concentration of 50 mg/L was completely removed at 0.2 g dosage. Adsorption equilibrium achieved within 270 and 420 min at the initial concentrations of 25 and 50 mg/L, respectively, and the experimental data were represented by the pseudo-second-order model. The maximum uptakes ($q_{max}$) predicted by the Langmuir model were 34.45, 46.63 and 53.10 mg/g at 298, 308 and 318 K, respectively. The $q_{max}$ value increased as the temperature increased. Also, the Gibbs free energy (${\Delta}G$) was changed to -7.37, -8.19 and -10.40 kJ/mol with increasing temperature. The enthalpy change (${\Delta}H$) and the entropy change (${\Delta}S$) were 34.47 kJ/mol and 0.15 J/mol K, respectively. Therefore adsorption of BB3 by CS-GAC was spontaneous and endothermic.

• Membrane Journal
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• v.25 no.5
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• pp.406-414
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• 2015

In this study, partially fluorinated cation exchange membranes were prepared by direct sulfonation of Poly(VDF-co-hexafluoropropylene) copolymers (PVDF-co-HFP) followed by a casting method for application in the Membrane capacitive deionization (MCDI). The structure of sulfonated PVDF-co-HFP (SPVDF) was confirmed by Fourier-transform infrared (FT-IR) and $^1H$ Nuclear magnetic resonance ($^1H$ NMR) analysis. For quantitative analysis of the chemical composition, the X-ray Photoelectron Spectroscopy (XPS) was used. The membrane properties such as water uptake, ion exchange capacity and electrical resistance were measured. It was suggested that the optimum direct sulfonation condition of PVDF-co-HFP ion exchange membranes was $60^{\circ}C$ and 7 hours for temperature and duration of sulfonation, respectively. The water uptake of the SPVDF ion exchange membrane was 21.5%. The ion exchange capacity and electrical resistance were 0.89 meq/g and $3.70{\Omega}{\cdot}cm^2$, respectively. It was investigated that if it is feasible to apply these membranes in MCDI at various cell potentials (0.9~1.5 V) and initial flow rates (10~40 mL/min). In the MCDI process, the maximum salt removal rate was 62.5% in repeated absorption-desorption cycles.

• Resources Recycling
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• v.29 no.1
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• pp.17-24
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• 2020

In this study, rare earth elements (REE) leaching from a refractory REE ore containing goethite as a major gangue mineral was conducted, introducing a two-stage method of chemical decomposition-acid leaching. At the chemical decomposition step, using one of alkaline agent, NaOH, the ore was decomposed, changing NaOH concentration from 20 to 50 wt% at 10% (w/w) of pulp density and the maximum temperature achieved without boiling at each NaOH concentration. With increasing NaOH concentration, light REE (Ce, La and Nd) and iron were concentrated in the solid phase which is the decomposed product, while aluminum (Al) and phosphorus (P) were removed to the liquid phase, and their concentrations in the solid phase were down to 0.96 and 0.17%, respectively. In addition, through XRD analysis, it was found that the crystallinity of goethite was considerably decreased. At the acid leaching step, the product decomposed by 50 wt% NaOH was leached at 3.0 M HCl and 80 ℃ for 3 hr, then the REE leaching efficiency was above 94% (Ce 80%), and the leaching efficiencies of Al and P were decreased to 12 and 0%, respectively. Therefore, in terms of both REE leaching efficiency and impurity removal, those decomposition and leaching conditions were chosen as optimum processing methods of the investigated material. In terms of REE leaching mechanism, because REE and iron leaching efficiencies showed the positive correlation each other, so it can be concluded that decreasing crystallinity of goethite affect the improvement of REE leaching.

• Journal of Radiation Protection and Research
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• v.23 no.2
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• pp.109-114
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• 1998

Radiological safety for the conventional operation of Demonstration-Scale Incineration Plant (DSIP) was assessed on the basis of the results of trial burns using the simulated and real radioactive wastes. Radiation dose assessments for routine releases on an annual basis as well a several severe accidental releases on a short-term basis (2h) revealed that there would be no significant environmental impact when low-level waste Is incinerated in DSIP. For semivolatile radioactive cesium species, expected emission concentrations slightly exceeded 10% of maximum permissible concentration. Removal characteristics of the bag filter for condensed-phase cesium species was investigated by the trial burns of simulated waste with inactive cesium tracer. In the off-gas before passing through bag filter, distributions of condensed cesium species in the transition size ranging between the diffusional and inertial region are less than 5%. The overall collection efficiency of the bag filter for cesium species was higher than 99.9%, showing enough decontamination capability as a primary filter for the low-temperature dry off-gas system in radwaste incineration plant.

• Journal of the Korea Organic Resources Recycling Association
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• v.19 no.1
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• pp.109-114
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• 2011

This study was conducted to investigate the effect of hydraulic retention time(HRT) on the power density in a horizontal flow microbial fuel cell(MFC) reactor. When HRTs were 15min, 30min, 60min and 180min, maximum power densities were $24.7mW/m^2$, $27.3mW/m^2$, $22.8mW/m^2$ and $17.2mW/m^2$, respectively. The highest power density was obtained at HRT of 30min. It was 59% improvement when compared to the power density at an HRT of 180min. When HRT was increased, COD removal rate increased whereas the coulombic efficiency remained constant. The result shows that the optimal performance of the horizontal flow MFC reactor could be achieved at HRT of 30min.

• Journal of Electrodiagnosis and Neuromuscular Diseases
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• v.20 no.2
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• pp.98-105
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• 2018

Objective: To evaluate whether the increase of the amplitude of motor evoked potentials (MEPs) during surgery can imply favorable prognosis postoperatively in spinal cord tumor surgery. Method: MEPs were monitored in patients who underwent spinal cord tumor surgery between March 2016 and March 2018. Amplitude changes at the end of monitoring compared to the baselines in limb muscle were analyzed. Minimum and maximum changes were set to $MEP_{min}$ (%) and $MEP_{max}$ (%). Strengths of bilateral 10 key muscles which were documented a day before ($Motor_{pre}$), 48 h ($Motor_{48h}$) and 4 weeks ($Motor_{4wk}$) after the surgery were reviewed. Results: Difference of $Motor_{48h}$ from $Motor_{pre}$ ($Motor_{48h-pre}$) and $Motor_{4wk}$ from $Motor_{pre}$ ($Motor_{4wk-pre}$) positively correlated with $MEP_{min}$, suggesting that smaller the difference of MEPs amplitude, less recovery of muscle strength. There was a negative correlation between the amount of bleeding and $MEP_{min}$, indicating that the greater the amount of bleeding, the smaller the $MEP_{min}$, implying that MEPs amplitude is less likely to improve when the amount of bleeding is large. It also showed significant difference between patients with improved or no change of motor status and patients with motor deterioration after surgery according to anatomical tumor types. Conclusion: Improve of muscle strength was less when the increase of MEPs amplitude was small, and improvement of MEPs amplitude was less when the amount of bleeding was large. Correlation between changes of status of muscle strength after surgery and tumor types was observed. With amplitude increase in MEPs monitoring, restoration of muscle strength can be expected.

• Journal of the Korean Society for Environmental Technology
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• v.19 no.6
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• pp.536-542
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• 2018

A system combining an electrochemical method and an adsorption system using activated carbon was assessed to facilitate the reuse of cabbage-salting brine. IrOx/Ti insoluble catalyst electrodes were used in the experiment. The results were analyzed to identify any changes in the residual chlorine concentration according to variations in the current density at a salinity of 10 %, as well as the capacity of the activated carbon to adsorb the residual chlorine and organic matter. For current densities of $500A/m^2$ and $1,000A/m^2$, the residual chlorine concentration did not increase, instead stabilizing once the current reached 0.33 Ah/L. To assess the adsorption efficiency according to the residual chlorine concentration, the unit amount of the adsorption can be estimated from $Y=0.0066+2.087{\times}10^{-4}b$. For both residual chlorine generation using an electrochemical method and chlorine removal through activated-carbon adsorption, the unit amount of adsorption was 0.33 g/g. The maximum amount of $COD_{Cr}$ organic matter adsorbed by the activated carbon was 0.021 g/g, while for $COD_{Mn}$, the value was 0.004 g/g.

• Korean Journal of Environmental Agriculture
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• v.40 no.1
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• pp.40-48
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• 2021

BACKGROUND: Although the calcined oyster shell can be used as a calcium-rich adsorbent for phosphate removal, information about it is limited. The purpose of this study was to evaluate the phosphate adsorption characteristics and its mechanism using calcined oyster shells. METHODS AND RESULTS: In this study, calcined oyster shell (C-OS600) was prepared by calcining oyster shells (P-OS) at 600℃ for 20 min. Phosphate adsorption by C-OS600 was performed under various environmental conditions. Phosphate adsorption by C-OS600 occurred rapidly at the beginning of the reaction, and the time to reach equilibrium was less than 1 h. The optimal isotherm and kinetic models for predicting the adsorption of phosphate by C-OS600 were the Langmuir isotherm and pseudo-second order kinetic model, respectively, and the maximum adsorption capacity derived from the Langmuir isotherm was 68.0 mg/g. The adsorption properties of phosphate by C-OS600 were dominantly influenced by the initial pH and C-OS600 dose. In addition, SEM-EDS and FTIR analysis clearly showed a difference in C-OS600 before and after phosphate adsorption, which proved that phosphate was adsorbed on the surface of C-OS600. CONCLUSION: Overall, the calcined oyster shell can be considered as an useful and effective adsorbent to treat wastewater containing phosphate.

• Journal of Korea Foundry Society
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• v.43 no.6
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• pp.271-278
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• 2023

In the present study, A356 melt degassing experiments were conducted under various impeller rotation speed and inert gas flow rate conditions to determine changes in the melt temperature, composition and density during a degassing treatment. The melt temperature was found to decrease gradually as the degassing time increased, but a clear correlation between the impeller rotation speed or inert gas flow rate and the melt heat loss could not be confirmed. Regardless of the impeller rotation speed or inert gas flow rate, the Mg and Ti contents in the A356 melt scarcely changed, even after degassing for more than 10 minutes, while Sr contents decreased at the maximum degassing rate of 70 ppm. From a quantitative analysis of the degassing rate under each experimental condition based on the hydrogen concentration in the melt derived from the melt density and the degassing model equation, the inert gas flow rate was found to affect the degassing rate rather than the impeller rotation speed under the degassing operation condition employed in the present study.

• Land and Housing Review
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• v.15 no.1
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• pp.167-177
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• 2024

This study aimed to assess the efficacy of an adsorption process in removing organic matter and micropollutant residuals. After a full-scale water circulation system, the adsorption process was considered a post-treatment step. The system, treating anthropogenically impacted surface waters, comprises a hydro-cyclone, coagulation, flocculation, and dissolved air flotation unit. While the system generally maintained stable and satisfactory effluent quality standards over months, it did not meet the highest standard for organic matter (as determined by chemical oxygen demands). Adsorption experiments utilized two granular activated carbon types, GAC 830 and GCN 830, derived from coal and coconut-shell feedstocks, respectively. The assessment encompassed organic materials along with two notable micropollutants: acetaminophen (APAP) and acid orange 7 (AO7). Adsorption kinetics and isotherm experiments were conducted to determine adsorption rates and maximum adsorption amounts. The quantitative findings derived from pseudo-second-order kinetics and Langmuir isotherm models suggest the effectiveness of the adsorption process. The findings of this study propose the potential of employing the adsorption process as a post-treatment to enhance the treatment of contaminants that are not satisfactorily treated by conventional water circulation systems. This enhancement is crucial for ensuring the sustainability of urban water cycles.