• Journal of Korean Society of Water and Wastewater
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• v.24 no.1
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• pp.15-24
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• 2010

Coagulation can be used for pretreatment of NF membrane filtration. Foulants such as organic matter and particulate can be removed effectively with the process while high flux recovery is maintained. Recently various types of polyaluminium coagulants including polyaluminium chloride(PAC) are commercially available for water treatment. This study examines effects of polymeric Al and hydrolysis products of PAC on nanofiltration membrane performance. Dominant hydrolysis products were polymeric Al, $Al(OH)_3$, and ${Al(OH)_4}^{-1}$ at acidic, neutral, and alkaline pH conditions, respectively. Under acidic pH condition, flux decline was increased with increasing PAC concentrations, possibly due to polymeric Al adsorption on membrane pore and/or surfaces. For neutral and alkaline pH conditions, little flux decline was observed with increasing PAC concentrations except the highest ${Al(OH)_4}^{-1}$ concentration, with which rapid flux decline was shown. Removal of ionic matters was also varied with pH conditions in this study. Especially, conductivity removal was substantially low and $Ca^{2+}$ concentration in the permeate was quite high at neutral pH condition.

• Journal of Microbiology and Biotechnology
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• v.28 no.3
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• pp.432-438
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• 2018

Microalgae hold promise as a renewable energy source for the production of biofuel, as they can convert light energy into chemical energy through photosynthesis. However, cost-efficient harvest of microalgae remains a major challenge to commercial-scale algal biofuel production. We first investigated the potential of electrolytic water as a flocculant for harvesting Tetraselmis sp. Alkaline electrolyzed water (AEW) is produced at the cathode through water electrolysis. It contains mineral ions such as $Na^+$, $K^+$, $Ca^{2+}$, and $Mg^{2+}$ that can act as flocculants. The flocculation activity with AEW was evaluated via culture density, AEW concentration, medium pH, settling time, and ionic strength analyses. The flocculation efficiency was 88.7% at 20% AEW (pH 8, 10 min) with a biomass concentration of 2 g/l. The initial biomass concentration and medium pH had significant influences on the flocculation activity of AEW. A viability test of flocculated microalgal cells was conducted using Evans blue stain, and the cells appeared intact. Furthermore, the growth rate of Tetraselmis sp. in recycled flocculation medium was similar to the growth rate in fresh F/2 medium. Our results suggested that AEW flocculation could be a very useful and affordable methodology for fresh biomass harvesting with environmentally friendly easy operation in part of the algal biofuel production process.

• Journal of the Korean Chemical Society
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• v.17 no.6
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• pp.416-423
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• 1973

Formation of the complexes of alkaline earth metal ions with malonate and o-phthalate ions in aqueous, ethanol-water and acetone-water solutions (20% by volume) was studied at room temperature by the equilibrium ion exchange technique. This technique involved the measurements of distribution of radioactivity between cation exchange resin(Ion Exchange Resin CGC 241) and solution phases after the radioactive metal ions were equilibriated with the cation exchange resin in the presence of malonate or o-phthalate ions of varying concentrations. The pH of the solutions was controlled to 7.2~7.5, and the ionic strength of the solutions was kept at 0.10~0.11. The results of the present study indicated that the alkaline earth metal ions formed one-to-one complexes with the dibasic organic acids in all solvent systems examined. The present study showed that the relative stabilities of the complexes increased in the order: $Ba^{++}\;<\;Sr^{++}\;<\;Ca^{++}$ complexes. It was also observed that the relative tendency of the o-phthalate ion for the complex formation was somewhat greater than that of malonate ion in each solvent system. Furthermore, it was noted that the complexes were formed more readily in the mixed solvent than in the aqueous solution.

• Advances in Energy Research
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• v.2 no.1
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• pp.21-31
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• 2014

The use of a microporous membrane along with Au/C catalyst for direct glycerol alkaline fuel cell was investigated. In comparison with Nafion 112, the microporous Celgard 3401 membrane provides a better cell performance due to the lower ionic resistance as confirmed by impedance spectra. The single cell using Au/C as anode catalyst prepared by using PVA protection techniques provided a higher maximum power density than the single cell with commercial PtRu/C at $18.65mW\;cm^{-2}$ The short-term current decay studies show a better stability of Au/C single cell. The higher activity of Au/C over PtRu/C was owing to the lower activation loss of Awe. The magnitude of current decay indicates a low problem of glycerol crossover from anode to cathode side. The similar performance of single cell with and without humudification at cathode points out an adequate transport of water through the microporous membrane.

• Journal of the Korean Ceramic Society
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• v.56 no.6
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• pp.541-548
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• 2019

Zirconia (ZrO₂) materials are widely used in a variety of energy systems and devices. When nanorod-shaped ZrO₂ is used as energy materials, ionic conductivity and mechanical strength can be improved compared to the characteristics of conventional spherical-shaped nanomaterials. In this study, we synthesized ZrO₂ nanorods and investigated the shape change of them depending on various synthesis conditions such as precursor concentration, synthesis temperature, synthesis period, and aging period. The obtained nanorods were casted into a membrane for alkaline water electrolysis system and subjected to basic performance evaluation for use as a separator. The structure and the shape of the nanorods were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and the like.

• Korean Journal of Environmental Agriculture
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• v.24 no.2
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• pp.98-105
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• 2005

Groundwater sampled from 24 tube wells of three districts namely Sherpur, Gaibandha and Naogaon in Bangladesh was appraised for their water quality for irrigation and agro-based industrial usage. All waters under test were slightly alkaline to alkaline (pH = 7.2 to 8.4) in nature and were not problematic for crop production. As total dissolved solid (TDS), all groundwater samples were classified as fresh water (TDS<1,000 mg/L) in quality. Electrical conductivity (EC) and sodium adsorption ratio (SAR) values reflected that waters under test were under medium salinity (C2), high salinity (C3) and also low alkalinity (S1) hazard classes expressed as C2S1 and C3S1. As regards to EC and soluble sodium percentage (SSP), groundwater samples were graded as good and permissible in category based on soil properties and crop growth. All water samples were free from residual sodium carbonate (RSC) and belonged to suitable in category. Water samples were under soft moderately hard, hard and very hard classes. Manganese, bicarbonate and nitrate ions were considered as major pollutants in some water samples and might pose threat in soil ecosystem for long-term irrigation. For most of the agro-based industrial usage, Fe and Cl were considered as troublesome ions. On the basis of TDS and hardness, groundwater samples were not suitable for specific industry. Some water samples were found suitable for specific industry but none of these waters were suitable for all industries. The relationship between water quality parameters and major ions was established. The correlation between major ionic constituents like Ca, Mg, K, Na, $HCO_3$ and Cl differed significantly. Dominant synergistic relationships were observed between EC-TDS, SAR-SSP, EC-Hardness, TDS-Hardness and RSC-Hardness.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.338-341
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• 2004

This study was carried out to understand the geochemistry of saline water circulating in an ash disposal pond of Seocheon power plant, Korea. For this study, ash pond waters, slurry water and seawater samples were collected and analyzed for major ions and trace elements. Results show that ash pond waters and slurry water are alkaline in nature due to high calcium content, and have high concentration of Ca, B, Li, As, Ba, Al, Si and Mn over seawater, suggest that these elements leached from fly ash even at high alkaline condition and ionic strength. Slurry water has high concentration of B, Ba, Li, Mn, Si and Sr compare to ash pond waters, expresses that these elements seem to be easily reached at initial stage fly ash-water interaction, and also might be associated with the surface of the fly ash particles. Additionally, PHREEQC program predicted several secondary solid phases, which are also influenced in the leaching of elements in to the saline water.

• Journal of Hydrogen and New Energy
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• v.33 no.4
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• pp.372-382
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• 2022

In this study, anion exchange membranes were prepared by synthesizing the main chain into a poly(arylene ether) (PAE) structure, and the structures capable of improving the physical and chemical stability of the membrane by introducing a heterocyclic quaternary ammonium functional groups were studied. The chemical structure and thermal properties of the prepared polymer were confirmed by ¹H-NMR, FT-IR, TGA, and DSC, and surface analysis was performed through AFM measurement. Additionally, dimensional stability and chemical properties was studied by measuring water uptake and swelling ratio, IEC and ionic conductivity. At 90℃, the quaternized poly(arylene ether) (QPAE)/1-methylpiperidine (MP) membrane exhibited the highest ionic conductivity of 27.2 mS cm^-1, while the QPAE/1-methylimidazole (MI) membrane and QPAE/1-methylmorpholine (MM) membrane exhibited values of 14.5 mS cm^-1 and 11.5 mS cm^-1, respectively. In addition, the prepared anion exchange membrane exhibited high chemical stability in alkaline solution.

• Journal of Soil and Groundwater Environment
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• v.16 no.4
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• pp.31-37
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• 2011

The feasibility study of soil flushing was investigated to remediate lubricant oil and zinc contaminated railway soil. In this study, mixed washing agents of surfactant and inorganic acid/base were used for the simultaneous removal. The mixed washing agent of non-ionic surfactant and HCl removed 15% of the lubricant oil and 40% of zinc, respectively. Alkaline-enhanced soil washing process increased the removal of lubricant oil up to 40%. This is because alkaline solution reduced the interfacial tension between water phase and lubricant oil phase due to the soap formation reaction. To simulate in-situ soil flushing for the remediation of railroad-related contamination, two dimensional soil flushing was carried out based on the results of batch soil washing. In the soil flushing, the removal efficiencies of lubricant oil and zinc were 34% and 16%, respectively. Even though the removal efficiency was low, the mixed washing agent can remove metal and lubricant oil simultaneously.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1145-1152
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• 2013

The rate constant of alkaline fading of methyl green ($ME^{2+}$) was measured in the presence of non ionic (TX-100), cationic (DTAB) and anionic (SDS) surfactants. $ME^{2+}$ hydrolyses and fades in neutral water and in this work we search the effects of surfactants on its fading rate. The rate of reaction showed remarkable dependence on the electrical charge of the used surfactants. It was observed that the reaction rate constant decreased in the presence of DTAB and SDS and increased in the presence of TX-100. Binding constants of $ME^{2+}$ to TX-100, DTAB and SDS and the related thermodynamic parameters were obtained by classical (or stoichiometric) model. The results show that binding of $ME^{2+}$ to TX-100 and DTAB are two-region and that of SDS is three-region. Also, the binding constants of $ME^{2+}$ to surfactant molecules in DTAB/TX-100 and SDS/TX-100 mixed solutions and their stoichiometric ratios were obtained.